16' bass boat 1978 evinrude 115 over reving

[stanfordky]

Well I bought the boat and used to run good but now when trying to get on to plane it does fine most of the time but then after getting onto plane rpms go over 7000. Prop slips and will never catch. I have 4 diffrent props and all of them have the same result. I first notice it with the 13x 19. I have also tried the 13 1/2 x 19 not as bad but still slips it too. It has hot installed on the boat. I hooked up the factory controls and still the same. Its got me scratching my head and I dont want to burn up the powerhead. I thought it was the prop spun but changing it didnt help. Any suggestions please.

 

[boobie]

Re: 16' bass boat 1978 evinrude 115 over reving

Do you have a restriction on the bottom of the boat causing the prop to ventilate ??

 

[stanfordky]

Re: 16' bass boat 1978 evinrude 115 over reving

No theres nothing restricting. Bottom of boat is clean. I dont understand I bought a new tach aswell thinking that the tach may be off. When the boat jumps onto plane the rpms peg out and I let off of the hot foot and ease back into it seems to hook up and then pegs back out when giving more throttle.

 

[doug1257]

Re: 16' bass boat 1978 evinrude 115 over reving

Just got into OMC always ran mercs. But if you've tried 4 props it's not the prop. Something in the drive system. Lower unit, drive shaft splines ect

 

[bonzoscott]

Re: 16' bass boat 1978 evinrude 115 over reving

Try The "Marking the hub" trick to check for spun prop. are any of them new?

 

[Bob_VT]

Re: 16' bass boat 1978 evinrude 115 over reving

Sounds like the symptoms of an incorrect shaft length. I have seen a few people swap motors and not pay attention to shaft length.

Verify the position of the anti-ventilation/cavitation plate with the keel of the hull.

 

[dwco5051]

Re: 16' bass boat 1978 evinrude 115 over reving

Does this motor have power trim/tilt? If so is the motor able to trim all the way down? Was the original prop you were running cupped and the other ones not cupped? Have you added anything that could change the weight distribution or any transducer? (extra batteries, different trolling motor, etc.) A picture of the stern showing the the location of the motor would help. The boat is 35 years old and I would be suspicious of possible water logged flotation that may have caused stringers to become weakened and a possible hook in the hull.

EDIT: I reread your post and it seems that it over revs after getting on plane. The first two question most likely don't apply.

 

[emdsapmgr]

Re: 16' bass boat 1978 evinrude 115 over reving

When the boat used to run "good" was it turning a stainless steel prop? They get a lot more bite when running in high transom mounting situations.

 

[stanfordky]

Re: 16' bass boat 1978 evinrude 115 over reving

When I get home tonight I will get some pics of the boat and motor. The boat is a 1991 and the motor is a 1978 so yes it has been changed.