temporary power loss

[cowboy_ed69]

I got a 1984 mercury 115hp outboard. I heve rebuilt and sinc the carbs, fuel pump, new fuel lines, ignition control boxes spark plugs and coils. The problem I am having is when I am slowly going through a no wake zone, after I get out of the zone and go back in wot my motor will come to about 2100-2200 rpm and hold there for about a minute or two the go on up to full power. It will not act up from the dock or after fishing, just when I'm am trolling or no wake. The problem will not replacate on land or in a water pit

 

[Chris1956]

Check the fuel pump. If the diaghram leaks a bit, it will "load" up a cylinder, causing low power after idling. After a while the spark plug starts firing again.

 

[cowboy_ed69]

I have rebuilt the fuel pump with new diaphrams, cause the old ones was cracked but it didn't help

 

[Chris1956]

OK, maybe the carb linkage or trigger linkage sticks? What do the spark plugs look like? Maybe water infiltration? Flooding carbs?

 

[cowboy_ed69]

New plugs, all the linkages move freely. It will not flood the carbs or get water inside. When it dose this, I have to pull throttle back to about half way where it would normally be at for that rpm. Slightly give more throttle until the rpm start coming up off about 2100-2200 rpm. Once it starts commingled up I can go back in to wot and it will not act up again until I have to go slow through a no wake zone or stump field

 

[Chris1956]

Maybe you have a exhaust leak into the cowling? That would starve the carbs of oxygen and can cause acceleration issues. Take off the wrap cowl and retest.

Other than that, I am at a loss for advice....

 

[cowboy_ed69]

I've had the crowl off while I was checking the timing movement as the rpms was going up, thinking it might be a timing issue. But the timing advance moves the way it suppose to. I was troubleshooting it on the lake when another mercury owner came by ask ask if everything was good. So I told him what it was doing and he mentioned that maybe it could be on one of the piston valves not closing off all the way or a piston ring not expanding as the cylinder warms up and allowing exhaust pressure to build up in the crank case. I'm wondering if there is a pipe plug on the case that would allow my to install an electric valve so I could flip a switch and blowoff the pressure. I looked but didn't see one just wondering if the is one hidden out of sight or would I be able to make and tap a hole in the case. If so where would be a good spot for it

 

[Danny C]

Had a similar issue awhile back where after idling I hit the throttle and could not go anywhere, If I feathered it up to full throttle, I could get it going. Once it was going I could run fine until I idled for a bit again. Issue seemed to appear from nowhere. The guys on here suggested adjusting the carb idle screws. They are really sensitive. I set them 1.5 turns from closed and went from there. I would adjust, hit the throttle, feel the response, adjust, hit the throttle, feel the response, repeat... after about 20 times, I finally got it dialed in. (Well, that issue at least)

 

[Chris1956]

OK, I have never heard of a "piston valve". Also, the piston rings are not the issue, I would think. They either seal or not, but do not change their mind.

A bad reed valve ( I think your guy meant to say that) would inhibit good idle. That is not your issue.


It is most likely a buildup of fuel or water in the lower cylinders, is the issue you have. It is a matter of finding out which one and fixing it.