1980 Evinrude 115hp slow warm-up

Hi everyone, I purchased my first boat this past spring and have been having (what I believe to be) minor problems with the 1980 Evinrude 115hp engine warming up. I have tried searching the forums and google, but have not found any useful ideas, so I come to you all for assistance!

The engine starts up and idles well, but does not run properly for the first 15 minutes or so of use for the day. After allowing to idle for about 5 minutes at the dock, I leave the dock and idle along for a few more minutes minutes to ensure it is warmed up. Once warm, I increase throttle to around 3/4 throttle, but it does not throttle up properly and will cruise along slowly and occasionally spurt forward and then lose power again until, after about 10 or 15 minutes, it eventually gets up and goes and runs beautifully for the rest of the day! The boat can be shut off for an hour or 2, then will run without this problem; but if left for many hours, or overnight, I will have to go through the long process of warming the engine back up. The problem seems to last longer when the boat is left longer, and it seems to be getting worse with time.

Any ideas/suggestions would be a huge help!

Thanks everyone and safe boating!

Re: 1980 Evinrude 115hp slow warm-up

Have you checked the spark when it is cold to make sure it is firing on all cylinders?
Are the plugs in good shape, correct ones and gapped properly?

Re: 1980 Evinrude 115hp slow warm-up

I have just been using the (new at the time) plugs that came with the boat.. Would a spark problem change once engine is warmed up? Once it goes, it goes!

Re: 1980 Evinrude 115hp slow warm-up

You could have a plug or coil that woun't fire when cold.
Double check and make sure you have the correct plugs in the engine and they are gapped properly.
If the plugs are ok, check the spark when cold, needs to jump a 7/16" air gap and be bright blue.

Re: 1980 Evinrude 115hp slow warm-up

Thank you for your input, Daviet.. I will have a look at my sparks in the next few days to determine if this is a contributing factor. Somebody mentioned last night that it could possibly be a thermostat issue -- does this sound accurate? Would a broken thermostat cause the engine to operate too cold initially and cause the problems I described?

Re: 1980 Evinrude 115hp slow warm-up

You are probably priming the fuel hose bulb each time you cold-start the engine. That's normal. Usually that will fill the fuel hose from the tank to the carbs. However, it almost sounds like it is running out of fuel during the cold startups. Any chance the fuel is draining back into the tank after it is shut off-and it takes a few minutes to refill the fuel hose? Are you operating from a built-in tank? Does that tank have an anti-siphon valve? Any visible fuel leaks? What happens if you have someone constantly prime the fuel hose bulb when the engine is cold and it's running poorly?

Re: 1980 Evinrude 115hp slow warm-up

Hi emdsapmgr, I do have to prime the fuel hose bulb every time I cold start. After sitting for a day or two, I sometimes have to prime for quite a while until the fuel gets to the engine, but haven't noticed the problem when I only stop for shorter periods of time (20 - 30 mins). I am operating from a built-in tank, but I do not know if there is an anti-siphon valve (fairly new-to-me boat). The only thing I've noticed that could resemble a 'fuel leak', would be where the fuel hose attaches to the engine - sometimes it will not seat properly and when I prime, some drips of fuel will seep out -- I have blamed this on the fuel line emptying after a day or two, but did not think it would have any affect on cold performance as I assumed this would cause consistent problems, not just problems while cold. I have never tried pumping the primer bulb while the engine is cold -- I will definitely try that tomorrow!

Re: 1980 Evinrude 115hp slow warm-up

If you have a fuel leak on any fuel hose, not only does the fuel leak out, but worse-air will leak in. If you get air sucked into any fuel line, the engine won't run well. It may even run lean (starve for fuel) and that's really bad for an 2 stroke engine. Those fuel hoses do leak where they attach to the cowling. Personally, I'm not a fan of that type of connection. My recommendation is to bypass that connection altogether. Remove the hose barb that is screwed into the lower cowling. That leaves a hole in the lower cowling. Remove the engine fuel hose connector and thread the fuel hose end through the hole, circle it around under the cowling and clamp it direct to the hose barb on the fuel pump. (make sure you don't kink that hose when you bend it!) You will forever eliminate any fuel/air leaks that way.