Proper prop for 90 Yamaha

[70smithy]

This post is in regards to a possible prop change on my 90 Yamaha.
Hopefully, answering the following criteria questions will help.

1) Performance issue you are trying to correct.
Need to increase RPMs to proper range and increase hole shot.
2) Current prop manufacturer, model, aluminum or stainless as a minimum.
Not sure of manufacturer. I believe it is steel but it is painted.
3) Current prop diameter and pitch (required).
13" diameter / 21 pitch
4) Wide open throttle RPM and speed with an average load (very helpful)
4300 rpm and 45mph with 4 people, twelve gallons of fuel, two batteries and a 30+qt. cooler
Rises to 4800 rpm and 48 mph with 2 people, 8 gallons of fuel and same batts/cooler.
5) Engine/drive make, model, year, and HP
1987 90 hp Yamaha (90 ETLJ)
6) Boat make model, year, length and weight
1974 Starcraft American bowrider (FRP), 16'-3", 870lbs dry (no motor or gear)

I just purchased this motor and it performs very well overall. However, it does not climb into the recommended RPM range (4800-5500 i was told. OK?) at WOT. I am also looking for more hole shot for water skiing without sacrificing too much top speed.

Also, I don't want to break the bank, IE: Aluminum. I've seen the brands out there (Solas, Michigan wheel, etc.) but don't want to pull the trigger without being more confident in my selection. Local Yamaha dealer can get props quickly but I didn't know if the OEM props are guaranteed to provide superior performance.

Thank you.

 

[BaileysBoat]

Re: Proper prop for 90 Yamaha

You probably have the Yamaha painted stainless steel. My Pro-50 of the same vintage came with one of those. I like the Yamaha aluminum props. You could try a 19P but you you might need to drop even lower with a heavy load.

http://www.yamaha-motor.com/outboard/powermatched/2010_props_oct_14_10/60~130, T50~F115.pdf

 

[Bamaman1]

Re: Proper prop for 90 Yamaha

You need to remove the propeller to find out the pitch and diameter--maybe on the back side of the prop. The chances are that any prop on a 90hp is a painted aluminum prop.

Your quoted speeds are awfully fast for a 90 hp 2 stroke. Have you doubled checked your speedometer vs. a GPS unit? Is your tachometer accurate?

I prefer factory branded props if the prices are reasonable. They seem to perform better.

See if there's a propeller shop in your area. Their expertise is free if you buy a prop from them. And, their prices are usually reasonable on an aluminum prop. They can easily suggest a prop that would be well suited for your needs.

 

[jestor68]

Re: Proper prop for 90 Yamaha

Each 2 inches of pitch will gain 300-400 rpm. Your motor's range is 4500-5500 rpm.

I use and recommend the Solas Rubex. A 19" pitch will get you up to about 5200 rpm with your "light" load.

I think your speedometer is off (on the optimistic side).

If you plan on pulling skiers, etc., a 17" would work well. It would put your rpm slightly over(5700) with a light load. An 18" pitch would be perfect, at 5500 rpm; if you can find one in aluminum. I see the prop section has one in SS.

 

[jestor68]

Re: Proper prop for 90 Yamaha

I prefer factory branded props if the prices are reasonable. They seem to perform better.

Guess who makes props for Yamaha ? And Honda ? And some others. Starts with "S".