[Evinrude 1977 70hp - Throttle Issues]

I took the coil out but couldnt complete it cause i was worried i would damage the wiring. From the coil side the wiring seems to be fixed into the coil, ie, there is no connector to undue. From the other end the cable goes into the powerpack and this also seems to be hard wired inside the pack. There are some bolts to undue which i think is the power pack, but i didnt touch it as it looks like it has a gasket under it. There other wire goes into some distribution board.

[Evinrude 1977 70hp - Throttle Issues]

One thing i did notice is that the spark coming out the spark plug lead to the number 1 cylinder was very minimal when the engine was hot. When the outboard was cold all cylinders were firing fine. I'm no expert but to me it looked like only a really tiny spark was coming out when the outboard was hot. In a car engine you can actually hear the spark ticking. So i will check the coils and leads today and see how it goes. Hopefully they are not difficult to swap around for testing. Thanks.

[Evinrude 1977 70hp - Throttle Issues]

Took the boat out this afternoon with a marine mechanic.

Prior to going out, compression check was done on the 3 cylinders with apparently good compression. Outboard was rated as good condition for its age. Pumps out water fine and sounds pretty normal.

Took off and gradually gave it full throttle. Absolutely flew onto the plane with ease. About 10 mins later we slowed down to turn back. This is when we lost power again. Boat would not pick up speed. Took us about 20 minutes to back to the ramp. Docked at the wharf where the mechanic started testing some things. The number 1 cylinder was not firing when the leads were taken out one at a time. Spark was coming out of lead, so electrical seemed fine. Cylinder 2 & 3 were fine.

Next was to put new spark plugs. Started outboard, and all cylinders were firing cause the outboard had cooled down. Went out again. but same thing happened again.

Tested compression again later and was fine. Even mechanic was dumb founded as he could not pin point the exact problem. Either piston is no good, cracked block or anything. Could be fuel problems to the number 1 cylinder when it gets to operating temperature.. Outboard was not overheating either. To start pulling it apart is a timely and costly thing and could end up costing more than whats its worth.

I am stuck and have no idea what to do. Sell boat as is, fix outboard or spend money on another one.

Has anyone had these sort of symptons b4 and can share with me?

[Evinrude 1977 70hp - Throttle Issues]

Thank you all for the great tips. Will be taking the boat out for a spin with a recommended marine mechanic tomorrow. Will keep everyone informed of status. I really have learned a lot from everyone. Many thanks to all.

[Evinrude 1977 70hp - Throttle Issues]

I have put it in with a marine mechanic and he seems to think it is a breather problem. Will get it fully checked just in case it is something else. Will get a full service done as well.

[Evinrude 1977 70hp - Throttle Issues]

I have been told that it maybe a tank breather problem. As the plastic tank i have does not seem to have a breather. If it is a breather issue, would it affect the throttle and power all the time or only when it warms up?

[Evinrude 1977 70hp - Throttle Issues]

Posted - 06 Feb 2007 : 11:25:54 AM

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Hi All,

I bought a Nautiglass Deep V Cuddy Cab over the weekend with a Evinrude 1977 70HP outboard. Its a good boat around 1987, and the outboard is an oldie 1977 model. It seems to be in good nick.

Took it out yesterday, and is stared first go. Let it idle for 5 mins to warm up and took it out onto the Georges River. It flew and got onto the plane quite quickly and comfortablly. After a few minutes i slowed down to turn back, it would not pick up speed. The throttle was put to the extreme, but it barely went more then 10km and hour. Went back to shore, and checked fuel lines which seemed ok. Mixture was fine 50 / 1 . Added a bit more outboard oil to tank and went back out. Again it flew, but a few mins later it slowed down again. Rang the owner who i bout it off and he said he has not had any issues with it when he last took it out a week ago.

Can anyone please assist me with this issue. Maybe you have experience in this. The outboard sounded ok, pumped water fine. Looks good under the cover, no leak, no heat staining marks., etc. Thank you.