Propeller

[Pmon]

Hello. I’m new to boating and I’m trying to find out if my boat has the correct propeller on it. The engine is a 5.7l omc V8. It’s about 20 ft long. The propeller on it at the moment is 141/2x 19 3 blade. But if I have any weight on the boat it struggles to get up on plane. It’s not a new prop it has a few chips on it. Would that be the problem or is it just to high of a pitch. I want to buy a new prop but do I buy the same one that’s on the boat or change it? I’m not made of money so I don’t want to be wasting it in the wrong prop. Thanks

 

[Scott Danforth]

First, welcome aboard

A 19p would actually be fine if not underprop'd with a healthy motor?

Start with a compression test

 

[Pmon]

First, welcome aboard

A 19p would actually be fine if not underprop'd with a healthy motor?

Start with a compression test

Thanks. Compression test is all good. All up around 175 psi

 

[Scott Danforth]

Thanks. Compression test is all good. All up around 175 psi

You need to check your gauge or you have oil in each cylinder

A new motor will have 150 psi. To get 175 psi, you would need to have a compreasion ratio of 12.5:1 (that is drag motor territory, boat motors are 9.4:1 or less)

 

[Pmon]

You need to check your gauge or you have oil in each cylinder

A new motor will have 150 psi. To get 175 psi, you would need to have a compreasion ratio of 12.5:1 (that is drag motor territory, boat motors are 9.4:1 or less)

 

[Pmon]

The boat is 1984 so I’m guessing the engine is around the same age. I tried two different gauges and got the same results. It’s just very sluggish fully loaded.