1976 Evinrude 85

[fireman_103]

I just put a 1976 evinrude 85 on my boat which is a 1976 skeeter and it originally was equipped with a evinrude 115 and went across the water nicely. I put her in the lake yesterday and only got 4200 rpm out of it. The prop is the stock prop. Compression is 95 on all four, I have rebuilt the carbs, new plugs. The boat came out of the hole pretty slow and at full trim would only get to 4200 rpm. Should'nt I get about 5600 rpm. I need some hints on what to do.

 

[tashasdaddy]

Re: 1976 Evinrude 85

decarb the engine, and check compression with a different guage, 95 is a little low, but could be guage, but they are equal at 95 is a plus. will probably have to reprop, prop forum, is your engine height at the optimum. 76 skeeter is a heavy boat, had one years ago.

 

[WillyBWright]

Re: 1976 Evinrude 85

No such thing as a stock prop on anything bigger than a 35. Motors larger than that are propped according to what they're hung on. You need to repitch down. But first, make sure the motor is in good running condition. Maybe it's not firing on all four despite compression, rebuilt carbs and new sparkplugs. Are all four plugs getting spark? Are your throttle butterflies opening fully? Is your timing advancing?

 

[fireman_103]

Re: 1976 Evinrude 85

I have checked the spark. I actually changed the stator base and all four have a strong blue spark. The carbs are opening up fully and the timing is advancing. I think I will have to check the prop. Will the prop off of my 115 have to much pitch for the 85 to work properly. Or is it possible that the foot off the 115 will have better performance it looks like the gear case is much fatter on the 115.

 

[ezeke]

Re: 1976 Evinrude 85

The gear case and gear ratio should be the same on the 76 85HP and 77 115HP. The engines however are not. The 85 has 3-3/8 bore compared to 3-1/2 on the 115. Displacement on the 85 is 92.6, compared to 99.6 on the 115.

I absolutely cannot understand what genius put propellers on a different forum. The whole purpose of an outboard motor is to turn a prop. Without it, it is like a car without wheels. It is arguably the most important item in the whole setup and should not be neglected in this forum.