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Bilge Brothers' Bio
Syndication for October 2006


Diesel from Gas Engine Change Over
Diesel envy, we all have it. It’s that feeling you get when you pull up behind that Cabo 50 as it’s idling down the channel with a quiet rumble. There are a million reasons to go to diesel, but we’re not going to cover those here, you’ve made up your mind and that’s that. So, after the decision’s been made, what’s really involved?
First, find the right person to do the swap. If you’re changing from high horsepower gas inboards to higher horsepower diesels, there may be structural changes which should be handled by a fully qualified yard. For a single stern drive, a really good dealer can handle the change. And if you’re handy with tools, and have a well equipped garage, one company can sell you an engine that you and a buddy can easily drop in over a weekend.
Of course, we must consider the physical size of the power package; will it fit in the existing space or will a bulkhead need to be moved? How about engine bed width? How does the weight compare to the out-going power? Will there be adequate room and accessibility to perform maintenance on the new power? These are some of the first things to consider.
Another matter often overlooked, but critical to the operation and safety of your installation, is the volume of fresh air available in your engine room. Diesels use much more combustion air than gas engines of the same horsepower and with turbo housings and after-coolers generate a lot more radiant heat. Diesels also need cool air to make their rated horsepower, so engine room air flow becomes very important. Other considerations are fuel line sizes, filters and adding a fuel return line.
Once we’ve got air coming in, we’ve got to get exhaust out. Diesels produce larger volumes of exhaust gases and need to evacuate them efficiently. This may mean going from out drive to through transom exhaust. It may also mean an increase in exhaust pipe diameter, and perhaps different mufflers.
The engines are ordered, but how are we going to get that power to the water? Diesels top out at a lower RPM than gassers, so a prop change is a given. And what about all that torque? For inboards, it’s wise to buy the transmission and engine as a unit as the gear ratios will be correct and the torque capacity will be compatible. A heads up though, you may need to increase your prop shaft diameter. If you’re running a stern drive, you’ll probably want to upgrade that as well. Mercruiser and Volvo both have dedicated diesel stern drives, and agreements with other engine manufacturers who can deliver a package. On a custom setup, you may want to check out Konrad Marine for a drive so indestructible Uncle Sam uses them on his boats.
The last thing to consider is a perk of engine replacement. Most diesel re-powers come with new instrument panels. There are some pretty fancy panels out there, all designed to slip right into place on your helm.
Who are the players in the re-power arena? Yanmar, Cummins Mercruiser, Volvo and Cat all offer inboard and stern drive re-power packages in the 200 – 700 horsepower range. A good option for smaller boats running a single engine or medium horsepower twins is Marine Diesel. These guys can also sell you a Mercruiser diesel out drive, but depending on model and condition, your current drive may live quite a while behind one of the lower horsepower choices. The wiring harness plugs right in and your existing gauges will work just fine.
Getting rid of your diesel envy might take a bit more than just writing the check, but trust us, it’s worth it.

(Photo Caption)

MarineDiesel’s line of V8 footprint Diesel power plants tops out with the Tigershark—a 400 HP screamer.


Fuel Flow Meters what are they good for?

Since every boat is equipped with a fuel gauge, you may be wondering why you need a fuel flow meter. Above normal fuel consumption can be an indicator of a fouled bottom, a damaged prop, a weak engine or slipping transmission. Knowing the rate you’re consuming fuel also reduces the potential for running dry ‘out there’. A flow meter, when coupled with GPS via NMEA 0183, will tell how much fuel you’ve used, and how far until your next stop. A series 9000 from Floscan, or a Cruisemaster 5500 will make your boat safer and more reliable.


Q: Edelbrock has come out with a conversion kit for throttle body to EFI on cars. I queried the tech if they could be put on boat motors and he said yes. For twins, one motor is counter clockwise and they have a chip for the computer in the kit to deal with this. Has anyone done this? Could there be ugly ramifications to my motors if I was to install these? I have “87 350 crusaders. Any reply is welcomed.
Thanks,
Two Many

A: Hey Two many,
This can be a great upgrade if done correctly. The bennies are reduced fuel consumption, and extended maintenance intervals. Because the EFI allows a cleaner burn you see less fuel dilution in your oil, especially if you do a lot of low speed trolling, plus much better starting when cold. Critical here is the quality of the install. Because the EFI requires relatively high fuel pressure, it’s critical from a safety stand point that the fuel lines be properly constructed from materials rated for this duty. This means no rubber hose, no clamps. It does mean A/N fittings, braided stainless or hard line. Remember, cars can leak fuel and not blow up, boats can’t. Never take chances with fuel leaks on your boat. Another caveat, some fuel injection systems require a line to return un-used fuel to the tank. It may be necessary to remove the tanks to install the proper fittings. Might be expensive.
Some fuel injection setups come with a distributor and wiring so that the computer which controls the fuel can also control the spark. If you decide to install this type of system, be sure the new distributor is ignition protected and meets the appropriate standards in that area. That said, we think it’s a great idea.