Manual Jackplate Setting

[Probass1440]

Howdy ya'll,

        I have a questiong about the settings of my jackplate. On my 91 GT183 I have a 95 Yam ProV 6cyl 2stroke direct
injection 150. The prop that is on it now is a 25. I was hoping to find out if anyone could tell me what I can set my jackplate at to recieve optimal performance? The Jackplate does still have all the numbers on the sides for setting it. I'd appreciate it if you folks can help me or lead me to someone or a site that can help thanks a million.


                                                                                     ~Phil

[Ron Fogelson]

Well you need to find your MAX RPM's you can turn.  Then raise your motor up a 1/2 inch at a time tiesting your hole shot time and top end speed and keep raising until you lose speed or water pressure and then lower it about 1/4 inch and you should be set with that prop.  Each boat, motor and prop are going to be different so time on the water playing with it it the best way to dial it in.

Real Deal should be along before long and if you have your current prop to pad settings post them and he may know off hand the best hight to start with.

Good luck and let us know what you find.

[Probass1440]

my propshaft is sittin about 4,1/2 inches below the pad

[WRBass]

If you have a 10" diameter prop the nominal setting would 5" inches below the pad. Your water pickup ports may start to suck air when the highest port is above the water line at speed. Measure the top port hole down from the cavitation plate and don't go any higher without plugging the hole. Sounds like you are near the correct setting as is, try to go up 1/4" more and see how the boat handles the change.
WRB