Force 50hp 1 carb approx 1992 - won't idle

Tuni

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My Force 50hp 1 carb fires up with the choke handle up, revs high, and can run all day. I can't lower the choke handle to engage the throttle...it dies. I cleaned carb twice with carb cleaner and adjusted carb float (horz with carb body), I also replaced needle valve. The primer valve doesn't 'click' when ignition key is pushed in, but motor still starts right up with choke handle up and throttle in neutral. Both cylinders are at 125psi. Mixture screw is at 1-1/4. What can I try next to get this thing to idle without taking it to a shop? I'm not a mechanic and enjoy working on puzzles....I think I'm missing something on this one. Thanks.
 

jerryjerry05

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If at all possible, try to include serial #s or model #s.
​They made 14 different models and a lot of changes.

Your primer.
​It has a rubber diaphragm like your fuel pump and it can go bad.
After it starts, pinch off the lead from the primer to the carb.

The primer no click, get a test light.
Turn the key on, hold test light at green lead and hit the key for primer.

The air screw might need to be out farther??
​They suggest 1 1/4 to start, but some need to be out more.
​One customer his 86/85 needs to be out 3 turns to even think about idling??.

Choke handle???
Pics?

Your carb have a white plastic plug on the top?
Under the plug is the mid range jet.
Make sure it's clear.
 

Tuni

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Jerry,
​My ser# is OE 011553. Even though the cowl says Force on it, the serial number on the boat is a Mercury label.

​I'm assuming you mean to pinch off the lead to the carb bowl (which is the bottom tube). What will that tell me? Would this effect carb idle if it doesn't work? I'd like to get this thing running first, then fix the stuff broken.

​Maybe wrong verbage on choke handle. My remote has two handles: so may its the throttle handle I'm referring to that needs return to stop before I can put the other handle in gear. Sorry about that.

​Yes my carb has the white plug. I took it off on one of my carb cleanings and tried to get the nut out. Is there a trick like oiling? Screw driver fit the slot but it was very hard to turn. I didn't want to screw things up so I didn't do anything. The same with the nozzle jet. I heard you don't want to mess with the 'straw tube' in the middle so I left that one alone too.

​I'll start with the air screw (easiest). Then remove carb and try to get the needle out and clean.
​Let me get to work on your recommendations and I will update you with my findings.
Thanks for your help Jerry.

 

Tuni

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So far this is what has happened: I started up the motor and turned out the air screw at least 3, then 4 turns, then lowered the throttle down and it still shut down. So I turned screw back to 1-1/4, started up and pinched off tube to fuel bowl and nothing happened. While motor still running I pushed key in and motor stopped.
​I now have the carb on the workbench to try and get the nut off so I can clean jet etc.
 

Jiggz

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Have you checked for sure if both cylinders are firing by doing the cylinder drop test (pulling plug cable one at a time and listening for change in engine rpm)?
 

Tuni

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Kinda good news. I put the carb back on and adjusted to 1-1/4 (air). Started right up, but shuts down when going to idle. I took 1 plug off and it started right up and no apparent difference to sound. Connected it back up and pulled the other cylinder....it didn't start right up. After trying a few times it started but very rough sounded. Did this twice to make sure I knew which 'pack' needs attention! If this isn't the problem it's sure going to be an issue down the road. Is there a instrument test to check the packs out? Thanks Jiggz
 

Jiggz

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The next step is to do the process of elimination by switching known working parts with suspected broken parts. In your case, you can start by switching the coils. Just make sure you switch all associated wiring for each coil and not just the wire that goes to the plugs.

If the problem follows, i.e. if from top cylinder the misfiring goes to bottom cylinder after switching then the coil is bad. If the problem did not follow, i.e. it stayed at the top cylinder then both coils are good.

I am presuming you have the Prestolite Ignition system. Hence, there is only on CD pack feeding both coils and spark plugs or cylinders. Still, you should still be able to switch the circuit feeding the top to the bottom cylinder. This action involves more wires (trigger wires and coil wires) so I suggest you make a drawing of the wiring or take pics as you remove them.

Again, make sure all wires are switched and then see if the problem follows.

As for instrument to check CD modules or packs, it's called a DVA which measures the voltage output of the module and can even be used on coils, stators and triggers.
 

Tuni

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I can do the swap, but not for a few days. I will update probably early next week. Thanks for the info.
 

jerryjerry05

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Pinching off the lead to the bowl.
​That stops excess fuel from getting to the bowl and flooding the carb.
If the diaphragm in the primer was bad it could push extra fuel into the carb.
 

Tuni

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Well it's been way too hot to work on the until now, but I did some thinking and hope it makes sense. I wanted to be sure I checked the spark correctly before swamping the wires and coils around, so I hooked a plug tester to each plug and started the motor. Each tester was lighting up smoothly, therefore I'm hoping this means my coils are both ok. I'm lost for next step. I'm guessing it's back to the carb. Can I override the kill switch to make sure that it's not involved with carb idling?
 

jerryjerry05

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If both plugs are firing? the coils are probably good.
You have a tach?
The dying at idle: could be the idle is too low.
​Needs to be 800 in gear 1100=/- on the hose or at idle.

​Any fuel coming back out the front of the carb?
 

Jiggz

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Try raising idle speed first and see if that'll solve you problem. If not do the following:

If both spark plugs are firing the next step is to verify fuel/air mixture is getting into the cylinder. Or that no water is getting into the top cylinder. Based from your drop cylinder test, #1 (top) cylinder is the suspected not constantly firing cylinder.

Do a quick test run of the motor for about 30 seconds. Make sure cooling water is connected. Stop the motor and quickly pull top spark plug and inspect for water or condensation. Better, yet take a pic and post it. If good amount of water is getting into the cylinder there will be water or droplets on the face of the plug. If there is only a small amount of water, then there will be steam cleaning indicated by a shinny clean dry spark plug.

If there's no indication of water intrusion then the next step is the paper wet test. Remove #1 plug, activate the kill switch so motor will not start. Have a second person do the starting while holding a clean dry piece of paper in front of #1 hole about 4~6 inches away. Crank the motor for about 3 revs. If fuel is getting into cylinder you will have a good size pattern of fuel wetting. For comparison do the same with #2 cylinder.

If there's not enough fuel getting into top cylinder, that is an indication you might have damaged reeds. Next step is dismount the carb and intake adapter and inspect the reed's V block .
 

Tuni

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Jerry, Yes I have a tach and will check the rpm's. No fuel is coming out of the front. Will advise results.
 

Tuni

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I need to eat crow (a little) 'cause I have a auto tach, and my boat tach on the dash isn't working. I turned the idle screw inward to full turns but it didn't help. I then did the water test on cylinder #1. Ran the motor, shut off and took the plug out. There was no steam coming from the hole. Attached are pictures of the result. Looks good to me. I will now move to the paper test. I do not know where the kill switch is on my Force 50hp, it's around a 1995 (Merc ser # OE011553). I figure it won't idle so why bypass the switch?
 

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Jiggz

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The plugs seems to indicate fuel wetting which should be OK as long as it is not too much. #1 plugs seems to be getting fuel and maybe running rich or misfiring or not firing at all. Try switching the plugs and see if the problem follows. Or you if you have extra new plugs try it on #1 first and see if that will resolve your issues.

If you decide to dismount the carb again, go a step further and dismount the intake adapter and the reed V block and do an inspection. Post pic if you can.
 

Tuni

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I found the kill switch on the remote throttle. It was underneath a plastic cover - basic toggle switch! I am half way through the paper test and the battery is now needing a recharge. But for cylinder number 1 the paper didn't come out wet at all. Looks like it pushed dirty air onto paper. I was only about 2" from hole because I want to be the same distance when I test cylinder 2 (it's in the body and I can't go back more than about 2").
 

Jiggz

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If such is the case, then dismount the carb and check the reed block for broken reeds or unseated reeds.
 

Tuni

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dismantled the reeds and attached pictures. Both appear to be ok (yea I'm a mechanic....right) to me. I couldn't find any separation where 'light' penetrates. I mentioned way back I enjoy puzzles but this is starting to get me down. Should I start all over and double verify or do something else?
 

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Jiggz

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Those reeds look perfect. Can you post a pic of the wet paper test on both cylinders? And try switching the plugs or use a new plug and do the drop cylinder test again to see if the plugs could be causing your issues. Obviously, you need three things to get combustion in each cylinder, i.e. compression which you have, spark which you tested you said you have and then fuel-oil and air mixture. With these three being present you should have combustion in each cylinder.

Now if you have compression and spark and the reeds are in perfect condition, then the only reason you cannot get fuel oil air mixture in a cylinder is if you have leaks in the crankshaft seals or if the affected cylinder is the same cylinder the fuel pump is and has a torn diaphragm or leaking.
 
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