Need prop advice

[alamosaddles]

Ok, boat details..

Total weight of boat, rider, fuel and gear, on the water 1650 Now corrected to 1722 to adjust for the heavier 150 hp
Boat type Sea boss 19ft bay
Motor Johnson 2003 150hp
Manufacturer WOT RPM is to be 5500+/-
Motor runs perfect, no issues. Has less than 30 hours. I purchased this new in 2004.

Propellers tested
QL 3 blade aluminum, 14.8 x 17p
Piranha 3 blade composite 14 x 19p
Piranha 3 blade composite 14 x 21p

The aluminum blade prop I cannot return, so I am stuck with it.

The Piranha prop, I can return and exchange blades, so I am looking for the guidance of boating professionals in picking the better two sets of blades to exchange for. The boat is used primarily for watersports, pulling tubes etc., to include flying tubes like the Manta Ray.

As you can see from the tests I did today, I could not hit the Manufacturer WOT RPM number with any of the props. Suggestions on what to exchange for with the Piranha? Thanks so much.

 

[steelespike]

Re: Need prop advice

I think you may have left out the weight of the motor.
From my limited experience I think you should be able to make more rpm with the 17" aluminum.Have you optimized your setup? Starting with the antivent plate even with the bottom raise the motor a hole at a time to a point just before venting becomes a problem.You may pick up some rpm and speed.
2-3 mph under ideal conditions.Is the motor in good condition well tuned
throttle opening all the way?

 

[alamosaddles]

Re: Need prop advice

I think you may have left out the weight of the motor.
From my limited experience I think you should be able to make more rpm with the 17" aluminum.Have you optimized your setup? Starting with the antivent plate even with the bottom raise the motor a hole at a time to a point just before venting becomes a problem.You may pick up some rpm and speed.
2-3 mph under ideal conditions.Is the motor in good condition well tuned
throttle opening all the way?

Actually the weight of the motor was already included in the totals, but it was wrong, as I only tallied it with the 90hp that it comes with from factory. With the 150, it tacks on an additional 72 pounds, so I've corrected the numbers in the original post now. As to your questions.

The motor runs like the day it was new, perfect, no issues at all. Cav plate is set at the correct height etc. I prefer to optimize at this point just with prop adjustment. In the next few weeks, I have someone trading me, and installing for me a Stainless Marine bracket with swim platform in exchange for some new weapons, so I know that will again change the dynamics of the boat. At that point, he will likely pull my motor up a bit higher since the lower unit will be an additional 32 inches further back from the transom, running in clean water vs. all the turbulence of being close to the transom.

 

[erlindbl]

Re: Need prop advice

My suggestion would be to get the engine height straightened out before making a final decision on the propeller. I have a 150 HP E-tec on a 18 foot Glastron. It came set up too low. By raising the engine two holes I gained over 200 RPM. If you are planning on going to a stainless steel prop you can raise the engine a little higher than you can with an aluminum because they tend to bite the water better and have less of an issue with ventilation.

As far as the pitch of your prop, the 19P are too big. You are way below your recommended RPMS and that means your engine is lugging throughout the RPM range. The 17P is getting you close. If you went with a Stainless 17P and raised your engine some, I would think you would be right where you want to be. In addition, if you are mainly using your boat for water sports, the hole shot and pulling power will probably be more important to you than the top end anyway.

My advice, go with a stainless 17P and keep the aluminum as a back up. If you want to stay with the Piranah go with the 17P.