'75 Evinrude 85 hp hesitation in acceleration

[Lucky13ESP]

This engine is driving me crazy. Runs fine in the driveway with the flushing muffs on but when I get it to the lake, everything falls apart. Has a rough time idling in the water (idle speed is turned all the way up). When I can finally get the warm up lever down enough to get it into geer, it hesitates while accelerating. Either one of two things happen<br /><br />1) It revs up and dies if I just accelerate up to full.<br />2) If I work it slowly up, it sputters around 1/4 throttle and after sitting there a while, kicks it in a little and then I can accelerate to full.<br /><br />She runs fine once you get her open but the sputtering makes watersports a challenge. Again, it works fine with the muffs on. The only thing I can think of is in the drive the prop doesn't have to do any work. Plugs are clean, gas is 50:1, 87 octane (no ethanol), TC W3 oil, and the fuel filter is clean. Any advice is greatly appreciated. Thanks

 

[Walker]

Re: '75 Evinrude 85 hp hesitation in acceleration

I know this sounds generic, but maybe its time for a total carburator cleaning/overhaul and a tune-up.

 

[bubbakat]

Re: '75 Evinrude 85 hp hesitation in acceleration

Sounds like a fuel problem. Take the carbs off and clean and rebuild them.<br />Have you had the motor long and also do a compression check and see what we have and report back.<br />Has this been a problem for awhile or is it just starting to be a problem.<br />Check fuel tank and make sure it is vented.<br />Get someone to pump the primmer bulb to see if that helps.

 

[Bass Runner]

Re: '75 Evinrude 85 hp hesitation in acceleration

Check the advance and make sure the linkage is moving free, if it is hanging you are trying to accellerate with the timing retarded.

 

[OBJ]

Re: '75 Evinrude 85 hp hesitation in acceleration

Hi Lucky....reason it runs so well in the driveway is because there is no backpressure against the cylinders that is created by being in the water. So, the engine dosen't have to work as hard.<br /><br />As posted above, a good going over won't hurt. Take compression readings on each cylinder. They should be within 10 to 15% of each other. Write it down for future reference.<br /><br />Make sure the spark is good. Each spark should jump a 7/16" gap with a hot thinck blue white spark. <br /><br />If you don't know when the carbs have been overhauled and cleaned, nows the time to do it.<br /><br />If you want go the whole route, when was the last time the water pump impeller was serviced?<br /><br />And as always....get a service manual if you don't have one. Makes the work so much easier.<br /><br />Keep us posted and don't hesitate to ask questions.....Thanks.

 

[Lucky13ESP]

Re: '75 Evinrude 85 hp hesitation in acceleration

Thanks so much for all the advice. This guarentees me something to do this holiday weekend. I'll get back with you soon. Thanks again