Issue when throttling (stalling/nothing) 90HP Force Outboard (Probably early 90s)

[zaufe]

I bought a used boat, 1992 Maxum 1800XR with a HP Force 90HP outboard. I cannot determine 100% the outboard info (plate is missing) other than I assume its original with the boat and matches a lot of descriptions for the 89-92ish model.

I'm new to boating, but not afraid to get into this and learn the mechanics of the engine..

Having issues when the boat is nice and warmed up, when putting in gear and applying throttle, it will sort of "stall" out. It doesn't completely stall though, but engine just cuts out (sort of like just turning off the key) - doesn't sputter or anything. If I go fast between neutral and forward throttle it will "catch" or something and will go without an issue... Once I get it "in gear" as long as I don't go too low on throttle its fine. It does the same thing with reverse.

RPMs run around 800 during the neutral, very low throttle period. Occasionally it will just stop until I put it back in neutral (if in gear) or restart it (if in neutral).

I plan on getting a compression test and checking over spark plugs/etc... but looking for other advice before I take it into a mechanic and spend more on it if its something really simple.

Otherwise boat seems to run well - I had it going mid-30's and stayed under 5k RPM's (from what I can tell that's the max for this make/model on full throttle).

As you can imagine, this makes loading the boat on the trailer quite the challenge

 

[pnwboat]

There is a topic at the top of the Forum labeled "Carb and timing tutorial" with a link to a You Tube video. You might want to take a look at it to make sure the carburetors and ignition timing are set correctly.

 

[zaufe]

Yeah, was wondering if there might be something to try there.. Once I get the compression checked and all that, I might work on that. I also have the Clymer shop book on it, which migh have some, but a youtube would be great

 

[zaufe]

I had the carbs redone, this seemed to take care of the issue. One of the floats were bad.

 

[Jiggz]

It's either that or the mechanic just adjusted the idle setting (or the idle air fuel mixture screw). To start with, 800 RPM in neutral is too low. The correct settings should be at least 1000-1200 RPM's in neutral which almost always translates to 750 RPM in gear idle in the water (all depends on the size of the prop). I'm saying this because if the motor runs fine as soon as you get it in gear and reaches 30+ MPH, then it tells me the carb's floats are set correctly to start with.

 

[zaufe]

Hmm.. the idle speed is still the same, but I do see a drop when I go into forward gear (pretty sure this was true before this last fix) - was looking at the Clymer manual, and it shows 700-800 rpm in idle speed in forward gear. I might make this adjustment myself then... I did have one time it stalled out after the fix, but it stalled out at idle in forward gear.. before it would just shut off (no stalling, more like I just turned the key off). So that makes sense.

Does this adjustment have to be done in the water, or will muffs suffice?

 

[Jiggz]

You can do the adjustment while on muffs for a start. And then just fine tune it when you get into the water. Personally, I set it around 1100~1200 RPM on muffs idling. So when you get into the water, at least it should not stall on you when you get it in idle in gear. If the idle is too high you can always come down during your fine tuning. Make sure the idle air fuel mixture is set accordingly. Usually this is 1~1 1/4 turn out from lightly seated. Again, you can start with higher opening 1 1/4 just to make sure it doesn't stall on you.

Each motor has a differently settings, just make sure the idle air fuel mixture screw doesn't get set below I turn out from lightly seated. Having high idle rpm in neutral is also detrimental to the engine's clutch dogs which can prematurely wear it out. Remember, when shifting in gear always be snappy. Do not slowly slide it in causing metal grinding on the clutch dogs.