94 gulfstream prop question

[ErieRik232]

My 94 gulfstream has twins yamaha 150 saltwater series 2 stroke.Only getting 4800rpm at wot.Acceptable range is 45-5500,so I am at low end of that.I have Michigan Rapture 14.25 x 17 stainless props.Was told these have extreme cupping and they usually pull more rpms than a regular SS prop of same size.I would like to see what other grady owners with twins have for prop size to make sure I am in ball park.I just bought the boat this spring and really love it,great boat.Would like to get her close to midrange to upper range of recomended wot....thanks

 

[Harpoon]

It sure seems like you should be spinning 5500 or so at wide open throttle. I have a gulfstrem 23 with a single. I connected with propgods.com and he set me up with a prop that is unbelievable. I'd recommend looking him up.

 

[DennisG01]

I don't have experience with those props, but it seems like a lot of RPM's to pull? But as you said, see what others with similar setups are running.

A couple variables...
-- Are the tabs retracting fully?
-- Are you trimming up properly?
-- Is the bottom clean?
-- Are the props in good condition?
-- Fuel quality?

 

[NautiBuoys]

On my Gulfstream w/bracket, I'm spinning 13 3/4 x 17" CR Yamaha props (Yamaha 150's) and hitting 5500rpm right on the nose.

 

[ErieRik232]

I raised my motors to 2nd hole,they were all the way down in first hole.I went up to 5000 rpm and 42-43mph.Still have room to go up as water still going over cavitation plate at cruise speed.What hole you gulfstream owners with dual motors and braket have your motors?I think I'm gonna try to go up maybe 1 more hole....thanks for the help

 

[Harpoon]

On my GS with a single, I thought my engine was running too low. Changed the prop, less pitch more diameter (per propgods) and the motor is no longer running deep. The stern is a little higher at cruise with the new prop. :wow