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Converting from car engine to aircraft.

R

Roweboat

Member
I have a 15ft rivermaster hull with rod boxes with a 425 cadillac DD. I just purchased an continental o-470 e185, would this engine benefit my boat performance or would it be a waste of time and money converting it over?
 
15' is a bit big for an aircraft conversion from the DD caddy, I would suggest selling the E185 and buy a gearbox and a bigger prop.
 
You will save a bit of weight and possibly gain a bit on thrust. Combined the difference won’t move a rivermaster out of the river.
 
I guess my thought process was the ac motor has 20 more hp. It is 470 cubic inch verse 425 cubic inch. I would also imagine that it weighs 200lbs less. All i am saying is the torque to weight ratio would be much better. my boat now, doesnt run dry very well.
 
You’re thinking is correct, but the difference will not be as significant as you hope. That is a big, heavy boat. The point is that you are gonna put a lot of work into a new engine stand etc, don’t set your expectations too high.
 
Do think it would be enough push to run on grass or to stop on the middle of a sand bar and take off loaded.
 
My friend has a Lazer hull with a 220 GPU and he says it will go anywhere he points it but I would guess the laser is much lighter. He claims that the e185 is better than the 220 gpu. Your thought?
 
Yes, the e185 is an aviation motor with dual mags and plugs and a bearing system made to swing a prop. GPU's were made to turn generators at 1,800 RPM. The e185 is tuned to prop speed and rated 205-225 Hp and about 360 lbs depending on details. Loosing 200 lbs is roughly equivalent to gaining 25 hp as far as performance. You seem to think the old caddy is tired, what prop (including diameter and pitch) are you running now? What RPM does it turn maximum on the trailer?
 
i am running a Sensenich 72' Q, on the trailer i don't know, but boat sitting on the ground 3000 rpm.The prop is in the middle of the 3 settings so technically i could give it slightly more pitch to turn 2850. The caddy motor is a 1978, it never goes much over 160 temp but every time i turn it off it wants to diesel not sure if the motor is weak or the timing is to far advanced.
 
That is good information and shows that the engine is reasonably strong. The e185 is NOT going to turn more prop than that without modification, probably a bit less pitch. The conversion would net you a decrease in weight, not a bad thing, but not enough to achieve your goals.

Run on is common, particularly hot shut downs, I doubt it reflects low compression. Run a compression test and see what you find. Get a fuel shut off solenoid valve at the carb inlet and shut off fuel and let it run until the bowl is empty.

Do you know how much the rig weighs now?
 
My experience was a 74 inch Q was the better Caddy length. Your L33 / 425 sounds strong for stock?

Have you tried letting it idle for a "full minute" prior to shut down?

What is the idle rpm? Factory spec was 500 rpm

How do you have it timed? (Fatal error to push advance in a Caddy)

Try adding in a little Marvel Mystery oil, use good Premium fuel and let it idle a full minute before you turn it off. At about the 20-30 second mark stab the gas pedal once or twice to squirt fuel into her that cools and makes her stumble. If you have an electric fuel pump turn it off 10 seconds before turning off the key.
Really loose engines will have run on sometimes due to carbon, timing and rotating mass.
 
If engine runs on check that carb butterfly's are properly adjusted (most are not) and if you have a power valve make sure it is not blown.
 
Thank you for all the feedback. In the winter it always gives me time to think about how to make my boat better. I have owned since 2008 and it has been a turn key ang go everytime, since I have owned I have painted it, put new poly on it, upgraded the exhaust and cooling system, and put a rebuilt quadrajet carb with spacer and the sensenich q, it originally had a wood 72x34. The prop was the biggest improvement out of all. I just purchased that continental motor thinking it was a better power plant with not as much fabrication needed, but after researching I am off on my figures. In the case of me selling the a/c and buying a 1.73 gear or belt drive is this going to give me the push that I am searching for. In this case what would the rpm be at cruise and what the top engine rpm be with the throttle completely open, and would that caddy hold together.
 
I talked to sensenich a couple of years ago and they suggested a 82" R for that application now if that is the case it would obviously be the better option if my motor can withstand the extra rpm. I haven't a clue what that motor is rated for as far as that.
 
OK I CONVERTED FROM A 350 AND GEAR TO A 300HP VO540. I Say I still want more power but I currently don't have the cash to put the gear box back on my vo540 (new crank prop gear.) So I say you wont like that big boat with that little motor. if you rebuild the cad and put a gear box on it you might like that better.
 
To make your 16 foot boat do what you are asking, it is going to take something with a gear box and a whole new prop. I will leave it to the caddy guys to chime in, but the advice is that you don’t just take a stock caddy (new or used), put on a gearbox and expect it to hold together for long.

The low end of a properly built gear box caddy is $8,500 with warranty and goes up from there. Gear and prop is another $6-8K new. It can certainly be done for less if you have the knowledge and ability.

My preference is smaller and lighter. That e185 on a 12 foot hull will make you grin.
 
If you had a 13ft boat and a 1.7 drive you would be very happy. Going to a 16ft and putting weight in it requires something upgraded if you plan to run any dry loaded.

At a minimum to go on a drive you need to upgrade the timing set and get a shaft rocker system. Even doing that your at a bare minimum as your running a cast piston in a long stroke engine. Do your self a favor and call the Wizard 352-797-9910
 
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