1986 115 merc I6 bogs under full throttle load.

[Shwinkyyy]

So I took all the carburetors apart, and i gave everything a good cleaning, put in new spark plugs, and threw some seafoam in with a tank of fresh fuel. Engine idles great, and i can open her up good on the muffs. As soon as I put her in the water she will bog down and stall when I go full throttle. This was all tested tied up so I didn't really have a chance to run her down the water. Shop is tied up for 2 weeks, so in the meantime I'm seeing what I can do on my own.

 

[Texasmark]

Service manual on my current engines, not the I6 but being carbureted, the same thing applies (surely), state that the final low speed needle adjustment is on the water doing the Hole Shot. If you bog in the shot, open the needles a little bit at a time until it takes throttle. You may be running too lean and not enough fuel is available from the idle jets (before the main jet has time to take over) arn't supplying adequate fuel.

 

[Shwinkyyy]

Ok thats probably where I am messing up then went out 1 1/4 like I was supposed to but haven't done the final adjustment. Is rough idling normal when your doing such adjustments?

 

[Brosef]

I had similar issue turned out to be the primer bulb

 

[Texasmark]

I had similar issue turned out to be the primer bulb

Primer bulb on no hole shot? Was it clogged with little tan chips of crud, blocking fuel flow? I had that happen on a 10 year old OEM fuel line/bulb running E10. Whether it was the fuel or the line I don't know. The larger pieces did have curvature so I assumed it was fuel crud. Once you popped the coating off the inside of the line it seemed to be (grey) silicon and intact.

 

[Texasmark]

Ok thats probably where I am messing up then went out 1 1/4 like I was supposed to but haven't done the final adjustment. Is rough idling normal when your doing such adjustments?

My manual on the later 3 and 4 cylinder 90 and 115 shows 1 ½ turns from 2 fingers tight for starters.

 

[Chris1956]

Those IL6s and other inline motors from the 70s and 80s need to have the idle mixture set richer that expected, or they bog upon acceleration. Generally the 1-1/2 turns open is too lean for smooth acceleration.

You will need to adjust them in the water under load. Likely the top carb idle mixture will need to be open more then the mid carb, and the bottom carb will be the leanest. Adjust in 1/8 turn increments, testing acceleration after each adjustment and start with the top carb.

just try to have a acceptable idle, as that is likely the best you can do. Take your time. A buddy to drive the boat is a nice to have..

 

[Shwinkyyy]

So i hope I'm not breaking any rules here, but we can WOT, but now it won't plane off at WOT. It will make a little "pop pop pop" and want to pick up a little bit but so far can't get it to go faster than 8mph

 

[Shwinkyyy]

I'm not sure if that counts as a separate issue but I didn't want to flood the board with multiple posts, were on the water now tinkering at the dock so if a quick reply is possible it would be much appreciated

 

[Texasmark]

Chris is your man on your vintage engine.

 

[Shwinkyyy]

So an update, turns out it was a spark issue. Cylinders 1,3, and 5 are dead. We are running a multimeter to test to see if its the cdi box, or if its the coil packs. Definitely explains a lot ofnl the issues

 

[Shwinkyyy]

Yep... its a cdi box. Goodnight everyone time to order a part.

 

[Shwinkyyy]

So we now have yet ANOTHER update.. put the cdi box in got spark back to 1,3 and 5 take the boat out for test. Still won't go passed 8 mph. Pulled it back out again ran over all of the wires and connections. We find a weak spark on the cylinders now. Went through wiring diagram and fixed previous guys mistake. Finally drew the conclusion that the motor needs a new stator put in. Anything I should know about installing a new stator?