I have WOT, idle, and nothing in between..

[erikpn]

What could be causing this? It'll run fine at WOT, it'll run fine at idle, but anywhere in the middle, I get lots of misfiring and surging and the outboard won't hold a steady speed? '87 force 35 has given me so many headaches..

 

[john from md]

Re: I have WOT, idle, and nothing in between..

First thing to check is your fuel diaphram as it may have a tear in it. Second is to remove the carb mounting plate and check the reeds.

If it is running bad at midrange and smoking alot, chances are one of those two is the problem.

John

 

[erikpn]

Re: I have WOT, idle, and nothing in between..

First thing to check is your fuel diaphram as it may have a tear in it. Second is to remove the carb mounting plate and check the reeds.

If it is running bad at midrange and smoking alot, chances are one of those two is the problem.

John

fuel diaphram is fine, I replaced the fuel pump last week. Reeds are something to look into. It does smoke a lot too.

 

[Camo Joe]

Re: I have WOT, idle, and nothing in between..

Something in the carb jets.............pull it and clean clean clean............all circuits.............

 

[john from md]

Re: I have WOT, idle, and nothing in between..

The force has an idle circuit and a main metering circuit. The only jet that is replaceable is the main metering jet. Mid range is a mix of idle circuit and main metering circuit depending on the trottle plate position. If the idle circuit is blocked, the engine doesn't start and idle. If the main metering jet is clogged, you won't get any speed. There are no mid range jets in this engine.

Additionally, if your engine is running poorly and backfires, it can tear the fuel diaphram in short order. Just because you replaced it recently doesn't mean that it hasn't gotten torn when the engine backfired.

John

 

[Camo Joe]

Re: I have WOT, idle, and nothing in between..

Crap in pilot jet..................Clean all jets ..............

Its prob backfiring and spitting back through the carbs on acceleration.........also look for vacuum leaks.......gaskets , hoses, etc.

 

[Frank Acampora]

Re: I have WOT, idle, and nothing in between..

Got to agree with Camo---There are several metered holes at the top of the carb both in front and behind the butterfly plate when it is closed. This is the idle and low speed circuit. They increase fuel delivery as you open the butterfly when the engine is running slowly enough that the venturi will not atomize gasoline due to low air flow. These function up till around 2000 RPM If one or more are clogged, the engine will run like crap, go lean, and die, until you get the rpm high enough for the venturi to function. Clean the carb! Before you do other steps.

 

[erikpn]

Re: I have WOT, idle, and nothing in between..

The force has an idle circuit and a main metering circuit. The only jet that is replaceable is the main metering jet. Mid range is a mix of idle circuit and main metering circuit depending on the trottle plate position. If the idle circuit is blocked, the engine doesn't start and idle. If the main metering jet is clogged, you won't get any speed. There are no mid range jets in this engine.

Additionally, if your engine is running poorly and backfires, it can tear the fuel diaphram in short order. Just because you replaced it recently doesn't mean that it hasn't gotten torn when the engine backfired.

John

I replaced it 3 days ago. It was running poorly before then and the old diaphragm wasn't torn either.

Am in the process of cleaning the carb right now. Will take a look at the reeds since they are right behind the carb.

 

[Camo Joe]

Re: I have WOT, idle, and nothing in between..

I replaced it 3 days ago. It was running poorly before then and the old diaphragm wasn't torn either.

Am in the process of cleaning the carb right now. Will take a look at the reeds since they are right behind the carb.

Yep..........make sure it doesn't have a varmint in there............

 

[erikpn]

Re: I have WOT, idle, and nothing in between..

I appear to have destroyed my carburetor. The needle of the needle valve seems to close a orifice surrounded by a tiny rubber bushing. The carb cleaner has swollen it closed. There was no instruction in the service manual to remove this, no part number and I was not even sure it was rubber, and if there was a way to remove it then it would require special tools.. so it does not look like it may even be a replaceable part. Do I need to buy a new carburetor now?

 

[compute42]

Re: I have WOT, idle, and nothing in between..

crap.. this may have happened to me... lots of carb cleaner and now runs aweful at higher throttle settings.... HMMM....??

 

[Camo Joe]

Re: I have WOT, idle, and nothing in between..

Is this your carb? Do you see that part here?

 

[Camo Joe]

Re: I have WOT, idle, and nothing in between..

If not try here and click on your ser. #......................

http://www.boats.net/parts/search/Merc2/Force/35 H.P. (1987)/parts.html.

 

[erikpn]

Re: I have WOT, idle, and nothing in between..

That's my carb, and its the part right above the inlet needle #31. The tiny rubber thing. It does not come out as part of the needle though, and a small metal ring is holding it in place. I have temporarily pushed a wire through it, which seems to have opened it up. The needle can still close it when the carb is turned upside down. Hope it works.. didnt have time for a test tonight.

 

[byacey]

Re: I have WOT, idle, and nothing in between..

That isn't the idle needle, that's the fuel inlet needle and seat controlled by the float. The idle needle is part #27. Check this, and the bore it threads into and all the air passages for dirt and crud.

Some of the fuel inlet needles have a viton neoprene tip on them which may have deteriorated. If so, this must be replaced.

 

[Camo Joe]

Re: I have WOT, idle, and nothing in between..

That's my carb, and its the part right above the inlet needle #31. The tiny rubber thing. It does not come out as part of the needle though, and a small metal ring is holding it in place. I have temporarily pushed a wire through it, which seems to have opened it up. The needle can still close it when the carb is turned upside down. Hope it works.. didnt have time for a test tonight.

Yes ....it comes out..........If the needle tip or seat is damaged in any way replace them (even if the needle end is indented any).....with a
KIT, VALVE SET REPAIR

Go here click on your model # ......they have the kit.........The carb being clean and in good working order is a must if you want the engine to run right...........Working on carbs usually seperates the men from the boys....remember clean means clean.
http://www.boats.net/parts/search/Merc/Force/1987/parts.html

 

[erikpn]

Re: I have WOT, idle, and nothing in between..

Well, the midrange misfire/rough running has died down considerably in neutral. And the issue with fuel spitback seems to be resolved. I still have surging/rough running at midrange on the water though. What else could it be? Lots of smoke now.

I just noticed the fuel lines running from the tank are 3/8" and the fuel lines on the engine side are 1/4". Is that normal? Could that be causing the issue?

Also, I have no thermostat. Engine running cooler than it should for a long time, could that be responsible?