Hello all, I am currently running an 2004150hp Optimax on my 1850 SportFish(Crestliner).It has a 19 degree aluminum prop. I am gettingaround mid 40mph with a 5200rpm wide open.There is quite a bit of cavitation with this set-up when doing any turns. I end up having tothrottle back and reduce the turn. This is veryfrustrating when one is trying to do any kindof tubing. The Mercury site suggests a 21degree set-up, but my dealer is saying itdoesn't work?? Another suggestion was that myaluminum prop is flexing under load in the turnsand to go to a stainless prop. What are therest of the OptiMax people using?? My boatis 18.5 feet and approx 2300 lbs. Is a 17degree to small?? I would also think that5200 rpms w.o.t is a little low as well sincethe OptiMax is listed as 5250-5750 max rpms??
You might try an Alpha 4-blade aluminum 18" if you boat in shallow waters. Otherwise stainless props with 4 or 5 blades can actually run with some of the prop out of water and stay connected to the water in more adverse conditions or tight cornering. I mention the Alpha prop because the gearcase suffers less if you hit bottom if you're using an aluminum or even a plastic prop.
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Hey Tumble weed,Sounds like we're in the same boat! Pardon the pun.I've got a 2001 150hp opti on a 19.5 Fisher. Your setup is fairly close to mine. I'm 19.5 ft and about 2400lbs. I also get around 43mph GPS at around 5200rpm wot. Mine came with a 21pitch aluminum prop and it was a dog. 4800rpm was about all I could do but with a little better top end speed.I have played with a bunch of different 19p props with very little success. I too was told to try a 17P to see what happens. I actually ended up buying a 19p tempest plus this year as I thought it performed pretty good last year when tested but after putting the new one on this year it isn't performing the same. I tried a laser 2 and it is much better and gets those rpm's up to about 5400.The only other option is to try raising the motor up one hole to see if there is any improvement. I still haven't done that yet as I want to try a few 17P props to see what it does for performance.I won't be able to test anymoe props for about another 2 weeks but I can keep you posted if you like.
Is your motor mounted at the right height, and are you lowering the trim as you corner??And you are right, you want it to run at the upper end of the RPM range at WOT. I would try a 17 pitch and see what that does. The dealer should swap it out for free as it should have been set up right to begin with. Good luck.
Good question about the height. There is room todrop the motor down one notch?? The problemin the corners is felt at a fully loweredtrim. In looking at some other OptiMax motoredboats, I haven't seen ANY 17 degree set-ups out there. I had a closed throttle strike to the 19degree prop I had, so I am going to get to thebottom of the issue before replacing it withanother 19 degree aluminum again.