1970 Evinrude 6hp Fisherman - lacking power

[rtgambit]

Figured I would come to the best place to try to sort out my issue.

Problem is that the motor will start up and idle without too much worry, but lacks any top end power, and produces a lot of smoke. I've already done a carb rebuild kit and cleaned out the passages with compressed air. The float was replaced with a new plastic one, and made level with the rim of the bowl.

Plugs are brand new, as well as the wiring, coil, condensers and points. Compression shows roughly 110 psi on both cylinders with 3 pulls.

Gas is brand new, and mixed to the proper 50:1 ratio. Tank is clean with no rust. Gas line and bulb are brand new.

I replaced the gas line running from the pump to the carb with a clear one, just to make sure I wasn't picking anything up. I also replaced the other 3/16 line that runs near the pump (sorry, not exactly sure of the nature of this one, only that it was very cracked).

Some extra information: that second 3/16 line is showing a low pressure towards the high side, evidenced by a small amount of gas in the bottom area when running.

 

[1946Zephyr]

Re: 1970 Evinrude 6hp Fisherman - lacking power

What kind of boat is that motor running on? It sounds like the motor is in decent shape and compression is excellent.

 

[rtgambit]

Re: 1970 Evinrude 6hp Fisherman - lacking power

What kind of boat is that motor running on? It sounds like the motor is in decent shape and compression is excellent.

Oops, looks like I left that part out. This is the way it's acting in a barrel full of water.

It's normal duty is behind a 14' Starcraft aluminum (obviously same type of behaviour there).

 

[rtgambit]

Re: 1970 Evinrude 6hp Fisherman - lacking power

I'll add that I tried pulling the spark plug wires separately while in idle and in gear with the throttle wide open. Both plugs had the same effect - RPM dropped and the engine started sputtering.

 

[steelespike]

Re: 1970 Evinrude 6hp Fisherman - lacking power

The fuel pump may have a bad diaphram leaking gas into the crankase.
Is the lync and sync set right.Does it pick up the carb at the correct point
and does the stator advance as it should.
Are the points set at .020 on the highest point on the cam?

 

[tx1961whaler]

Re: 1970 Evinrude 6hp Fisherman - lacking power

The fuel pump may have a bad diaphram leaking gas into the crankcase.

^^^^
Unbolt the fuel pump from the block and squeeze the primer bulb. There should not be any gas squirting out the back of the pump.

 

[rtgambit]

Re: 1970 Evinrude 6hp Fisherman - lacking power

^^^^
Unbolt the fuel pump from the block and squeeze the primer bulb. There should not be any gas squirting out the back of the pump.

Just back in from the garage - the pump passes this test. It's absolutely bone dry where the pump connects to the body, and no gas squirts out when squeezing the bulb.

 

[rtgambit]

Re: 1970 Evinrude 6hp Fisherman - lacking power

The fuel pump may have a bad diaphram leaking gas into the crankase.
Is the lync and sync set right.Does it pick up the carb at the correct point
and does the stator advance as it should.
Are the points set at .020 on the highest point on the cam?

Going back out after lunch to check lync, sync and stator advance. Haven't been able to find my feeler gauge, so a trip into town might be necessary.

 

[rtgambit]

Re: 1970 Evinrude 6hp Fisherman - lacking power

Plugs are brand new, as well as the wiring, coil, condensers and points. Compression shows roughly 110 psi on both cylinders with 3 pulls.

Guess one should never assume anything. The plugs are brand new, but apparently someone never gapped them properly. The poor thing was trying to run with about a .25 gap. Opened em up to .40 and it seems much happier (happy enough to empty the water barrel when I tried WOT in forward). Time to test it on the boat!

Thanks for all the suggestions! I'll report back later tonight with the findings.

 

[rtgambit]

Re: 1970 Evinrude 6hp Fisherman - lacking power

Motor did a little better in the boat than before, but still not able to get full power from WOT. Picking up a feeler gauge set after work tonight, we'll see how things look under the flywheel.

 

[rtgambit]

Re: 1970 Evinrude 6hp Fisherman - lacking power

The fuel pump may have a bad diaphram leaking gas into the crankase.
Is the lync and sync set right.Does it pick up the carb at the correct point
and does the stator advance as it should.
Are the points set at .020 on the highest point on the cam?

Points were at .012, and slightly rough. Cleaned up with fine file and regapped to .020.
The sync was off between the cam and follower, so that was adjusted properly, too.

Now I just have to wait till Friday to test on the boat again!