Marine Engine Building, Is It For You? - Engine Builder Magazine

Marine Engine Building, Is It For You?

Engine builders who do passenger car and light truck engines, diesel engines and performance engines, are often looking for new market niches where they can expand their business and add new customers. For some, marine engine building may seem like a tempting niche.

The marine engine market is relatively healthy, though highly competitive. Some rebuilders estimate the size of the marine engine market to be fairly small, perhaps less than 130,000 engines per year, including all types of inboard and outboard engines. Even so, the market appears to be growing and poised for even more growth in the years ahead.

According to the National Marine Manufacturers Association, over 72 million people own some kind of a motorized boat or watercraft. Over the next decade, more people will be entering the 40-and-older group. These are the people who have the disposable income to buy boats, and more importantly marine engines. Many of these people are into serious power boating and think nothing of spending $20,000 to $80,000 or more on a serious, high performance big block marine engine – and some of these boats run two engines! As one marine engine builder said, “There are a lot of million dollar boats on the water these days.”

Those who cater to this niche also say that the high end of the marine engine market seems to be absolutely recession-proof. The big boys who have big bucks to spend on their toys are spending more and more every year to be a little faster than the next guy. The boats are also getting bigger (and heavier), and that means a need for even larger and more powerful engines.

Many of the engines that are find their way into offshore performance boats are monsters with 600 or more cubic inches of displacement. Many of these engines are also supercharged or turbocharged and develop upwards of 1,200 hp on pump gas (93 octane). Fuel injection is used on 80 to 90 percent of these engines, and many are running custom marine camshafts that alter the firing order between cylinders 4 and 7 to smooth out the idle characteristics of the engine.


Though a marine engine would seem to be pretty much the same thing as an engine for a car or a truck, marine engines are a different breed of motor according to those who build them. Marine engines work a lot harder than automotive engines, experiencing much higher loads. It’s like permanently hooking up a heavy trailer behind your car or truck and driving around in 4th gear. Stern drives typically have 1:1 gear ratios, so the engine has to pull much harder compared to an automotive engine that has gear reduction in the transmission, and addition gear reduction in the differential.

The typical marine engine in a pleasure boat might spend 10 percent of its time idling, maybe 60 percent of its running time at cruising speed (4,000 rpm), and maybe 10 to 30 percent of its time running at wide open throttle (5,500 to 6,500 rpm). A performance boat might spend 5 percent of its time idling, and 95 percent of its running time at wide open throttle at speeds as high as 8,000 rpm.

Because of these loads, marine engines don’t last like automotive engines. An engine in a pleasure boat might go six or eight seasons before it needs to be rebuilt. An engine (or pair of engines) in a big offshore boat, on the other hand, might go 200 to 250 hours before they need work. That’s the equivalent of a car engine needing an overhaul every 12,000 to 15,000 miles!

The operating environment for marine engines is also entirely different. The engine is in a boat, which means it usually relies on the surrounding water for coolant. Consequently, there are no corrosion inhibitors in the coolant and cooling system corrosion is a major issue. All the fittings have to be stainless steel, brass or some other corrosion-resistant material. With an offshore boat, the situation is even worse because the coolant is salt water. The highly corrosive nature of salt water means the cooling jackets inside the cylinder block and heads must be painted or coated to prevent the salt from eating away the metal.

Cooling is a major issue with marine engines, even stock ones. Inboard engines are typically located low in the hull where there is little if any airflow around the motor itself. Fresh water engines often run quite cool (120° to 145° F), which can cause the rings and valves to gum up. An engine operating temperature of 160° to 180° F is better because it allows the engine to develop more power and experience less blowby (and less cylinder wear). But with salt water engines, going over 150° to 160° F may cause the salt to precipitate out of solution and form scum deposits inside the engine.

Marine engines typically use water-cooled exhaust manifolds to preheat the incoming water, and to keep the manifolds from getting so hot they create a potential fire hazard inside the boat. But the exhaust manifolds are also very vulnerable to internal corrosion. If the cooling inlets, cooling system and exhaust outlets are not cleaned and maintained regularly, they can clog with corrosion and debris causing the engine to run hot, overheat and suffer damage such as scuffed pistons, valve sticking or head gasket failure.

The wet nature of the marine environment also precludes the use of a lot of electronics on the engines. Though many engines are now running fuel injection, the engine control module runs in open loop because no oxygen sensors are used in the exhaust manifolds. Some high performance engines do run digital pyrometers in the exhaust to keep an eye on exhaust temperatures so they can avoid running too hot and too lean (which may be too bad for the engine!). But most of the tuning that’s done is done in the shop on a dyno, and once the engine goes out the door there’s little if any adjustment that’s possible.

Reliability is a big issue with marine engines, too. The last thing any boater wants is a dead engine miles from shore. You can’t exactly call AAA to come give you a jump start or tow your boat to the nearest garage for repairs. If you’re lucky, the Coast Guard or another boater will come to your rescue. And if you’re not lucky, you might end up in Davy Jones locker. Arrrr….


Nobody knows for sure how many machine shops are actively involved in marine engine building, but most of those who do marine engines have been in the marine market a long time. Most also have a loyal customer base, and many have a personal interest in boating. Some started out in traditional automotive machine shops while others have always done marine engines and little else. Locality often plays a key role in marine engine building. If you’re close to water, you usually have a potential market nearby. Even so, many marine engine builders sell their engines far beyond their local or even regional markets. Even some automotive PERs such as RECON and Jasper have found success rebuilding and distributing marine engines nationally.

One thing every engine builder we interviewed for this article agreed upon was that marine engine building is pretty much of a specialty. There are some shops that do both automotive and marine, but the majority of those who are into the marine market do marine only and nothing else. That includes inboard and stern drive engines as well as outboards (which are even more of a specialty).

“Guys who rebuild car engines hardly ever make good marine engine builders,” said Bob Teague of Teague Custom Marine, in Valencia, CA. “Marine engine building takes an entirely different mind set. There aren’t a lot of guys who are doing high performance marine engines, maybe only a dozen or so who really know their stuff.”

Teague says he is probably the largest builder of high performance marine engines other than Mercury. He builds big block Chevy engines that range in power from 620 to 1,450 horsepower. All his engines are sold complete, ready to install.

“Our least expensive motor is $25,000, and our most expensive is $68,000. We do about 125 new engines a year, and probably half than many rebuilds. We make all our own hardware for these engines, including anodized fittings and brass water lines.”

Teague said before he builds an engine, everything for that engine application is blueprinted and machined in-house. In other words, the engine and everything that goes on it is all custom built for a particular boat. There’s no such thing as an “off-the-shelf” engine or a “crate engine” for his kind of customers. Every engine is unique and built to the customer’s exact specifications.


Tommy Hofstetter of Chief Engines in Ft. Lauderdale, FL said is business is strictly inboard stern drive engines. “Probably 99 percent of the engines we’re doing today are over 600 cubic inches displacement, and 90 percent are fuel injected. Our engine prices range from $35,000 up to $125,000. Most of these are for offshore boats.”

“Marine engine building takes an entirely different thought process than automotive engine building. You need to put more emphasis on making the engine stronger and more durable. So we use all billet steel components, things like the crankshaft and rods.”

Hofstetter said turbocharging is the current trend in high output engines. Supercharging used to be the way to go, but with electronic controls a turbo can deliver more power as just as reliably as a blower. But turbos are expensive. The ECU alone for a turbo setup costs $7,500, and the whole system adds about $15,000 to the cost of an engine. Even so, the results are worth it. “We’ve built marine turbo motors that can produce 2,000 horsepower and run at 8,000 rpm.”

Hofstetter said he guarantees all his engines for 90 days, which is usually enough for a summer or boating season.


One shop that has had success with both automotive and marine engines is Auto Marine Engineering in Glendora, CA. Tom Label says his shop has been doing automotive repairs and marine engines since 1973. They specialize in complete service for stern drives, “V-Drives” (Casale, Menkens and Hallcraft) and “Jet Drives” such as Bay, Berkeley, Dominator, Jacuzzi, Panther and American Turbine. They do it all in-house, and can also fabricate obsolete parts that may be unavailable.

One of the keys to their success is stocking a wide variety of standard marine equipment and boating supplies, from boat anchors and bilge pumps to boat waxes and just about everything in between.

Label said his business is geared mainly for inland lake and river boats, but he also services much larger offshore boats.

“For over twenty years, we have had hands-on experience with winning drag boats, circle boats, ski race and endurance boats. This experience has given us the knowledge to develop superior designs, and fabricate superior components for all types of boats, and for a wide variety of uses,” said Label.

“Building custom race and pleasure boats is more than a business with us, it is a passion. Every engine and every piece of hardware that we fabricate for our customers is proudly hand crafted to exacting specifications. Our quality is second to none.”

Label said many marine engines today are running fuel injection instead of a carburetor, and many older engines are being retro-fitted with aftermarket electronic fuel injection systems. This has created an opportunity for also doing fuel injection service, including flow testing and matching injectors for maximum performance.

Another engine builder who has had success in both automotive and marine markets is Greg Hekimian at Hekimian Racing in Watertown MA. He estimates about 40 percent of his business is marine. The rest is mostly automotive high performance.

“We do engines for all kinds of boats, including air boats, and we do engines for drag cars, oval track cars, dirt track cars, street cars and even some vintage Lola 302 Chevy engines.”

Hekimian credits much of his success with high performance engines to the fact that he learned a lot about coating technology while working on military projects in his former career as a materials engineer. “We use up to 17 different military spec coatings on engine parts for various purposes, and also have our own in-house cryogenic treatment equipment for treating parts. The equipment uses liquid nitrogen to chill parts down to -320° F. This changes the microstructure of the metal making the parts stronger, more reliable and also smoother at a microscopic level.

“We also design our own custom camshafts, and switch the firing order of cylinders 7 and 4, and also 3 and 2 on our big block Chevy marine engines. The 7 and 4 cylinder swap helps even out fuel distribution in the manifold and is good for 8 to 22 hp depending on the cam overlap and lift. Switching the firing order of 3 and 2 helps smooth out engine balance.”

Hekimian said ring sealing is an issue with marine engines, so he has his own custom ring sets made. The ring sets are expensive ($300 to $400 per set) but they solve a lot of problems.

“With all the things we do to our engines, the engines will usually run 300 to 600 hours or go five to six years before they need any work. You don’t see the customer for a long time, but he’s certainly happy with the results and tells others who built his engine.”


Getting into marine engine building isn’t as simple as hanging up a sign that says “We Do Marine Engines,” and then sitting back and waiting for the customers to line up at your door. First you have to know something about the variety of different marine engines (inboards or outboards, or both) that are out there, including where to find parts and service information for these engines.

You also have to learn how marine engines are machined differently from automotive engines. Because marine engines typically work harder, tolerances have to be closer, valve seats have to be wider, and higher grade parts have to be used throughout the engine for the engine to last.

There’s no substitute for experience, say those who build marine engines. You really need to be heavily involved with this type of work to do it well. You can’t just do an occasional marine engine and expect it to last. Experience comes with time, and some things you have to learn the hard way.

If you don’t know anything about marine engines, the American Boat & Yacht Council (ABYC) offers seminars and certification programs including gas and diesel marine engines. These courses have nothing to do with machine work, but are a good introduction to the basics of marine engines. Their “Basic Marine Engines” seminar runs 3 days and covers gasoline and diesel engine troubleshooting, fuel systems, ignition, inboard and outboard drives, and more. The cost is $495 for members, and $695 for non-members. See for more details.

Another source of information (and potential employees for marine installation and repair work) are votech colleges that offer marine programs. There are a handful of such programs around the country, including:

  • Marine Mechanical Institute in Orlando, FL (, which is now run by the UTI Corp., the same people who have the NASCAR technical
    training school.

  • WyoTech’s marine engine program in Daytona Beach FL (

  • East Central Technical College in Fitzgerald GA

  • New England Institute of Technology (

  • Wisconsin Indianhead Technical College ( with various locations in Wisconsin.

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