78 model 85hp evinrude question

[gunlocators]

Ok I have a 24' Intec Marine Pontoon 88 model I put a 1978 model 85 HP evinrude off a 78 glastron bass boat to repower it. Just had the motor checked and carbs rebuilt and left the prop it had when it was on the 16' bass boat which is a 13 1/4x17 prop The issue today when I ran it out the motor sounded great however RPMs never got over 4400-4500 running wide open. My gps showed me running average of 19.2mph. I was told I need to be running wide open at around 5500rpms how can I acheive this is it possible its a prop issue.

If so I also have a 13 1/2 x 17 as best i can read on it its pretty wore also have a new 13 3/4x15 or do i have bigger issues than the prop here

 

[CaptainHook]

Re: 78 model 85hp evinrude question

As long as the motor is running properly it seems to me that you need to drop about 4 inches of pitch to get that thing runinning in the proper WOT range. So i would see if I could find a cheap prop or borrow one around a 13 3/4 X 13.

 

[CaptainHook]

Re: 78 model 85hp evinrude question

Sorry.....I read your post again, just to help determine I would throw the boat in the water for a quick run with the 15 pitch you have and see what happens. Should pick up some speed and rpms.

If it does (I would expect to see close to 5000 rpm) then maybe consider a 13 pitch to get you at 5500....

 

[gunlocators]

Re: 78 model 85hp evinrude question

I will try this this week end Thank you