1994 Merc Force 90HP Stalling when throttling up (most of the Time)

Tcapper

Cadet
Joined
Nov 1, 2023
Messages
17
Hi all, kind of a long explanation. Had an issue with this motor a while back, wouldn't idle or throttle up. New fuel (premium) and finally took it out this weekend. Fired right up and idled perfectly, let it warm up, put in reverse and it stalled. Restarted and worked as is should. Put full power across the lake, slight bog but picked up and went. Next morning, fired up and worked as it should, until trying to move to another spot after about an hour. Started up, let it run for a short bit, put it in gear and throttled up and it stalled. Tried several times, and finally picked up and went.The same issue throughout the day and also today. I have to restart several times and put the hammer down until it finally moves. When it goes, it runs perfectly at high and low speeds. I'm leaning to dirty intermediate (low speed jets) or possibly a failing fuel pump. Looking for anybody that has had the same issue or a little more insight. I'm gonna be pulling the carbs and running them through my ultrasonic cleaner. Prefer not to pull everything apart if I don't have to. Thanks in advance.
 

Tcapper

Cadet
Joined
Nov 1, 2023
Messages
17
Hey thanks, wish I would of thought of adjustments while it was at my cabin. Frustration makes the thought process unreliable. LOL. Gonna run some Seafoam through it as well hopefully gonna put it back in the water next weekend. If adjustments don't do it, I guess they're gonna come off and cleaned.
 

Jiggz

Captain
Joined
Oct 23, 2009
Messages
3,909
Can you report on the idle speed on the following situation:
- RPM at idle neutral on muffs on the driveway
- RPM at idle neutral in the water
- RPM at idle in gear in the water

Typical RPM for a fully functioning motor is, respectively as above:
- 1000~1200 RPM
- 800 ~ 1000 RPM ( a little loss of rpm due to back pressure from the depth of the water, meaning a little exhaust is not being pushed out)
- 700~750 RPM (a little loss of rpm due to prop load)

After adjusting the fuel/air mixture screw your rpm should be close to the above. If less, then adjust idle screw setting. If too high, this is not good for the clutch dogs which can get worn out or even break due to high impact upon engaging at high rpm.
 

Tcapper

Cadet
Joined
Nov 1, 2023
Messages
17
No tach. I don't think my old school timing gun does 3 cylinder, but I'll try to check.
 
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