Blue Wave 165T and Yamaha 90 2 Stroke

dewey.elsik

Recruit
Joined
Jul 3, 2013
Messages
5
I upgraded from a 50 to the 90. I have a Solas Prop that came with the motor but I really want a 4 blade stainless. Looks like a 13" diameter is what I have found to be recommended but have no help on pitch. I really want to get this right the first time. There has to be someone running my combination. I even called Blue Wave and they referred me to their GURU in East Texas who will not return phone calls.
 

SkiDad

Lieutenant Commander
Joined
Jul 18, 2010
Messages
1,518
you need to run the prop that is on and let the guys here know you RPM and your speed via a GPS. That's a prety light boat - i would think a 19p would be minimum but the info you give us will help us give a better recommendation.

But the concern is that you might be over powering your boat - i see 75 hp as the limit on one model and 90 on the Super T. and you might get yourself in trouble legally depending on state.
 

Texasmark

Supreme Mariner
Joined
Dec 20, 2005
Messages
14,544
The numbers mit mentioned are Wide Open Throttle numbers with your normal load, engine trimmed for best performance/mph. On a SS prop if cupped, say so as that could be the difference in an inch or so of additional pitch in considering your best guess.

Mark
 

steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
It sure could be easier with an identical setup;but in 12 years I think I've seen two or three such lucky coincidences.
All this testing for numbers is to see if your setup works and to see if your motor is healthy, evaluate the tachs accuracy
And to have a gps speed for accuracy.
Usually we have accurate results but it can't be done without some numbers.
 

dewey.elsik

Recruit
Joined
Jul 3, 2013
Messages
5
OK, no speed because my son dropped my phone in the water. Not a good day. The thing pulls strong but i have the motor too high. Cavitates too much on the turn. I am going to drop the motor when i get home. I have a Solas AL 13.25 X 17 prop on it right now. I can only get 4500 RPM. compressions are high on all cylinders and it pulls very strong. This may be too much prop. Next? I understand a 4 bladed prop will help on a tunnel.
What says you?
 
Last edited:

steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
You probably should have told us the boat is a tunnel. There have been thousands of builders over the years so
there are probably many of us that don't have a clue about the Blue Wave.
A 17" prop at only 4500 rpm I would suspect The tach first. May be you could borrow a GPS or cell with gps the accurate speed will help us tell better about the tach reading.
 

Texasmark

Supreme Mariner
Joined
Dec 20, 2005
Messages
14,544
I just googled your gear ratio and it replied 2:1. That helps (over a 2.33 like my 90 Merc) but as steel said, 4500 rpm with a 90 on a 17' tunnel which should run out really well due to flat hull and a 17P isn't much prop. You'd expect your rpms to be on the top side of the recommended rpm band. The 4 blade Stainless will help for a fast hole shot and better gripping, and it probably will have blade cupping which will help prevent your blowing out. I don't know how you could not expect some especially in a turn. Too much turbulence preceding the prop.

The big guns on here always said to get your setup right and then mess with the prop to get your rpms where they need to be. Lowering your engine will contribute to more drag and drop your rpms somewhat and you are already too low according to your numbers. I'm here and you are there, but I think your idea of getting another prop, since it is significantly different might be the first thing you do to cure some of your problems. The problem is determining the correct pitch and an accurate rpm number IS required for that.

HTH,
Mark
 
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