Wot RPM 115hp merc

[Crazy]

Got a 78 115 merc on a 18 foot fiberglass boat , had her out for the first time yesterday seen 5000 RPM @ 36.2MPH on GPS . It has a 19P prop on and man trim set @ # 4 , I just put the SeaRay wing thing on the motor ... and all I can say is WOW ! So what do you guys think ... is 5000RPM good for the old girl ? Or can I get more out of her ?

 

[Laddies]

Re: Wot RPM 115hp merc

I think that the 115 of that vintage were 5000 to 5400 RPM. in a average load condition, I use to run my 115 at 5800 with 2 people in the boat

 

[jimmbo]

Re: Wot RPM 115hp merc

5000 - 5500 was the range merc speced

 

[2cycle]

Re: Wot RPM 115hp merc

I would keep a 17 P on hand so you can be in the upper end of the RPM range under normal loads and in the range when you're loaded down. Prop it to make 5500 under normal conditions so it doesn't lug. Make sure your max spark advance is set @ no more than 21 degrees BTDC to avoid detonation issues. <br /><br />What vintage is your boat? I have a '73 18 ft. Glastron and a '75 1500 with a 17 prop that hits about 36 MPH. Yours must be lighter or have less drag.

 

[Crazy]

Re: Wot RPM 115hp merc

My boat is a Formula Firebird 18 foot 1978 it has a 7.6 foot beam and a deep V hull

 

[2cycle]

Re: Wot RPM 115hp merc

Originally posted by Crazy:<br /> My boat is a Formula Firebird 18 foot 1978 it has a 7.6 foot beam and a deep V hull

Mine is a tri-hull which must slow it down. Did Pontiac hijack the name?