1978 85hp

R

rwcrazy

Cadet
Joined
Aug 18, 2006
Messages
16
I have an issue that it will not plane off.
Unless I have someone sit on the front, not an open bow, and weigh the front down, it will not palne off?
Do I have the wrong prop on the motor?

I have a 85 hp evinrude 1978 motor, it is a 15' glastron speed boat, any help would be great
Thanks
 
W

Walker

Captain
Joined
Jun 15, 2002
Messages
3,085
Re: 1978 85hp

Could be the prop, could be the angle and depth of the motor set-up. Could be a sick motor, could be a waterlogged hull.
 
jtexas

jtexas

Fleet Admiral
Joined
Oct 13, 2003
Messages
8,646
Re: 1978 85hp

Have a tachometer? What RPM's are you getting to at WOT, when it finally gets on plane? And/or what's your top speed, if known?

That motor should plane that boat pretty quickly. But the motor's got to be in good health. For a quick check-up, do a compression test and spark test.
 
E

ezeke

Supreme Mariner
Joined
Sep 19, 2003
Messages
12,532
Re: 1978 85hp

Which position do you have the thrust rod in? You might try moving it to position closest to the transom, then experiment from there.

When moving to plane, don't try to trim, just let the boat and motor tell you if you should set the rod further out.

Look down the keel to assure that it is straight and not bowed upward along the line towards the stern.
 
R

rwcrazy

Cadet
Joined
Aug 18, 2006
Messages
16
Re: 1978 85hp

I know I moved the pin in a couple different places, away and closer to the hull, when it was farther away it wouldnt go fast at all. maybe 15

No tach on the boat top speed anywheres from 30-38 depending on if im pulling someone or not.

once i put it in gear and give it gas, the motor automatically drop to the pin, (rod) and I cannot move the trim until I get up to speed

Looks like the prop says 13 3/4 X 15
 
cougar1985

cougar1985

Lieutenant Junior Grade
Joined
Oct 7, 2005
Messages
1,023
Re: 1978 85hp

15p prop would be no good for a speedboat. i have a 1300lb. tri-hull with the 90 rude and use a 17p which for mine is perfect.you relly do need a tac. it will save you lots of problems.assuming your motor is healthy and the boat is ok,can you borrow any props to try? id try a 17p and a 19p. but a tac is a must to see whats going on and to help get you in the proper operating range.according to my manual wot is 5000 rpm. l77jc4 plugs gapped at .030. hope this helps.
 
jtexas

jtexas

Fleet Admiral
Joined
Oct 13, 2003
Messages
8,646
Re: 1978 85hp

Larger pitched prop will have the opposite effect of what you're looking for...it might improve top speed but hole shot will suffer.

Risky changing pitch without knowing your RPM's...too high of pitch and you might be lugging the motor, too low and you risk overreving. A tach is essential for re-propping. See http://www.tinytach.com for a cheap digital tach.
 
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