Logo
FULL SITE MENU

1998 90hp Stalling under load

A

aisler

Member
Okay guys, I am at my wits end here. I have a 1998 Force 90hp motor.

Was stalling under load sporadically so I took it in to shop. Mechanic found that water was getting in bottom 2 cylinders and we went through first and replaced all major gaskets, then eventually found a hairline crack in block and replaced power head and rebuilt carbs to ensure warranty. Problem is, that did not fix the stalling under load issue, it actually made it worse.

Was doing it 1-2 time in a day. Now it does it every time I stop and fish a bit. Of course it did not fail when mechanic took it to the lake. Weird thing is i can start it great first thing. run all over and it runs great. I can start and stop no problem, but if I wait 20 minutes or so, then try to go it dies when I give it gas.

Now, if i hit the choke (key) while giving gas, it sputters then goes. If I throw the throttle down hard, sometimes it will go to. If I slowly throttle up it dies. This leads me to believe it is fuel related rather than electrical, but who knows



So to date, the following things have been done by either me or the mechanic (in no particular order).


  1. new powerhead
  2. all new engine gaskets
  3. new fuel pump
  4. full carb rebuild
  5. new primer bulb
  6. new fuel filter
  7. checked vent screen on gas cap
  8. cleaned screen on fuel pick up in tank

Any body have any ideas as I am tired of taking it to the mechanic.
 
Sounds like the float levels need to be checked.What's the idle rpm's(in gear/motor warm)?Should be 750-800.
Replace all the hoses and any inline connectors.
Check the gas for water.
Make sure the gasket behind the pump is there/torn.Check the pump diaphram.
Reset the air screws.Out 1 and 1/16 turn.
Does it help if you pump the ball before you try to start.J
 
Sounds like the float levels need to be checked.What's the idle rpm's(in gear/motor warm)?Should be 750-800. Will have to check actual RPM's but Idele does seem lower than normal when right before it stalls. I can tell if it will stall when I crank the engine. Stronger idle - no stall...
Replace all the hoses and any inline connectors. Have not done this
Check the gas for water. Clean gas.
Make sure the gasket behind the pump is there/torn.Check the pump diaphram. New fuel pump and diaphragms, gasket is there
Reset the air screws.Out 1 and 1/16 turn. Where is this screw?
Does it help if you pump the ball before you try to start. It does not help. It helps if I tap the choke though
 
17.jpgSide of the carb,#14 Air screw. If it helps when you hit the choke.It's possible the choke is defective(sounds funny)There is a diaphram in the choke.
Un hook the choke after you get it running and clog the lines.Go for a ride.
 
Is there any way to test the choke off the water?

Can't get the motor to fail on the muffs, so cant reall do what you are saying unless I am on the lake.
 
Unfortunatly the drive way is where it ALWAYS runs right.
Under a load is where it screws up.
Got any inline spark testers.Install them when you go next time and watch to see if they loose spark.J
 
Okay, maybe you can answer this one as I am not sure it makes a difference. I will explain as best I can

Should the position of the throttle correspond proportionally to the amount that the "butterfly" is open? As an example, if:

Idle = 12:00 and WOT = 3:00

when the Throttle is at at 12:00 the butterfly is closed, at 3:00 it is fully open (horizontal). But what about in between?

At 1:30 should the butterfly be half open? I have been looking at it and it seems that it barely opens until you get throttle handle in the 2:00 position, then it jumps half way and then WOT.

There is a ton of play in the throttle until I hit the ~1:30 position. Also, should there be a gasket between the air cover and the carbs?

Still pretty lost on getting to a resolution, but feel like it will come.
 
Carburetors on outboard motors are not fully open untill the last part of handle travel-------So the answer to the first question is NO
 
I understand that part, but what about at half throttle, should the butterfly be half open?

I am also wondering about the looseness in the first 1/4 of the throttle handle. Does not really seem to move the throttle at all.
 
Ah, that makes sense.

So then that theory is done.


Not really sure where to go from here.

Figured new power head would have fixed the stalling under load, but it must have been a secondary option.


My head keeps wanting to lean toward a fuel/air issue because of the fact that if I hit the choke, it does not bog and die. And if I throw the trhottle down fast and hard, it will not bog.

Honestly I am ready to set the damn thing on fire.

Bought the SELOC book and so far it has not really helped.
 
Factory manual is the way to go. I would pick the clymer over solec but factory over Both of these since they are so vauge and cover like 3,000 diff motors(lol).
 
Try to isolate the choke.The diaphram in the choke could be allowing it to fall on it's face.
On iboats.com The forum section,Find the Force section.the first thread has tip on setting up the linkage.It called a linc and sinc by FrankA That will help with any throttle problems.
 
How do you recommend I isolate the choke?

There are 2 tubes coming off, 1 from carb to choke, the other from choke to motor. Can I hook the one from the carb directly from the motor to isolate it?

I rarely need to use the choke as the engine starts up when cold no problem.

Only time I use it these days is when it starts to bog upon acceleration. If I hit the key, it does not die.
 
TRy anything.
One at a time.Disconect/plug.
If it starts cold with out any help the diaphram might be bad.
Let me ask someone who might remember how to test the primer/choke.
Will get back tomorrow if he answers.J
 
Checking the enricher/choke.
The simplest way is to disconnect the output hose and put it in a jar or something to catch gas. Turn the key on and push in. If it is working fuel will pulse out, not a steady steam.
It should only work when you activate the key/choke.​
 
yes you can blow in the line that comes from the carb bowl, you should not be able to blow through it until you push the button in on the top. you can also put 12 volt to it to make sure the solenoid is working while you are blowing through it.
 
So I assume the reed valves were not changed when the powerhead was replaced, but I will check with the mechanic.

Jerry - I guess I was confused when I kept talking about the choke since it is in fact an enricher. So I am not "choking air" I am actually adding fuel directly to the cylinder when I push the key right?

If so, this would indicate that maybe that top cylinder is not getting an fuel until you hit the key.

It ran great for about 3 hours yesterday and then it started dying under load after that. Could the heat have something to do with it?
 
Running for three hrs.Then dying.I'd look for a restriction someplace in the fuel.
The pick up in the tank/clogged? The tank vent/clogged?
Any old hoses/soft or mushy.The hoses between the carbs??
As far as getting fuel as soon as the motor cranks it starts getting fuel.
The choke shoots fuel direct in the throat.
Old squeezie,water in the fuel?
Any inline connector?They can leak and suck air.
 
Running for three hrs.Then dying.I'd look for a restriction someplace in the fuel.
The pick up in the tank/clogged? The tank vent/clogged? I checked the pick up screen and it did not look clogged. Vent Screen is not clogged, but did not replace the vent hose. Could the gas cap be bad?

Any old hoses/soft or mushy.The hoses between the carbs?? All new. From tank to top carb and all in between.

As far as getting fuel as soon as the motor cranks it starts getting fuel.

The choke shoots fuel direct in the throat.

Old squeezie,water in the fuel? primer bulb you mean? It is new.

Any inline connector?They can leak and suck air. Only in line connectors are the fuel filter, which is new (2nd new one to be sure) and the brass fitting on the transom that connects the main tank hose to the primer bulb hose.


not positive, but it does seem to happen more often with less gas in the tank. also, noticed the connector on the tank itself has some pipe thread tape on it. Does it need that and could that mean there is not a good seal at the tank?

Meeting the mechanic at the lake Wednesday and hopefully it fails with him on it, cause when he took it out, it did not fail.
 
One more question....When you hit the key that engages the enricher, which adds more fuel bypassing the carb right. Does that fuel go into all 3 cylinders or into 1 of the 3?
 
Sounds like the pickup tube in the tank may not extend to the bottom and you start sucking air and loose prime. This is just going off what u said in the prev. reply ( Seems to happen more when tank is empty). Look there and get back with results. As far as those reeds go they may not need to be replaced but would look at them to see if they are in spec. Usually, its just a ajustment. you do have a manual for this engine right? Look at the chapter for them it will tell you all about. I would read this chapter and see if any applies before tearing into them. I only said because its the only part that has not been messed with. Nick
 
I think just the one carb.
Where is the fuel pick up?At the back of the boat? Or the front?
Some tanks have pickup and fill at the front.It means they have to run with more gas in the tank.
Get a couple of 6 gal tanks and bypass your system.
The main tank hose??New ?Old? How's it routed? If it's old and hasn't been changed the Ethanol could have eaten some of the insides.
 
fuel pick up is at the back of the boat at the back of the tank, closest to the motor.

Main tank hose is brand new. Fill hose and vent hose are not.
 
Back
Top