1988 Force 85 hp boggs @ WOT, #1 Cylinder Fouling

[dngbt5]

What I have:

1988 Force 85 hp On a Bayliner Capri 1700 (856X8A)

What I have done:

-Replaced impeller (moves water great)
-Checked compression 125 on all cylinders when cold
-checked all ground and ignition wires for solid connections
-replaced Trigger
-replaced all fuel lines and bulb (bulb holds pressure when running)
-Checked that fuel tank vent is clear
-Cleaned fuel filter(almost every time I go out)
-checked for spark - have good spark on all cylinders
-replaced fuel pump diaphram
-removed and cleaned all carbs
-set external jets to 1 1/4 turns out
-run sea foam in gas
-run exactly 50:1 mid grade or premium (whatever doesn't have ethanol) fuel mixture

My problem:

-Motor will take off great at WOT and planes out, but then boggs down after 20 - 40 seconds or so. I can then return to 3/4 throttle and it runs fine as long as I do not increase the throttle past 3/4 throttle. If I increase the throttle the motor then boggs again. If I leave the throttle at WOT too long it completely fouls the Top #1 cylinder and can no longer even run at 3/4 throttle. After checking all three plugs it is only the #1 Plug that is very dark, dirty, and sticky.

-My motor starts every time and idles perfectly. I have not checked timing with a gun since replacing trigger, but i dont think it would cause only one cylinder/plug to foul.

-Additionally I have not noticed any fuel coming out of the overflow on any of the carbs

- I have noticed a small amount of exhaust leaking in the lower unit recently also. Not sure if that would cause one cylinder to run dirty?

- I was thinking my coil could be heating up and failing but I can run at 3/4 throttle all day so I am doubting that possibility.
-Could I have a float sticking?
-Needle not seating fully and allowing too much fuel to flow? Or is it running out of fuel?
-Exhaust valve/gasket issue?
-Cracked/Broken Reed ( I inspected them when I removed the carbs but forgot to look underneath with a mirror and light)
-Am I not getting enough air to that cylinder?

 

[bentle]

Re: 1988 Force 85 hp boggs @ WOT, #1 Cylinder Fouling

You need to warm up the engine first 10-15 minutes. Then pull plug install compression tester and see what you get. Cold metal shrinks warm or hot expands and when we run our motors they get warm so you want good compression while the motor is warm. You may be loosing compression on that cylinder when the motor is warmed up. If a reed was broken or even badly bent they you would notice some spitting back out of the fueltiny intake of your top carb and a slight popping. Make sure your battery is well charged and ground thought spark plug wires to the engine block.

 

[mikes 86]

Re: 1988 Force 85 hp boggs @ WOT, #1 Cylinder Fouling

mine does exactley same thing, this didnot start until after i rebuilt carbs so i dug little deeper and found needle on top carb sticking have not got a chance to go to lake yet going to check on thurs. will let you know what i find if it is not it i do not no what to look for next, hard to figure out !!!!

 

[bentle]

Re: 1988 Force 85 hp boggs @ WOT, #1 Cylinder Fouling

Timming is very important on any motor at idle as well as wot. I wouldn't run her any more
at wot until you can get her timed right. Static time is 28 btdc wot. 30 btdc running in or on the water wot.

 

[jerryjerry05]

Re: 1988 Force 85 hp boggs @ WOT, #1 Cylinder Fouling

Any inline connectors in the fuel system?They can suck air.
I had to clean a carb 3 times before it worked.
A cold motor will give the same comp#s as a warm engine.Reeds will not nake a difference in comp readings.Pull the carbs and check the reeds.
The top carb check the seat for the needle.Sometimes the rubber will swell and partially block it.
Fouling out? What's the needle look like? Any cuts or grooves in the needle?
You rebuild and change the welch plugs??Or just clean it?

 

[dngbt5]

Re: 1988 Force 85 hp boggs @ WOT, #1 Cylinder Fouling

Thank all of you for your quick responses and advice. I am in Kansas City, MO for work till Thur. but I Definitely pull the carbs and check the needle
and the reeds when I get back. I ordered a new needle already, I am hoping it is in by Fri. I just lined up a timing gun also. I will let ya know what
happens.

 

[stubtail]

Re: 1988 Force 85 hp boggs @ WOT, #1 Cylinder Fouling

I have experienced a similar bog-down @ WOT, and have noticed excseesive play between the threads of the timing adjustment rod and the nylon connecter off the towershaft up to 1/8" (the end without the locknut). It may be possible for the timing to drift during operation sufficiently to cause a power loss.
Just a thought.