1978 Evinrude 75 Top Cylinder Dry

[Prince2e]

Hopefully you guys can help me here! Ive been recently working on my Evinrude 75 doing some ignition testing. While pulling the plugs I noticed that there the top cylinder is dry. The plug doesnt even have a scent of gasoline on it. The piston had little droplet on it (not sure if this is water). The other two were normally wet and the pistons were also. I took the top carb off to inspect. It had fuel in the bowl and all the jets including the float were perfect. The reeds also looked good. They had some fuel sitting in them. What could be the issue here?

 

[boobie]

How's it run ??

 

[Prince2e]

It runs completely fine.

 

[racerone]

What does a compression test show ?

 

[Prince2e]

I haven’t done a compression test yet for it.

 

[racerone]

All 3 should show about 140 psi.

 

[Prince2e]

Let’s just say for example if that cylinder has low compression, what do you think it may be? What if it has good compression?

 

[racerone]

I think you should do the trouble shooting.----Or run to a shop.----Should be an easy fix here.

 

[Prince2e]

I just did a compression test. 149, 140, 140

 

[boobie]

Do a cylinder drop test on it.

 

[Prince2e]

Sorry for such a LATE reply. The cylinder turned out to be fine. Replaced Coils and power pack. Its runs much better but I have an issue where when I try to take off sometimes, it takes a few seconds before it getting the dedicated power to fully go and get on plane. From what ive been reading, im thinking i need to do a link and sync.

 

[Spartans]

You should try to Define sometimes. Does it do it enough to duplicate? I would check ignition again particularly when it occurs (if possible)

when you say getting the dedicated power are you seeing this issue appear under different weights in boat, etc? Note that 75 s of that era weren’t exactly known for quick hole shots so I would reconfirm your observations regarding power to plane

Lastly what is your control- the old power pilot?

 

[Prince2e]

When taking off sometimes which is usually most of the time, It will bog for a bit on throttle and then it will build its momentum and get up on plane. Once it’s on plane it’s completely fine. When I went out yesterday, I adjusted the idle screw and now it gets on plane just fine BUT since I adjusted that idle screw, I cannot move my warm level down on the control box since the idle screw is basically stopping the warm level from being adjusted lower. My RPMs are definitely too high but since it takes off much better, i’m assuming there is something off with the spark vs throttle plates opening too soon that causes the bogging before hand previously. Yes I assume I have the old pilot

 

[Spartans]

The issue with those outboards is that they were a slightly modified 70 which ran at a higher rpm (I think wot was 5800) but low end power really suffered. I heard that there were a lot of performance complaints when they were new so omc came out with a tsb to ventilate the prop so that it would slip slightly on take off raising the rpm which is what I am suspecting you are artificially doing with the idle speed.tinkering

I am not sure if ventilate is the proper term but hopefully I won’t get flamed and someone more experienced can chime in. If your low end is consistently poor I would look for the low hanging fruit ( prop mod, etc) before replacing components

you still should do a drop test and a spark gap test to make sure your ok on all three cylinders and that there is nothing loose corroded or weak

 

[racerone]

If fast idle lever won't come down on control box , you need to adjust the " black plastic thingy " on the cable at the motor.