prop problems

[paul74]

needing help ive got a Chris craft scorpion 21ft it has been fitted with a ford transit engine 2.5td fully marinised the stern drive is a mercrusier alpha 1.
When i bought the boat a few months ago i took it out recently and only got about 4-5 knots took the prop off to find serial numbers on was for a outboard i have bought a mercrusier 17pitch prop and still get the same need help with prop with thanks paul

 

[Lyle29464]

Re: prop problems

not sure if we are being had but here goes.

If your engine RPM is turning anyplace between 1500 and 4400 you have a spun engine coupler or your still tied to the dock. The only other thing that can slip is the hub in the prop and you have changed that. If your engine will not turn thousands of RPM it is the problem.

 

[paul74]

Re: prop problems

not sure if we are being had but here goes.

If your engine RPM is turning anyplace between 1500 and 4400 you have a spun engine coupler or your still tied to the dock. The only other thing that can slip is the hub in the prop and you have changed that. If your engine will not turn thousands of RPM it is the problem.

coupler fine , prop fine had locked into gear and tried to turn no movement seems .just got a 15 pitch hope that works if no think its the gear ratio hope not!!!

 

[NHGuy]

Re: prop problems

2.5TD eh? What does it rev to? Do you have an idea of what torque it does? Chances are you need extra tall gearing due to the low end torque and lower red line than a gas engine. In Alpha ones I have seen a list that only goes down to 1.30 as I recall. You will need a tall prop too. I'd be looking at 21 or 23 pitch, but that's a guess.
Wait for someone with more knowledge than I.

 

[Bondo]

Re: prop problems

has been fitted with a ford transit engine 2.5td fully marinised the stern drive is a mercrusier alpha 1.

Ayuh,.... Never heard of your Motor,....
Where did the Drive come from,..?? What motor was it originally coupled too,..??

 

[NHGuy]

Re: prop problems

American light truck turbo diesels tend to have somewhere around 100 foot lbs torque per litre of displacement. So guessing from that maybe your engine is pushing 200 or 275 foot lbs. I'd think-guess you should be able to see 35 or more mph with things optimized.