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Propeller question

wicked salmon

wicked salmon
in This Old Boat

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  • 4 weeks later...
rolmops

rolmops

Posted
Posted (edited)

That is completely dependent on  your payload,trimtab position and weather . Presuming  that you run a 350 with 260 hp, your rpm seems a bit low. But it could be because of your timing setting or the cleanliness of your hull. There really are too many things that play a role. Besides, sometimes people prefer to over prop or under prop in order to get a better rpm for trolling.

Edited by rolmops
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Xxx

Xxx

Posted
Posted

I have a 22ft Sea Ray cuddy and I blew my lower unit in the early part of May, the mechanic over in Henderson told me I should run a 17" prop, and he also saw my stainless steel prop and said we love you guys that run those props they keep us in business. He told me to get a aluminum prop, they break long before damaging the lower unit, way to many rocks this end of town for a steel prop. I was very surprised as I thought the stainless was the way to fly, not according to the man that repairs them, so I bought a aluminum one and kept the steel one for a spare.

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  • 2 months later...
Xxx

Xxx

Posted
Posted

Mercruiser has a prop size calculator on line, the prop your running is what I'm running, but I have a 22fter with a 350 Mercruiser that was rebuilt by my uncle as he has a speed shop, that specializes in dirt modified race cars my motor is bored .30 over which makes it a 355ci, with very good heads and a 260hp marine cam. With a 500cfm Holley "2" barrel carburetor, I did this so I could use the original intake, to keep my linkage " shift & throttle " the same. I had a 21" prop on that prop I couldn't get on plane for a long time. Then I tried a 15"x15" she jomped out of the water but I was pushing 4800rpm at 23mph. Then I tried a 17x15 which works the best for me, it still stood up in the front but got on plane quick and at 3500rpm which seems where everything works the best I get 28-30 mph. I also added trim tabs to cure my hole shots now the nose stays down and I gained a few mph's. The tabs were one of the best things I put on the boat!! So a 17"X 15" did the best for me, my boat is heavy.

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rolmops

rolmops

Posted
Posted

You might want to bring the pitch down to a 14. That will raise your RPM by about 200,so from 3400 to 3600  which will bring it in the low normal,but a good hull cleaning or different weight distribution might have the same effect. all other things being equal going down from 15 to 14 will improve performance a bit.

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Xxx

Xxx

Posted
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My motor is balanced, and your right I usually tour around at 28-3200 rpm, less gas longer motor life. Take today's motors in cars way better put together than a older 350cid and your over the road rpm's is 12-1600rpm, that's how they get 150,000 plus before things start to go down hill.

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rolmops

rolmops

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Posted

I stopped by the boat and measured the prop. On it was printed- rh17 and 15. So right hand rotation and 17 degree pitch. 15 is the diameter. Is that correct and do you guys think that is the correct propeller for this boat.

Sent from my SAMSUNG-SGH-I747 using Lake Ontario United mobile app

I just read this again and I am wondering. Usually a propeller is marked with the diameter first and the pitch last. In your case that would mean that you have a 17 inch diameter and a 15 pitch. This would make for a work boat pushing prop. Most Penn yans would have a 15 inch diameter prop.

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Chas0218

Chas0218

Posted
Posted (edited)

I just read this again and I am wondering. Usually a propeller is marked with the diameter first and the pitch last. In your case that would mean that you have a 17 inch diameter and a 15 pitch. This would make for a work boat pushing prop. Most Penn yans would have a 15 inch diameter prop.

I agree my prop is a 15x17 15" diameter with 17" pitch. I highly doubt you have a 17" diameter prop I don't think it would fit under the cavitation plate. That being said it seems like you have what most people are running on the same sized boat. 

 

Here is a question for you, how many hours on your motor? Have you done a compression test lately?

Edited by Chas0218
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L&M

L&M

Posted
Posted

Unless I'm missing something.  I haven't seen yet in this thread weather it,s a straight inboard of which most 26 Pro's were or an I/O. Propeller's and sizing are entirely different between the two.

 

disregard  :)   We were both replying at the same time

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