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Difference in aircraft vs GPU motors?

R

rost495

Well-known member
Starting to look, hoping to buy a reasonable airboat by late next summer or sooner.

I am still convinced I want an aircraft motor, and would really prefer a Lycoming 0540 since thats what my buddy has..... would make sense anyway... BUT I'm not averse to what is good.

Which brings up reading on GPUs I'm fairly sure I know what they were/are. But are they exactly the same as an aircraft engine, mags, seperate jugs, updraft carbs on bottom etc... so that working on them would be the same as continental/lycoming?

Any negatives to them? Any specific positives?

And the RPM is correct, IE I won't need a reducer?

Thanks, Jeff AND Happy New Year to all if I don't get back till then!
 
They are the same to work on as aircraft but alot cheaper.You can also convert them with aircraft jugs and duel mag them.They run on pump gas.The only draw back is they do use oil if they are worn.You wont need a gear box. Hope that helps.
 
If you can afford it the 540 is the way to go. I'd say an injected angle valve would do all that the average recreational user needs to do. A GPU comes set up with a single magneto and one plug per cylinder. They do have individual freestanding cylinders, but the induction is downdraft. In my opinion the single ignition is a negative point, however the heads can be machined for the 2nd plug and the cases can be set up to accomodate driving the additional magneto. On the other hand, I see the downdraft intake as a positive. Conversions to automotive carburators are common and seem to work well. Continental's fuel injection system can also be adapted to these engines with good results. an additional adapter will also be needed on the crank flange in order to fit a propeller, The GPU crank has one bolt offset to prevent attaching a propeller to it. I once had a built up GPU with dual ignition, fuel injection, High compression pistons, etc..., it didn't hold a candle to the larger displacement Continental A/C engine that I currently have on the same boat. Besides being more powerful, it turns about 700 RPMs less than the GPU at normal cruising speed making it significantly more economical to operate. Theres lots of GPUs out there giving good service, but they won't do what a "big inch" motor ( 540 or 520 )will do. At the same time, they aren't gonna cost as much to purchase. Just my humble opinion, hope it helps ya' some!
 
The best way I can describe the difference between a GPU and an aircraft. The basically are the same as far as parts interchanging (cylinders etc) The biggest difference is this. Look at a truck, lets say a dodge truck, you can buy a 1/2 ton truck. Its good for the road and off road and does what you need. Now Go look at a 1 ton dodge. Looks like the 1/2 ton but when you really start looking you see the parts are better (stronger ) on the one ton (running gear, chassy etc.
So thats the difference.
GPU is a 1/2 ton ----it does the job but the parts are not as strong as an aircraft. It was used on the ground as a generator. NOTHING wrong with it just NOT HEAVY DUTY

Now look at an AIRCRAFT---HEAVY DUTY 1 TON PARTS--built for the air and built to last--STRONGER PARTS

Thats the difference oh yea plus a ground power is ALOT CHEAPER and you can put aircraft parts on it (cylinders,rods etc)
 
Thanks for all the input, I"m learning slowly, and thats what I wanted to do.

Happy New Year to All!

Jeff
 
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