Automotive Engine + Transmission

I am thinking about building a mahogany runabout with a jet instead of a prop and am looking for ways to save on cost. (I am thinking about doing it myself over a year or 2) I had an idea of finding an automotive engine (old or the car was written off) and super-charge it. But I have read that automotive engines are no reliable in marine applications because they need to be run at high rpms for long periods of time. So my question is... Is it possible to run an automotive engine with a transmission (to reduce the RPM) or is moving all that water to much for the engine to handle higher gears?

 

Sure, you can marinize most car engines. It's just that sometimes this costs more than an existing marine engine, or the car engine will have to be detuned a lot in order to not blow it up, or both. Multi-speed gearboxes are sometimes used on big heavy boats, or race boats, but they don't really reduce the load on the engine- they just move it to a different point on its power/RPM curve, that may be better suited for the application.

 

It seems to me that there ought to be a LOT of information out there for marinizing the more popular auto engines (e.g., Chevy 350, Ford 351, etc) and I'm sure there's even a few kits. This could be a very attractive option, especially for vessels on a smaller lake or kept near shore. These engines can be picked up at a local salvage yard for $500 or so. Of course though, if you want the ultimate in reliability, you'll pay for it one way or the other...

 

Technically with a jet, you don't need a gear box - you can just 'find' neutral with the bucket, although the boat does tend to wander a little. With a gas engine in particular, you can just switch it off to stay still. Depends on how you plan to use your boat; for water skiing it would be a pain, but as a run around it would work.

 

Go to Hotboat.com http://www.hotboat.net/index.php. Click on Forums. You will find an over abundance of people who do what you are talking about. For the most part these engines are in very fast boats, v-drive, jets and a few straight drives. By mounting the engine in the open they circumvent some of the marinizing that has to be done for a regular inboard engine. Many of these ar eusing blowers and some even use nitro but I wouldn't want to go there. Check it out. (oh yeah, you'll have to register just like here but it's free now.)

 

Well on of my original intentions was full economy (less RPM = less gas... right?) and the cost of salvaging an automotive engine would be less then trying to find a marine equivalent. But it looks like break-neck speeds might be an additional bonus.