1977 115 HP mercury OB Prop ?

[man1954]

i have a 1988 sea ray 18ft openbow with a 1977 115HP ser# 47 range, mercury outboard im trying to purchas a new prop but the the problem i have is i cant ID the prop i have now , i know its a 13 inch but the only #'s on the prop are PR 115577 and the word HIGAN si i cant tell what the pitch is , the motor runs great and right now my WOT is 27mph @ 5,500rpm i would think the wot speed would be more at that rpm but i dont really know , i mainley use the boat to run around with and do pull a skyer once in awhile and while pulling a skyer it seems to be slow in to pull them up and doesnt seem to have good top end. can someone id the prop i have and suggest a better prop for my use , ill carry about 18gal of fuel and sometimes 3 to 4 people
thanks

 

[usskydvr]

Re: 1977 115 HP mercury OB Prop ?

There is a PR 115, but that is a 14 x 11 for a 66-77 OMC sterndrive. It
could be a PR 157 (and they just put each number twice) which was a
13 3/4 x 15 Mercury outboard prop. This seems more likely. I believe the suggested max RPM for you '77 115 was only 5300 (the 150 was 5800)
so you are running a bit high and could probably switch to a 17 pitch and still keep your max RPM up. Those early inlines do not like to be lugged, but need to rev freely.

 

[man1954]

Re: 1977 115 HP mercury OB Prop ?

thanks so much for the info i believe your right, from center of the prop shaft i mearsure 6 3/4 '' to the outside of the blade ill try the 17 '' i think it will work much better.
regards