Correct prop size for 115 Yammie 2s? (by whiteman)

[WillyBWright]

Post Subject: Correct prop size for 115 Yammie 2s? Posted: 3:51am Today
2001 Saltwater series 115 2s. The service engineer doing the annual looks at the 19" prop and says "who put that on? - it's too big - you should be using a 17" prop".

This guy seems to have done a really good job on the service and seems to know his stuff. He reckons a 17" will get the motor on the plane faster with a higher WOT rev count. It will simply work better in his words.

What the? The 19" prop came with the motor as new. No other service guy has made this observation.

Any of you guys (and gals) have an opinion on this subject?

 

[WillyBWright]

Re: Correct prop size for 115 Yammie 2s?

Re: Correct prop size for 115 Yammie 2s?

I took the liberty of reposting this here.

First, only motors that are packaged with a fuel tank have props installed by the factory...little ones. Bigger ones come without so dealers can determine the correct propeller for the package.

Second, the mechanic is probably making a moutain out of a molehill. 17 and 19 aren't so far apart. They're nextdoor neighbors in the pitch spectrum.

It all depends on how many RPMs your motor is turning at full throttle with an average load. If your tach shows about 5500 it's right. If you're a little short, say 5000, then a 17 may be more appropriate. (I wouldn't be afraid to twist that motor up to 6 grand)

Most boats are prepackaged these days. The boat factory supplies the prop that they have determined to be correct for that package. It may need one prop faster or slower depending on how the boat is actually used. Even if it wasn't a factory package, boat manufacturers have charts with various combinations that are usually within a prop size plus or minus.

It is ALWAYS a good idea to have two props. Your car has a spare, so should your boat. Most of the time I recommend two different pitches. One for speed, the other for pulling. Lower pitch gives quicker holeshot and slower top-end. Higher pitch gives slower holeshot and faster top-end.

 

[whiteman]

Re: Correct prop size for 115 Yammie 2s? (by whiteman)

Willie, thanks for moving the post. I didn't realise there was a prop section. And thanks for your explanation. The 19" prop works great but it does tend to want to back off the revs once it's pushed past 4800. Gets to 5400 in the current config which is 35 knots and steering is getting very light at that point.

As for a 2nd prop, in Australia, a 17" s/s prop costs from $A650. I have figured that if I damage the current prop to the point that it doesn't work, I've probably done a heap of damage to the drive shaft, etc, etc. I'd reckon a tow in would be called for.