81 merc 115 mariner rpms?

[PINIT]

Hey guys, i have a 1981 merc mariner 115 on my 65 Starcraft Jupiter and im wondering what kind of rpms i should be seeing from this thing. right now im at 4600 and about 35 mph. i have did research on this motor and 35mph is nothing, from what ive read this thing should be flying on this light boat. correct? Cheers..

 

[bktheking]

Re: 81 merc 115 mariner rpms?

5200-5500, (they will go as high a 6 grand but I wouldn't run it there long) is what it should do, at 4600 it's lugging, what prop is on it? What pitch and ss or aluminum? Aren't they rated for 85hp max????

 

[PINIT]

Re: 81 merc 115 mariner rpms?

5200-5500, (they will go as high a 6 grand but I wouldn't run it there long) is what it should do, at 4600 it's lugging, what prop is on it? What pitch and ss or aluminum? Aren't they rated for 85hp max????

i will check the pitch tomorrow, i dont remember. 14 comes to mind but idk if that sounds right to you guys?, and its aluminum 18 foot. not sure what HP rating. so to get 5200-5500 i would need a higher number in pitch prop?

 

[bktheking]

Re: 81 merc 115 mariner rpms?

Not knowing for sure, call michigan wheel and tell them you situation, they will recommend one.

 

[PINIT]

Re: 81 merc 115 mariner rpms?

Ok thanks, i know are the carbs are in sync and i checked to make sure they where wide open with the throttle at WOT and they are, so it would almost have to be the prop? it doesn't get out of the hole very fast and plains out quick. i know i need to rebuild the fuel pump cause it surges a bit wide open and i have to pump the bulb to get it to stop.