which prop for newbie

[doryfishin]

hi , i have a 13ft dell quay dory with a 1974 20hp mercury thunderbolt outboard , what size prop with what pitch should i get , it came with a 2 blade 10" prop but wont rev out so im thinkin 3 blade but dont know what i should get any pointers would be much appreciated .

 

[steelespike]

Re: which prop for newbie

If you read the stickies at the top of the page you'll better understand prop selection and how to get the most out of your question.If you can be more specific we could tell better where the problem is.
The 3 blade will perform better all around but a 2 blade could be faster.
More than likely if it won't "rev out" there is something up with your motor
If the boat is meant plane it shouild be running at at least 20 to 25 mph.
Is the prop a 10" pitch or is that the diameter.My frirst thought is missing one cylinder next a fuel delivery problem.

 

[doryfishin]

Re: which prop for newbie

hi , thanks for the reply . the prop is 10 inch diameter but has 7 3-8 stamped on it , i measure it as 10 but the markings would refer to it as a 7 ? . i have good compression on both cylinders fuel is good tryed squeezing bulb when working throttle but does nothing , yet in the test tank it will rev and in neutral it will rev .

 

[doryfishin]

Re: which prop for newbie

bump

 

[steelespike]

Re: which prop for newbie

Reving in the test tank doesn't really mean anything. Check the plugs.
Should be brownish black not wet.If you run it say for a minute if one cylinder is dead that plug will likely be cooler.See if it responds to a little choke.
If its a 10 X 7 prop it should leap when you hit it and the motor would scream if healthy.Might not go real fast.but motor would be wound tight.