1990 Force 90 Won't Idle/Rough Idle in Neutral

[Derrick Fronckowiak]

I bought a 1990 Bayliner Capri (with a Force 90 engine) in April 2014, It ran all summer long (I fished and crabbed in Puget Sound up in Washington) and a little bit in the beginning of summer of this year and that's when the problems started. I was having real problems getting it to idle. It almost seemed like it was getting starved of fuel. I checked fuel lines (replaced some if they looked brittle or questionable), fuel quality (made sure I had good fuel with no water) and even used a portable tank straight connection to the engine just to eliminate any plumbing, fuel venting or other fuel delivery issues as possibilities. I started to think about the carbs being gunked up so I got kits and rebuilt all three carbs. Tried adjusting idle mixture and idle speed. I can keep it idling if I maintain a much higher than normal idle speed (1100+ RPM), but the book calls for 700 to 800 RPM Idle speed. One time I thought I had it purring pretty good, but when I put the boat in the water it was hard to start and would not idle well enough to take the shifter out of the start position (pulled out of detent and all the way forward) and into neutral without the motor sputtering and quitting (so going from neutral and into gear is pretty much out of the question). That's pretty much how it is now whether it's in or out of the water.

I like to believe I have eliminated all the possibilities for fuel delivery or metering as a possibility and think I should check connections and scrutinize electrical/ignition. But where to start? What is typically the most likely culprit. Those SELOC manuals are OK, but very general in nature and cover a wide variety of type/model/series engines. Oh by the way I've also done primary and secondary compression tests on this motor. Primary tests look good as there are no observable case leaks, secondary compression tests reveal slight split, but within limits (#1 Cyl 121 PSI, #2 Cyl 130 PSI, #3 Cyl 129 PSI)-so a little low on #1, but still with limits.

Please impart your vast warehouse of knowledge upon me (I can and have torn down and rebuilt four-stroke automotive, and aircraft engines, rebuilt fuel metering systems, and rewired engines, but this two-stroke stuff,,,whoa! I'm dumbfounded).

 

[Frank Acampora]

Fishing and crabbing uses a lot of slow speed time. These engines do not like to run slowly. The plugs tend to foul rather quickly. First clean or replace the spark plugs. Fouled plugs will cause poor idle, hard starting, stalling, or all three. I always carry an extra set of plugs. If I see someone with a Force having trouble the first thing I do is trade plugs. (Spark plugs will last almost forever and cleaning them is almost always adequate.)

Then set the idle to 700-750 IN the water IN forward gear. (since different props load the engine differently, idle speed in neutral is not a good indicator however it will usually be around 1000 RPM)

 

[Derrick Fronckowiak]

[FONT=&quot]Frank, thanks for your guidance and advice. I went and got new plugs, but no improvements and couldn't get her started (need to make sure my battery is good though). I heard that the RPM needs to be up over about 1800 before it is strictly relying on the mags for ignition. In other words, a low battery charge (even though there may be cranking amperage there) can cause starting and idling problems. Is that true or a myth? I totally get what you are saying about adjusting idle in forward, just a bit shocked that the SELOC manual doesn't say that. There I was trying to achieve 750 to 800 RPM in neutral. Once I get her idling stabilized I'll get her in the water and adjust the idle in gear.

As far as cleaning plugs goes, what do you recommend? These are those NGK plugs that have the center electrode that doesn't protrude past the end of the plug, so there is no plug gap to be set and the insulator appears to be right there against the plug wall. The old plugs do appear to have a lot of carbon build up on the insulator.

Any other guidance or suggestions?[/FONT]

 

[jerryjerry05]

Make sure the linkage opens all 3 carbs at the same time.
The air screw is set at 1 and 1/8th out for initial setting.
The plugs, just use a wire brush or wipe on the pants leg.
They hardly ever go bad. I used a set for about 10years.
Idle 1100=1200 in N.750-800 warm and in gear.

Once your motor starts it should keep running on it's own.
You shouldn't need a "hot" battery to keep it running.
If you do then the stator / regulator might be bad??

The trigger leads, under the shrink wrap the wire can break.
I change the connectors on all the leads, stator too.

 

[Derrick Fronckowiak]

Jerry, Thanks for the advice. I'll check all those things.