Prop for Yamaha 225

[jeuto]

I have a 25 Cobia center console and it is rigged with a single 225 Yamaha, the prop was in bad shape so I had it worked on and when it was done they said it was changed from a 16 pitch to a 17 but it needs to be 19? What is the correct prop size and pitch for a set up like mine? Does anyone know what the RPM operating range is for a boat/motor combo like mine? It cruises around 25 knots at about 4500 rpm is that around where it should be (1/3 tank of fuel and 2 people)?

 

[moderator1]

Re: Prop for Yamaha 225

Moving to prop topics and questions....

 

[walleyehed]

Re: Prop for Yamaha 225

With a normal load, you should be near 6000RPM at wide open throttle.<br />Your RPM range is 5000-6000.

 

[jeuto]

Re: Prop for Yamaha 225

I think it gets to about 5500rpm at WOT, I should of paid more attention to it. So my motor should be at 5-6K at WOT. What about cruise? Gas is a little high now so efficiency is on my mind, so based on that statement what is a reasonable estimate for a cruise RPM range?

 

[walleyehed]

Re: Prop for Yamaha 225

Most of the 2-strokes are around 3500-3800 for best economy..it changes a bit with each boat, even 4000 would be OK, as long as you are able to attain the top of your RPM range, as in 6000.<br />If the prop shop said it needs to be a 19 and 5500 is all you get at WOT, your prop shop is incorrect.<br />What model of tachometer do you have? OEM?<br />The shop can test your tach against their shop tach if needed to verify accuracy.<br />Was the prop that you had worked, a stock aluminum prop?

 

[jeuto]

Re: Prop for Yamaha 225

Thanks for the reply, my prop is stainless. My tach is OEM digital yamaha multi function guage. I tried to find my motor at the Yamaha web site and had no luck. I guess I could just find someplace on the web that would have specs for my motor and check for the correct prop. <br />Side note: is Ring-free a good product?

 

[walleyehed]

Re: Prop for Yamaha 225

I can't honestly say good or bad...I prefer seafoam for decarb, and you can run it year-round.<br />You need to call a dealer or maybe someone has the link for aftermarket engine manuals...specs will be at hand that way.

 

[Dhadley]

Re: Prop for Yamaha 225

I dont understand why they said you need more pitch either. A single 225 on a 25' boat is asking a lot. You were at 5500 with a 16 and they "repitched" it to a 17. That should drop the rpm, not increase it, and therefore add stress to the motor. Going to a true 19 will really add stress.

 

[Perfidiajoe]

Re: Prop for Yamaha 225

Lot's of good info. here, but you need to know at what RPM your boat is running with what pitch prop, for the load you carry. You will have to get the WOT spec. to know where you should be, Try looking in repair manuals, the library is a good place. Better to own one though. You should prop to reach at or near max WOT RPM with a light to moderate load, the rest of the RPM range will follow correctly, (all providing the engine is sound). When you first described your boat/engine combo I thought 15-16 pitch before I read the the pitch of the prop you have, it's still my guess, or at least a good place to start. With the prop you have now, see how it runs, & at what RPM at WOT trimmed out, & go from there. Good Luck, Joe

 

[Perfidiajoe]

Re: Prop for Yamaha 225

One more thing, Remember, Going down in pitch will make the engine go up in RPM. About 150-200 Rpm's for each inch. And did your prop shop say anything about cup? good Luck, Joe

 

[jeuto]

Re: Prop for Yamaha 225

I spoke to my brother who gave me the low down...apparently it was at 15, the prop was changed by the shop to a 16 but they said it needs to be a 17. Sorry for the confusion. I will try to get some rpm number this week to let me know where I stand. With all the good information given so far I will have a good idea as to what the pitch should be and rpm as well. <br />Sorry for the wrong info above, I didn't mean to make you scratch your head and wonder what this crazy guy was talking about. I will let you guys know more about the test ride soon thank you for your comments.

 

[Dhadley]

Re: Prop for Yamaha 225

Regardless if it was a 15 or a 16 to start with, by adding "pitch" or bite they went the wrong way. You were at 5500 with whatever it was, which was too low, and now by adding pitch or bite it will be even less rpm. It was too strained before and now there is more strain on it. And they want you to add more strain. <br /><br />Think about it......