1976 evinrude won't rev up

[johnny whaler]

I have a 1976 evinrude that's ben giving me problems. I had cleaned the carb, put in new plugs and finally it seemed ok. It ran great for 90 minutes High end, low end start stop etc. Then it started to run lousey again. Now I have it idling great and it will rev up but no where near top RPM. It's a real pig now. Spark is good and blue, compression is over 120 and equal. I did find the top plug fouled out and repaled it and it fouled it a couple of times. This seemed to stop now. The wire for the top coil was what looked to be a bad connection.

One thing I did notice is it runs MUCH better with the engine cover of than with it on. It will pretty much rev right up with the cover off and almost dies with it on. I haven't had it in the ocean with the covr of but it seems like it will run good with it off. his is driving me nuts. I'm ready to take out a loan and buy a new engine but I know this one is good and I'm just missing something.

I did find pain flakes in the engine compartment from the carb cleaner melting the paint. Alos the foam was horrible. Could this be the points? Or could it be the carb sucked in some foam or paint flakes? The paint was wet and bubbled. I sprayed the heck out of the carb. It's just strange that it runs better with the cover off. I also tried the slow speed (the only adjustment) at 1 turn, 1.5, 2, 2.5 and 3 turns. It doesn't get it any better.

Electrical or fuel??? I'm going nuts. Compression, spark and fuel and it will run. It runs but not good!:''(

 

[Joe Reeves]

Re: 1976 evinrude won't rev up

Running poorly only with the hood installed indicates that you have either a blocked air intake, or more likely a exhaust leak entering the powerhead area which would be drawn into the carburetor throat.

If there is no exhaust leakage anywhere, I'd suspect that the engine is located in such a manner that the normal exhaust fumes cannot be dispelled properly and is being drawn into the air intake, then into the carburetor.

 

[johnny whaler]

Re: 1976 evinrude won't rev up

This is all starting to make sense now. The engine is somewhat loud. Where do I look for the exhaust leak? I would think it escapes through the shaft where would it leak in the engine compartment?

It also makes sense, high speed it was probably drawing out the exhaust and when I slowed down it could only flow up. This is a long shaft on a 15" transome 1963 whaler. Could it be the engine is too low in the water?

Another Dumb question is where does the intake air flow from? The only opening I see in around the shift lever. There is a rubber gasket there which is pretty much roted away. I don't see any other opening anywhere that air would flow into the engine compartment with the cover one.

Thanks for your help so far!! I think we are getting somewhere. I'm tempted to take it for a ride with the engine cover off just to see.

 

[Joe Reeves]

Re: 1976 evinrude won't rev up

Some hoods have a opening for air but the main opening will usually be right under the carburetor.

You cannot use a 20" shaft engine on a15" transom.

The noise/exhaust source? I wouldn't have any idea unless I was inspecting the engine personally.

 

[johnny whaler]

Re: 1976 evinrude won't rev up

What is the implication on using the longer shaft on the short transom? Is it performance, safety or does it affect the engine? Could this be my problem all along? MAybe it ran good on plane because it was up higher out of the water? What are the ill effects of a long shaft on a short transom boat?

 

[johnny whaler]

Re: 1976 evinrude won't rev up

Joe ....one other question....There are the normal 2 exhaust ports on the rear of the engine that point aft. But I see 2 more ports about mid-shaft that point forward towards the transom. I have lost of exhaust and noise comi ng from these two holes. Great water spray from the aft 2 ports but mostly noisy and smokey exhaust from the 2 ports that point towards the transom. When I plug these with my fingers the exhaust blows out through the prop and sounds like a normal engine again! I think we are on to something here. The exhaust rom these two holes is traveling up through the intake (which I found below the carb) and probably 99% of my problems here.

Is exhaust supposed to flow from these other 2 ports?

 

[johnny whaler]

Re: 1976 evinrude won't rev up

As crazy as this sounds, I just took some Duct tape and put some over the two forward facing exhaust ports. I then started the engine. It runs like normal and actually sounded like it shoud sound. I have a new book on the engine but it doesn't show a break down or the exhaust. I am almost thinking this is the exhaust port for when you shift into reverse??? Maybe I'm wrong. I think this has ben the issue all along. These 2 ports are under water when the boat is in the water. Beofre I buy a jack plate I want to determine if this has ben the cause all along. The engine runs perfect with these holes pluged up but I don't think an Evinrude engineer put them there for me to epoxy over! Something isn't working right.

I apprecate the help. I had this thing at 2 different shops and they pretty much just start changing parts when I think it's ben an exhaust leak all along. Now just how to fix it.....

 

[johnny whaler]

Re: 1976 evinrude won't rev up

I can feel the drive shaft spinning through these two holes or ports that face forward. I am starting to believe these are supposed to have rubber grommets or something and are more of an inspection port or relief valve and I need to cover them up. Am I wrong in saying this? I think this has ben my issue all along.