1995 Evinrude 50hp problem running under load

[FishN-T]

Need suggestions, have done and tested all I know, boat ran fine until a few weeks ago, like I've read other's here with similar problems, starts fine, runs fine with muffs, put in the water, runs maybe half throttle speed. have rebuilt carbs, checked spark, compression great. I even rebuilt throttle control. I've seen posts that with similar problems some suggest possible coil problem, but starts and as I said, runs on hose too good for me to think that would be the problem. ANY suggestions appreciated.

 

[jbuote]

Real new here, but some thoughts to get started..

​You said compression is good. What's good? What was the compression?
​Also, you said you rebuilt the carbs. When you adjusted them after the rebuild, was it on the lake or on the hose? Did a link N Sync?
​It's possible to tune it to run great on the muffs, but lousy on the lake.

​Should really adjust mixture on the lake or minimum, in a barrel so you have back pressure on the exhaust.
​I'd, being new, start at the beginning again.. Check compression, spark with open air gap tester (sounds like you did those), then adjust on a lake or in barrel,
NOT of muffs.

​I'm sure some of the great folks here will be along shortly to offer more seasoned thoughts! lol

​For what it's worth from a relative newbie..

 

[racerone]

Ran fine and then it did not.------Did it quit at full throttle and cut to half power ??---Explain more in detail.-----It would run fine on a hose on one cylinder and that test means nothing.

 

[FishN-T]

OK, compression at 120-125, both cylinders. Both cylinders show good spark with tester. OK, how it runs, in water, starts, on low throttle does fine, but when I go to full throttle, it stops accelerating at like 1/3 throttle, runs, but fromm1/3 to 1/2 throttle forward it goes no faster.

​This started one day on the river, running fine one minute, then this. Then we did all the "maintenance" listed, put is water, the same. So, obviously not a carb adjustment, or a carb problem (doing same before and after carb rebuild).

​I am not close to being a mechanic, just a po boy that likes fishing and hopefully can fix this myself without the cost of a boat mechanic.

​Did have entire lower end rebuilt too, a nice $400 cost, and didn't affect anything, as I said, started one day on the river, obviously a problem I haven't addressed, but not sure I can do anything further.

 

[jbuote]

OK, how it runs, in water, starts, on low throttle does fine, but when I go to full throttle, it stops accelerating at like 1/3 throttle, runs, but fromm1/3 to 1/2 throttle forward it goes no faster.

​Do you mean the boat doesn't move any faster or the RPM's don't increase to full?

​If boat is not moving faster, and RPM's are proper, have you looked into the possibility of a spun prop hub?
​You said you had the lower rebuilt, but did that include a prop?

​That's about all the thoughts I have, so I'll leave it to the other folks here for any other thoughts... LOL..

 

[FishN-T]

No, RPM's never come up to where it should be. I move throttle forward and after about half throttle forward stays the same.

 

[jbuote]

Hmm.. Ok..
​Sounds like maybe throttle butterflies aren't opening or something...
​I really don't have the background on your year engine to go any further, so I'll definitely leave this one for the Pro's, such as racerone, to help with.
​I'm sure they'll be along shortly! LOL

​Sorry I couldn't be more helpful....

 

[boobie]

Do a cylinder drop test on it to make sure it's running on both cylinders.

 

[Stumpalump]

Your answers is probably above but water in the fuel makes them run like that.

 

[FishN-T]

I Cleaned tank out, all new fuel when I did all the rest Both cylinders firing. Took to the water today, same thing. Came home and pulled plugs, bottom was wet, gas, top maybe slightly wet also. Wiped them off and on muff running great, even idling. Guess going to be a trip to a marine mechanic, something this po boy don't need.

 

[boobie]

How do you know the cylinders are firing ??

 

[oldboat1]

In case you haven't done the test before, when running it in the driveway pull off plug boots one at a time (work gloves are a good idea). Expect some change when you pull off a boot -- change in rpms, stumbling or stalling. If you get no change, assume that plug is not firing.

Use of a timing gun to test spark is safe and effective on the water, but check on muffs first, if that's what you usually use. (may find, btw, that running with the l.u. deep in a water barrel will give problems -- back pressure, a little more similar to out on the lake).

 

[ondarvr]

You need to check for spark when it's acting up, what it does in the driveway doesn't mean much.

​Also check the timer base and make sure it's advancing all the way, along with the carbs opening all the way. These should be linked together and will move until both are moved to the stops.

 

[oldboat1]

I would initially check it in the driveway, though, even if it sounds fine. May find the issue before getting back out on the water.