Posts Tagged ‘marine engines’

I love my boat but the engines are on their last leg. Should I try and upgrade with new engines, or just sell the boat and start over?

This is one of the most common questions boaters are faced with today when its comes to replacing the engines in older model boats. There are a number of factors to consider when replacing the engine, so this Selection and Shopping Guide will help you drill down to see what option best fits your boat’s situation. It’s important to realize how the 2010 Marine Engine EPA regulations changed the overall topic of replacing the engine, so this is something every boat owner needs to be aware of.

• 1) Do you want a complete Bobtail Engine, Power Package Motor or just the Longblock?
• 2) Do you want a New Marine Motor or Remanufactured?

*SHOP ONLINE*
BOBTAIL ENGINES	POWER PACKAGE (PAR PAC) ENGINES	LONGBLOCK ENGINES

Selecting the Correct Model of Marine Engine for Beginners and/or Novice Boaters

There’s no shame in finding it difficult to distinguish one model 454 Marine Engine from another. Over the years the various marine manufacturers have changed both V6 and V8 engine models so many times it can be difficult even for Marine Engine distributors to properly identify the correct engine model for a customer. Typically, verifying the Engine Casting Number (link to block casting number location) along with the Cylinder Head Casting Number (link to head casting number location) is the best way to identify your Marine Engine correctly. Providing customers with solutions is where PPT stands above the other Marine Engine suppliers in providing technical assistance and information to help you properly determine the correct motor model for your application. PPT maintains a A+ rating with the BBB for one simple reason; WE TAKE CARE OF OUR MARINE ENGINE CUSTOMERS! Don’t be fooled by other Marine Engine retailers advertising 7 year warranties or 30% better fuel economy; those are simply gimmicks. The bottom line with Replacement Marine Engines is that you get what you pay for.

Marine Engines Technical Library

Topic: Replacement Options

Question: Why is it so difficult to find a remanufactured marine shortblock? I see plenty of new and remanufactured longblocks but not any shortblocks.

Response:

There are a variety of options to be considered when replacing the engine in marine applications. Depending on the severity of the issue that’s driving your need to replace the engine here are a few things to consider. You can also read our technical articles regarding overall repowering options to research the advantages versus dis-advantages of drop in bobtails versus longblocks. 

Definition: Shortblock 

• Shortblock’s have been offered in the past as either new or remanufactured product.
• Shortblock’s include the block and rotating assembly but NOT the cylinder heads.
• The primary purpose of Shortblock’s is to offer the “cheapest” engine replacement option.

Definition: Longblock (read more on the terminology of longblock versus bobtail, etc.)

• Longblock’s are currently offered as either new or remanufactured product.
• Longblock’s include the block and rotating assembly AND the cylinder heads.
• The primary purpose of Longblock’s is to offer the “most cost effective” engine replacement option.

Summary Explanation

It’s important to remember that cheaper is not always better when repowering your boat. Whether you consider new or remanufactured the better option to consider would be what offers the best value. While shortblocks are almost always going to be cheaper on the front end versus a longblock they may not necessarily be cheaper in the long run. This leads us to the overarching reason of why the Marine Industry has all but moved away from offering the shortblock engine options. Warranty cost is a huge factor that the manufacturers are building into the up front cost of the products when they are sold. The more complete the engine is when sold to the customer the less likely it is that the customer will experience warranty related issues. By far the vast majority of warranty problems customers experience when repowering is caused by something they install improperly, installing incorrect accessories, etc. With this in mind it’s important to realize that one of the driving factors determining the longevity of any replacement Marine Engine is the marine cylinder heads they are equipped with. The cylinder heads are a huge factor in dictating the overall performance which also has a huge affect towards the engines suseptibility at ingesting water. Another extremely important factor is the condition of the valve seating, etc which affects both performance as well as the water ingestion and reversion characteristics.

Last but not least is the manufacturers ability to test the product which is being provided to the customer. In the case of a marine shortblock the product cannot be fully tested for compression, fluid leakage, performance, oil pressure, etc. Even in the case where test heads are installed for the purpose of test running the engine the performance, compression, head gasket leaks, etc being verified are not valid for the actual engine that ultimately gets installed into the customers boat. The reason being since the heads have to be removed on shortblocks after testing and ultimately get repalced by whatever the customer choose to install.

Final Conclusions

Our best recommendation is to pay a little extra up front and purchase a true Marine Longblock. The up front cost difference is really not as great as one would think because the testing required for shortblock’s requires more labor at installing and then having to remove components. Therefore some of the cost saving you would expect are in fact eaten up by additional labor cost. This small up front cost of the longblock buys you exponentially lower industry reported warranty rates versus that of the shortblock’s. In our experience, in the longrun we’ve found the longblock will generally cost even less than the shortblock.

SHOP FOR LONGBLOCK’S NOW

The model of Mercruiser Engine can be determined by looking at the last letters of the engine code which is stamped in all complete Marine Longblocks by General Motors at the time of assembly. If the serial number and/or model decals are missing, the Marine Engine code will help to determine the specific engine model/vintage. Refer to the drawing below for the engine code location of your Engine.

Information you need from the engine code, example M01187MH. 7=General Motor’s model year in this case 1997, BUT this could also be 1987 or 1977. MH = Type of engine. The 350 cid V8 Mercruiser models 5.7L, 350 Mag Mpi, Black Scorpion Ski, etc.

**GM 6 Cylinder 250 cid (4.1L) – Sterndrive Model (LH rotation), flat lifters

**GM V6 229 cid (3.8L) – Sterndrive Model (LH rotation), flat lifters

GM V6 262 cid (4.3L) with Mechanical Fuel Pump – Sterndrive Models (LH rotation)

**GM V6 262 cid (4.3L) Gen II with Electric Fuel Pump – Sterndrive Models (LH rotation), roller lifters

**GM V6 262 cid (4.3L) Gen+ – Sterndrive Models (LH rotation), roller lifters and rocker arms

Go Directly to the V6 Longblocks in the Store………V6 Marine Longblocks 

The model of Mercruiser 3.0L 4 Cylinder Engine can be determined by looking at the last letters of the engine code which is stamped in all complete Marine Longblocks by General Motors at the time of assembly. If the serial number and/or model decals are missing the marine engine code will help to determine the engine model. Refer to the drawing for engine code location.

Information you need from the engine code, example M01187MH. 7=General Motor’s model year in this case 1997, BUT this could also be 1987 or 1977. MH = Type of engine. The 350 cid V8 Mercruiser models 5.7L, 350 Mag Mpi, Black Scorpion Ski, etc.

GM 4 Cylinder 153 cid (2.5L)

Sterndrive Models (LH rotation), flat lifters

GM 4 Cylinder 181 cid (3.0L) with 2–piece Rear Seal

Sterndrive Models (LH rotation), flat lifters, 3.0L cyl. Head

GM 4 Cylinder 181 cid (3.0L) with Full Circle Rear Seal

Sterndrive Models (LH rotation), flat lifters

Go Directly to Marine Longblocks in the Store……….3.0L Marine Longblocks

Our Remanufactured Marine Longblock Engines have a Max bore size of .060″ over. The normal manufacturing process includes cutting .040″ then checking cylinder wall finish, and if needed cutting another .020″ maximum. NOTE – All of the cylinder bores will be the same diameter.

People generally have a misconception of  cylinder bore that more is bad, which is not necessarily true. While a .060 bore or .040 for that matter has less “meat” in the cylinder walls than it started with originally-it does not negatively affect engine performance or longevity. GM’s OE cylinder wall thickness varies from engine model to engine model..and even from block to block depending on casting shifts..or mold design. The production process for our remanufactured longblocks monitors casting shifts and uses a type of ultrasound machine to measure thickness to make sure it is in our allowed range on questionable blocks.

BOTTOM LINE: Cylinder Wall Thickness is more important than how much the cylinder is bored out.

Using the links below you can review more information regarding changing out a longblock. Let us know if you need any further technical information, we will be glad to assist!

Link to Block Code/Serial Number Location

Link to Remanufactured Longblock Options

Link to Remanufacturing Tech Video

Marine Products How-To Articles Library

Our Technical Boating Library features a wealth of information for both novice and veteran boating enthusiasts, including easy-to-follow how-to videos and valuable articles. Search for the information you need by category, then select the associated topic to find answers to common boating related questions. Whether you’re looking for articles on replacing a Marine Engine, Quicksilver Marine Parts or propeller fundamentals you will find it at PPT. However, if you still can’t find the information you need in our library, please don’t hesitate to contact us via phone or email (405) 533-3812 or [email protected]. Our experienced and friendly staff is always available to answer your questions and guide you down the right path, from finding the right Yamaha marine parts to installing a wakeboard tower.

Performance Product Technologies offers more than 50 combined years of technical experience and knowledge in the boating and marine parts industry. We understand the design and engineering of everything from long block engines to Volvo marine parts and accessories, making us a reliable source for insight and advice on the best parts and options for your boat and boat engine.

 GENERAL 

When it comes to engine horsepower versus torque in marine applications, most people make the common mistake of focusing on horsepower rather than the torque. When it comes to both gas engines as well as diesel engines, in most cases focus should be directed to the torque more so than the horsepower. There is a common saying with in the OEM industry that “Horsepower sells a boat however Torque is what actually moves it”. This could not be closer to the truth! One should realize that horsepower is really a measure of the torque over a given period of time. This taken into account by the rpm variable in the specification. The following equation may help to shed some light as well.

Torque = Hp x 5252 / Rpm (5252 is a constant)

It is interesting to note that the formula also verifies the typical torque bell curve when the torque trails off as rpm increases at the top end. One may consider that engines making torque at a lower rpm tend to work better in marine applications due to the fact that “most” boats tend to plane in the range of 2,000 – 3,000 rpm. It’s not by chance that most marine engine manufacturers continue using the larger displacement – lower rpm, cast iron marine engines because of this fact. Many people wonder why these manufacturers haven’t changed over to the high rpm engines the automotive industry has been converting to over the past 10 years; for the same reason the LT-5 Corvette engine and Lexus V8 engines didn’t work very well in these marine applications — nice Hp but at higher rpm’s and therefore poorer low rpm torque characteristics.

Another interesting item to note is that since the proper method for propping a boat is to select the size prop that allows the engine to turn at it’s maximum allowable rpm. It is required that a similar level of torque be produced at the top rpm condition as well as the proper planing rpm for a given boat hull (draw a straight line across the torque bell curve and see at what “lower rpm” this takes place. If this is not the case the selected prop will over-load the engine at the boats planing rpm and therefore yield very sluggish low rpm performance characteristics. For example a high revving engine that makes 400 hp at 5500 rpm would be making about 382 Lb-Ft torque (using the above formula) at 5500 rpm, since it would have a maximum torque output at probably 4,000 rpm it would be likely not to produce enough torque at 2500 rpm to make the boat plane very well since the prop was selected based on the 382 Lb-Ft value. Notice the higher the rpm an engine makes it’s torque the worse this situation becomes.

In contrast to this; large engines that make significant horsepower at “very” low rpm’s will therefore make a tremendous amount of torque, but at extremely low rpm. For example a diesel marine engine that makes 300 Hp at 2,000 is making 788 Lb-Ft at this same rpm. Noting that the torque curve is generated in “bell form”, and therefore the maximum torque could be as high as 900 Lb-ft on this 300 Hp engine. Comparing this against a 300 Hp GM small V8 engine that makes 300 Hp at 5,000 and 375 Lb-Ft torque at 3200 rpm, this is a considerable difference. Very low rpm diesel engines typically make tremendous low rpm torque and therefore require specific gear ratios not supported by sterndrives, as well as requiring much larger diameter prop shaft’s.

APPLICATION
Since overall boat speed is generated by a combination of prop speed and prop pitch (the horizontal distance traveled by a single propeller revolution – measured in inches. Ex 21P means 21 inches of travel with one revolution). For most mid-size boats (up to 40 feet) the best option is a higher revving diesel engine that generates torque at lower rpm. For example a diesel engine that produces 300 Hp at 3600 rpm and makes 500 Lb-Ft torque at approximately 1600 rpm will work out much better than the example above of the 300 Hp engine making it’s power at only 2000 rpm.

BOTTOM LINE
When looking to re-power spend as much if not more time focusing on the torque rather than horsepower.

STEP #2 UNDERSTANDING THE TERMINOLOGY FOR YOU BOAT REPOWER PROJECT

After getting a handle on the EPA guidelines for repowering as we covered in STEP #1, the next thing is to get make sure you fully understand the terminology that’s used to describe the different marine propulsion products and options. The listing below is not all inclusive but does detail the the most commonly used terms used when determining how to power your boat. It’s extremely important to understand the difference between a longblock vs a short block engine, what is considered as standard rotation for a marine engine, what is a bobtail engine, etc. Fully understanding these terms and descriptions will put you in a better position when you start talking with the suppliers, and buy a replacement boat engine or the parts and accessories that will be needed to complete your boat repower project. (Select blue hyperlinks below to read more detail with each topic)

Engine Rotation….(Read More) – No matter whether you choose a longblock, power-package or complete turnkey bobtail engine the rotation of the motor is a critical item to know. Rotation with marine engines is always viewed from behind the engine looking towards the engine flywheel. Within the Marine Industry “Standard Rotation” (left hand) means the flywheel is turning counter clockwise looking at it from the rear of the engine, or another way to think of it is that the harmonic balancer will turn clockwise when standing in front of the engine to view it. “Opposite Rotation” engines (right hand) were common years ago however they have not been regularly produced today because the newer models of transmissions (Hurth & Velvet Drive) both have negated the need for this since the transmissions can rotate either direction without issue.

Marine Engine Longblock….(Read More) – This is a great value based option for boaters with freeze damaged motors, or in the event that you experience any general engine failure but are not in the position to buy a completely dressed out turnkey bobtail engine. The term “Longblock” generally refers to the cylinder block & heads as well as the required internals of the engine which are called the rotating assembly of the engine. Longblocks being classified as non-complete engines are therefore not currently regulated by the EPA as the new complete turnkey bobtail engines are. Marine Longblocks are therefore NOT forced to come equipped with a Marine Catalyst System.

Generally these marine longblocks do not include the intake manifold, engine circulating pump, or flywheel however this does vary when comparing new vs remanufactured longblocks. Depending on the brand of the longblock product and whether it’s a new or remanufactured longblock it may be supplied with the “Tin Ware” (oil pan, valve covers, timing chain cover) as well as some of these additional accessory items. Unless it is specified up front the remanufactured longblocks are almost never supplied with the “Tin Ware”, however new longblocks are normally supplied with the “Tin Ware” as well as the flywheel and harmonic balancer. The reasoning behind this variation in the content that is supplied with the longblocks comes down to cost control. The flywheel, balancer and tin ware are not considered to be items that normally wear out and need to be replaced. Therefore, the remanufactured longblock manufacturers do not include these items.

NOTE: Please be aware that Marine “Shortblocks” are no longer available. The primary reason behind this was that the cost difference between a longblock versus a shortblock was insignificant versus the significantly higher number of warranty issues that resulted with shortblocks. The two primary reasons for the higher number of warranty issues was driven by the fact that the shortblocks cannot be fully tested after manufacturing like the longblocks can. The other reason was that when existing cylinder heads that have valve seating issues were installed onto a new shortblock it almost always causes serious longevity issues to the engine which is out of the direct control of the manufacturer.

IMPORTANT: When repowering your boat by replacing the longblock it should be noted that none of the manufacturers will cover warranty for ANY water ingestion related failures. Therefore, if you are replacing a longblock due to freeze damage you need to either be 100% sure your exhaust system (Read More…) is not cracked, or it is simply recommended to just replace the exhaust to be safe. We also recommend replacing your engine coupler (Read More…) whenever replacing the longblock. The coupler is an item with a specified life span since it transfers the power from the engine to the sterndrive or transmission. The coupler is much like a clutch in a manual transmission automotive application and it can only be replaced while the engine is out of the boat.

Power Package….(Read More) – These products are also referred to as Par-Pac’s which is short for “Partial Package”. These terms all refer to the growing market for partially completed engines. These range from new longblocks with the marine fuel and electrical systems already installed, but due to the EPA Guidelines they do not include the exhauust systems as that would require them to be supplied with Catalyst Systems. Just like the New Longblock products detailed above, Power Package’s are classified as a non-complete engines and therefore they are not regulated by the EPA like the New Completely Dressed Bobtail Engines. Therefore, the Power Packages are NOT forced to come supplied with a catalyst system. The main selling point of the Power Packages is that they work great for the customer needing a replacement engine product, but most of their ancillary accessories are still in good shape and don’t need to be replaced.

Two other great applications for the Marine Power Package are when you are replacing a 5.0L and want to the larger displacement and performance of the 5.7L engine, or when you are replacing an older pre-1996 260 Hp 5.7L and want the additional performance offered by the 300 Hp Vortec 5.7L engine model.

Bobtail Marine Engine….(Read More) – This term generally refers to a new or remanufactured, completely dressed “turnkey” engine. NEW Bobtail Engines require more hurdles to jump over due to the EPA Repowering Guidelines as outlined in STEP #1 of the Boat Repowering Guide. Depending on the manufacturer of the product in question these “Bobtail” products generally come complete with fuel, electrical, cooling, and exhaust systems as well as the engine mounts and bell housing which makes “Bobtail Engines” ready to drop right in when replacing completely “worn out” engines. Turnkey bobtail engines are classified as complete engines so as of 2010, NEW Bobtail Engines are in fact regulated by the EPA and now forced to be supplied with a catalyst system (Read More).

In an effort to combat the introduction of the EPA regulations in 2010 MerCruiser introduced their PLUS Series (Read More) and CPO product lines (Read More) for Bobtail Marine Engines, Sterndrives and outboard motors. All of these product lines have proven to be be extremely successful since their introduction. For the obvious benefit of working around the EPA issue that requires the catalyst system and controls, the CPO and PLUS Series product lines now makes up the vast majority of repowers that require a completely dressed motor to be used. When the condition of the existing engine in your boat you are replacing dictates that a complete bobtail engine is required, you will first need to determine if the existing engine drive coupler can be used, and then if the existing sterndrive or transmission will couple directly to this. In many cases, if the engine you are replacing is more than 15 years old you will likely have to change out the main engine electrical harness connection plug because these have changed over the years. It is also common on these 15+ year old engines for the exhaust system to have changed since the exhaust systems went changed from 3 inch to 4 inch outlet designs to accommodate the increasing levels of engine output.

Complete Package – This term refers to the combination of a New, Completely Dressed Bobtail Engine, and in the case of a Sterndrive Package it would include the Transom Assembly/Shield (sometimes also referred to as the Gimbal Assembly) along with the Sterndrive. For Inboard Packages it would include a New Engine and the Transmission. Select this link to read more about Sterndrives versus Inboards.

“Complete Packages” is a term that is normally reserved only for NEW products, and NOT the CPO or PLUS Series lines of remanufactured marine products. You could put together a “Complete Package” using either the CPO or PLUS Series products or a combination of remanufactured and new, however you would have to separately purchase the trim pump, exhaust Y Pipe and a few other additional accessory items to match the same level of content that is/was supplied with the “New Complete Packages”.

NOTE: Most manufacturers do not sell Complete Packages today rather they sell everything a la carte between the engine, sterndrive, transom assembly and/or transmission. You still end up with an all New Complete Package in the end, however unlike it was in the past you have to piece the package together item by item by selecting the specific engine + sterndrive + transom assembly.

Sterndrive….(Read More) – This term refers to the drive or propulsion system on Inboard/Outboard powered boats. Therefore, this labels teh drive system itself which incorporates an engine inside of the boat, along to a drive unit that mounts onto the transom and is located outside of the boat. The different sterndrive designs used to power these “Inboard/Outboard” boats can utilize either single or dual propeller drive designs.  Two manufacturers; MerCruiser & Volvo Penta make up roughly 99% of all the OEM sterndrive sales worldwide.

Transom Assembly….(Read More) – Also referred to as the gimbal assembly or transom shield in the case of Volvo Penta products this term refers to the connection point between the engine and sterndrive on Inboard/Outboard powered boats. The transom assembly includes both a plate that mounts on the inside of the boat and incorporates the rear engine mounts. The transom assembly also includes the exterior portion you see visibly on the outside of the boat. The transom assembly contains the sterndrive bell-housing and is what allows the range of motion necessary for the drive to not only steer from left to right but also the upward and downward articulation. Since the transom assembly is teh connection point of the engine and sterndrive it is also what the main alignment point between the engine and drive by way of the “Gimbal Bearing” Checkout the following article and video regarding proper drive/coupler alignment….(Read More).

Transmission – Also referred to as the gearbox, this is the drive system on inboard powered boats. These typically come in different gear ratios and also different output flange angle configurations as required by specific prop shaft angles. These output flange variations include inline, down angle and V-drive configurations.

Select this link to read more about Inboard Drive Variations.

Helpful Hint – Be aware that most early twin engine powered inboard boat models used the cast-iron-body version of the Borg Warner Velvet Drive transmissions. These transmissions were then used in combination with 1 standard rotation engine and 1 opposite rotating engine. With the early version Twin Engine powered boats there were very few options available for the propshaft angle. Therefore the engine had to be installed such that the crankshaft was also at the required prop shaft angle. In the early 1990’s the bi-directional ZF Hurth and Velvet Drive 5000 series aluminum body transmissions were introduced which very quickly negated the need for opposite rotating engines. Therefore if you are looking to repower an older boat that includes the above described engine & transmission setup with a completely dressed bobtail engine, this creates an issue due to the fact that the newer style transmissions do not share the same mounting configuration but the newer engines do not offer an opposite rotation model. Therefore, you get stuck having to rework the stringers in the boat to accept the newer style transmission mounts and position.

RETURN TO BOAT REPOWER GUIDE MAIN PAGE

PPT is proud to offer you the most thorough and engineering supported technical advice when it comes to re-powering your boat with either new or remanufactured marine longblocks, complete bobtail drop-in motors or MerCruiser Sterndrives. Due to recent changes within the marine industry we suggest reviewing the 4 steps and technical information outlined below. Once you complete reviewing this guideline, we would be happy for the opportunity, and do our best to help you with your project by answering any specific questions that arise.

Don’t make the mistake of purchasing any Original OEM Mercruiser Engine, Transom Assembly, or Sterndrive from a non-authorized Mercury dealer. Your warranty may depend on it! If a warrant-able technical issue arises you want the support of an authorized Mercury Mercruiser dealer working on your behalf. PPT is proud to be a Platinum Level Mercury Mercruiser dealer while also offering more than 20 years designing and patenting products for many of the features and accessories the Mercruiser engines are equipped with. Purchase your Mercruiser engines and Products from the People you Trust!……Read More

STEP #1 – Understanding YOUR BOAT REPOWERING OPTIONS regarding THE NEW 2010 EPA RULES

Beginning in 2010, the EPA began requiring that CERTAIN NEW ENGINES used when repowering boats to be equipped with emissions control, or use of an specific engine model that is excluded from the EPA requirements….Read More

STEP #2 – Understanding the most common BOAT REPOWERING TERMINOLOGY

One of the first and foremost items for Boaters to get a handle on is the terminology that’s used to describe the different available product options. This library is not all inclusive but addresses the most commonly used “Boat Repowering Related” terms…..Read More

STEP #3 – Determining the CONFIGURATION of Your Existing ENGINE & DRIVE

Next you will need to determine or understand whether you have a sterndrive or an inboard configuration model….Read More

STEP #4 – Determining AGE & SERIAL NUMBER of Your Existing ENGINE

This is important in helping to determine what specific product options are available for replacement. In many cases the serial number contains specific information from the manufacturer that will be important when re-powering to make certain you match the model correctly….Read More

MerCruiser Boat Repower Guide (Read More)