1969 55hp johnson problems

[59_seafair]

Ok so I just took my new boat out on the lake today to test it out. I have done all the checks on the motor(s) the past few weeks. I replaced the water pump assy. When we were out on the lake today the motor was running good for about 10 minutes or so and then it lost all power. When I put it in gear at about 1/2 throttle it will push the boat real slow, and at full throttle it dies. In neutral the motor will run wide open. I pulled the lower unit when I got it back to the house. Everything looks fine there, any one have the same problem or know a way to fix this?


Thanks it forum has so many great people. I am glad I found this one.

 

[Daviet]

Start off by checking the compression and spark, those engines will idle real well on two cylinders.
Oh, don't run more than 1500 - 2000 Rpm in neutral or you might have some more problems to worry about.

 

[59_seafair]

Re: 1969 55hp johnson problems

Yeah I just checked the compression all 3 are about 90. I also checked the T-stat to make sure that was opening at about 140 that checks good too.

 

[Daviet]

Re: 1969 55hp johnson problems

What about the spark?

 

[59_seafair]

Re: 1969 55hp johnson problems

good spark on all three

 

[Daviet]

Re: 1969 55hp johnson problems

Compression is 90 on all cylinders, not great but equil.
Spark good, will it jump a 7/16" gap and is bright blue?
All that leaves is fuel, try squirting some fuel mixture into each carb and see if it picks up.

 

[59_seafair]

Re: 1969 55hp johnson problems

Thanks for your help. I will try that in the morning.

 

[asthedeer]

Re: 1969 55hp johnson problems

I had a very similar problem with my 1979 evinrude 55 hp.

What happened was the connecting rod bearing blew apart in the #1 cylinder and I had to rebuild the engine. Which Iam currently doing.

To evalute take a plug out and look down the hole with a flash light or a compression test. Or to evaluate for sure take the head off and take a look.

Hopefully things will work better for you than for me

all the best

 

[59_seafair]

Re: 1969 55hp johnson problems

Ok so I pulled the head unit off and all cylinders are good (in fact a lot better then I thought they would). Could it be the carbs that are messing it all up?

 

[Daviet]

Re: 1969 55hp johnson problems

If the spark and compression are good, then the next step would be carb overhaul.
Why did you remove the cylinder head?

 

[59_seafair]

Re: 1969 55hp johnson problems

I just wanted to rule out the cylinders from being bad. I will do the carb rework today then

 

[Tim Frank]

Re: 1969 55hp johnson problems

I just wanted to rule out the cylinders from being bad. I will do the carb rework today then

The compression check pretty much did that. Did you use a new head gasket?

You should get a repair manual so that you are not chasing your tail.

The fact that it ran well before acting up would make me doubt that you actually have a carb problem.
Before rebuilding the carbs there are a few simple things to check that could give the symptoms you describe.

1) the fuel hose connector on the motor can be a problem. You can change the o-ring, but because of the constant connect/disconnect at the engine end, it can happen that the hose-end fitting actually wears to the point that it should be replaced.
Try a "known-good" tank and hose to rule this out.

2) second choice is the tank end connector.....same as above, but usually not as much wear there.

3) if the bulb is soft and pumping it up restores the performance, suspect a fuel pump issue.

 

[59_seafair]

Re: 1969 55hp johnson problems

Yes I used a new gasket for the heads. I will try to switch out the hose and connections today and try it again. I have two new hose assy on the boat so that will be an easy attempt.