Low rpm's 90 Yamaha

[bcribb52]

Thanks Rodbolt for sending me to a real mechanic. I had my 2004 Yamaha 2 stroke 90 HP motor dyno tested like you told me to do and it tested good. The service man at Page's Creek Marine told me that the motor ran perfect but the prop which is an after market ss prop looked to be to big, the blades were wider than a Yamaha prop. He suggested I put a 17 yamaha prop on the motor and it would most likely get the rpm's up to the 5200-5400 range. The after market 17 ss prop I had on it turned up 4200 rpm's. I also tried another after market 15 ss prop and it turned up 4900 rpm's,this was before the dyno testing. I should have the new Yamaha prop on this week so I'll post the results of that performance after the test run.

 

[WillyBWright]

Re: Low rpm's 90 Yamaha

Couple of questions for you. What brand(s) and had either ever been reworked?

 

[lonewolf5347]

Re: Low rpm's 90 Yamaha

Corona Time <br />I did reprop my 2003 90 yam from the factory prop that came with the engine.I did find with the factory prop it took forever to get on plane,it did WOT around 5500 rpm.I can't tell you the numbers on the new prop the boat is up north ,right now I am down here in calabash N.C.<br />I did go with a michiagan match prop and lost a little on top end ,WOT around 5200 but get on plane at 1800 rpm instead of the 3200 rpm with the old prop.The 90 HP yam is on a 18 ft seapro CC

 

[bcribb52]

Re: Low rpm's 90 Yamaha

I'm not sure what brand the prop is but it is a polished stainless steel prop.Its brand new and has not been worked on.The dealer who sells the prop says he puts that prop on all of his motors. I'll find out the brand and re-post it later. I'm still kind of concerned to whether or not the 17 yamaha prop is going to get the rpm's up like it should be. I can't find anyone who has a prop I can try before I buy one.Any suggestions?

 

[lonewolf5347]

Re: Low rpm's 90 Yamaha

http://www.marinedepo.com/proschool101.html

 

[Searun1]

Re: Low rpm's 90 Yamaha

I have a 90 HP Yamaha as well. It came propped with a 13 x 19 Yamaha aluminum. I had to reprop the engine as I wasn't getting past 5000 rpms at WOT. It is my understanding that the boat hull shape and weight will determine what the proper prop should be and that their won't be one perfect prop for the engine. With my V-hull 16 foot boat a 13.25 x 17 Yamaha aluminum has it running great with quick planing and proper WOT range.<br /><br />I am not an expert though so take it with a grain of salt. This is just my experience. I wanted to reprop with a SS prop and gave up as I don't want to spend a ton of money to experiment to find the right one.<br /><br />SeaRun1