Force 125hp fouling rich?

redfury

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So, I'm reaching out again in search of clues/direction/answers. I've got a 1987 Force 125hp on my 17ft Glastron. The engine sat on my deck on a stand for 3 years before I was able to get it installed on the boat during reconstruction. I put the motor on the boat and it fired up and ran beautifully...better than I had thought actually. So, I brought it to the lake. Within a few outings, at the launch upon the first start up, it backfired like a gunshot had gone off..literally. Scared the crap out of everyone. It blew the small bellow where it expels water out back..split it in half. Couldn't run the engine without the cover off as the exhaust would choke the engine. I ran mostly on my electronics that day. Replaced the bellow and took it out. It ran, but not great.

That's the start of this saga of mine. So, I discovered that the diaphram had ruptured. Figured excess fuel got into #3 and caused the explosion. Replaced it, but was having issues with the motor still. Couldn't figure out why it wouldn't run properly. It would idle, but it would cough and stall after a while of running. I could launch the boat, and take off down the lake and it would start to sputter at the exact same spot every time...regardless of water temperature.

What have I done...I pulled the reed valves and inspected them as well as the engine internals to see if something looked amiss. I took pictures, I cleaned everything up and put new gaskets on and reinstalled. I replaced the head gasket just so I could see the cylinder walls...there's still bottle brush scoring on them. Compression is even across all 4 cylinders. I rebuilt the carbs with new gaskets and cleaned and sprayed them, twice. I added an overheat alarm/light to the dash since I didn't have one. I rebuilt the entire fuel pump this spring and replaced all the check valves because I started to think that there might be a problem with the recirculation system. My first run out, it ran beautifully. I had pulled the flywheel off to check the key and reset the timing on the lake. It ran great. But the 2nd time out after sitting all winter, misfires.

So, I'm back looking at the carbs and the recirculating system. I cut the fuel lines off of the recirculating system and put my vacuum pump on them to see if there was any blockage. Nothing appeared out of order. The bottom most nipple still had the fuel line on it since I couldn't get that off, so I decided to try blowing though it. couldn't, but I could draw a vacuum through it , evidenced by the thin film of 2 stroke fuel in my mouth.

Now, I thought that a bit strange. Pulling the line off of the top 2 cylinders, the lines were fairly clean. The bottom cylinder seems to have an awful lot of excess fuel in it.

The other thing that is bothering me was that trying to adjust the fuel mixture at idle on the lake when it started acting up produced no results. I turned the top carb idle screw all the way in and it kept purring. Neither carb caused the engine to react to input from the idle circuits. Fuel consumption seems higher than it should, but I don't know what I should be expecting from such a large motor anyway.

My set up is an inboard 20 gallon fuel tank up front with a copper fuel line to the back bulkhead with a quick disconnect and a new fuel bulb and a fuel pressure restrictor to avoid overpressuring the fuel pump ....it's really unnecessary, but I have it . Currently I have over a half tank of gas, but I do know that my vent is at least partially clogged again, and I need to clean that out. If that were the problem, I would think that I wouldn't have the rich at idle problem/lack of response to idle circuit adjustment.

I'm trying to not overthink this too much, but it's been frustrating for the last year, and I'd really like to get back to boating without this problem. Mechanically and electrically, the engine is sound, it's the fuel side of it that I'm struggling with. It seems like I'm missing something in my diagnosis.

Last year when it would hit the point of running bad on the lake where it would run great and foul out at the same spot, it would continue to run, but it smoked a lot more than it should, so I'm assuming that I was dealing with a loading up issue, and I had run on both a portable tank ( new ) and the inboard tank with the same results.
 

jerryjerry05

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You said:
The other thing that is bothering me was that trying to adjust the fuel mixture at idle on the lake when it started acting up produced no results. I turned the top carb idle screw all the way in and it kept purring. Neither carb caused the engine to react to input from the idle circuits. Fuel consumption seems higher than it should, but I don't know what I should be expecting from such a large motor anyway.
:
No reaction to the air screws means it's sucking air someplace??
Between the carbs is an equalizer tube, when trying to adjust, pinch off that tube.
That isolates the top 2 cyl. from the bottom 2.
Try to adjust again and see if top or bottom works?

One tiny cough or backfire can blow the port cover gaskets, you have 4 so the chance is real good.
Try the starting fluid test, spray around the intake side and if that makes it cough, stutter, stall?
Then a gaskets gone.??
 

foodfisher

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Excessive Smoking and fuel consumption alert me to the fuel recirculation sysrem. May need a good cleaning.
 

redfury

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If a port gasket was gone, lets say cylinder #3 since it's the fuel pump pulser and also recycles fuel from cyl #4, it could make sense that it is allowing too much fuel to puddle into #4, causing it to act like it is running rich, plus I suppose it's going to make #3 produce less power. It seems like the motor isn't getting up to full RPM with a 17P prop....I'm only seeing about 5000. I currently have the fuel lines off and the coil packs are out of the way. Would there be any benefit to try measuring vacuum at the nipples for the #1 and #3 cylinders to compare against each other for their ability to recirculate fuel properly? I'd almost have to assume that if any of the port gaskets are damaged, it would be #3 since it would have been the over fueled cylinder? Unless it's more likely to be the next cylinder in the firing order to have taken the pressure.

At this point, I'm thinking I might as well just buy and replace the gaskets for all 4 ports and the two for the recirculation plates and be done with it...just service them and see what they look like.
 

redfury

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Something else that comes to mind to me in regards to the recirculation system...I can't blow into the line going out of the plates, but I can pull a vacuum. Looking at the exploded parts diagram, there's a reed that prevents it back flushing and the screen that's no longer available. If I can pull vacuum without registering any vacuum/resistance and can't blow into the plates, I would think it would be plausible to believe that there isn't anything wrong with that part of the system. IF the cover plate was allowing air to enter the cylinder because the backfire caused the gasket to tear/rupture/break and the elbow that connects to the adjoining cylinders plate, it wouldn't allow fuel to be drawn through the reed effectively enough to be drawn to the upper cylinder. Since 1 and 2 were clean, and 3 and 4 had fuel in cylinder 4 as evidenced by the sipl of fuel I got when drawing a vacuum the old fashion way....am I thinking along the right path? So if I put a vacuum gauge on the #1 and #3 cylinder elbow, I should see the same level of vacuum if everything is the same. If the gasket is blown, then I'd have problems creating a vacuum at the elbow....seems like that would be logical.
 

jerryjerry05

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You have T@T? That can make the 500rpm's if the trim's down??
Load? too heavy can hurt too.

Do the starting fluid test if the port cover gaskets are suspect??

The gaskets can be found and when installed, use sillycone and let set overnight.

You said:
I turned the top carb idle screw all the way in and it kept purring.
This shows it's sucking air somewhere.

The screens can be found.
Found 1 on eBay $.99 but over $8 shipping (thief)
I might have a couple? Have to look.
Their free if I have them.
You pay shipping and donate to a local animal shelter and I GIVE them to you :)
 

redfury

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Sure thing Jerry. The gaskets for the recirc plates are cheap, but each port is $12...I bought a vacuum gauge today, I'm going to test my theory on the suction side nipples and checking for cranking vacuum and compare the two, I'll report back when I get that done.

Would it be a safe assumption that if I have a bad port gasket that I could get the occasional sneeze from the motor at idle? I'm feeling that this is the direction I need to head in. If I find one port gasket that's bad, I may just bite the bullet and replace them all, along with the recirc system service.
 

redfury

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I ordered all of the gaskets to do the 4 port plates and the recirc system. I did put the vacuum meter on #1 and #3. I was getting more vacuum from #1, but it wasn't a huge difference. It was there though. If the port cover is leaking some, that could account for the misfire and puddling of fuel on #4 ( assumption based on amount of fuel drawn with vacuum pump.

Thinking about it today, the last time I had it out it had sat for a long time before I had taken it out. It ran great for quite a while, and when we dropped the kids off at the beach, we had troubles with the motor running bad again, so it seems like it's a cumulative use issue. IF, I go through the trouble of servicing the port gaskets, recir system gaskets/screens and I still have a loading issue, where am I looking? I can't imagine the fuel pump over running the float bowls...? As far as the engine at home, running on muffs or a bucket, it'll pop right off with a touch of choke and then fire right off after that without choke or fast idle. I'm not a carb guy, so my understanding is limited to what I've taught myself through video and the clymers manual I have.
 

jerryjerry05

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When your working, change the hoses.
When doing the recirc system, make sure the bottom elbow is clear.
No screens, no problem. Any smoke shops, or hippie stores, head shops in the area?
They sell screens for pipes.
 

redfury

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I'm sure I'll find out, but how delicate are the screens? I'll clean them with brake cleaner if they aren't shot. I drive all over the metro for work, so I can find a shop that would have fine screen material I'm sure. When the gaskets come in, the plan is to remove all of the ports, remove the recirc plates...inspect, clean, replace with new gaskets ( and silicon), let everything sit overnight, reset the carbs to one turn out, check my linkage adjustments and fire it up on muffs. If everything seems well and good, then off to the lake to fine tune the carbs and do an extended running check.

I'm going to check to make sure that both sets of reeds in the recirc plates are working properly. I didn't check the upper one, I'm pretty sure the bottom one was working as I wasn't able to blow through it. I do have replacement hose as I had to cut the original lines to get them off the brass barbs....
 

redfury

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Port covers are off, looks like two of them are carbon fouled in the corner? Anyway, working on removing the old gaskets. New gaskets and sealer in hand.
 

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jerryjerry05

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If using silicone? give it time to cure/dry before you use.
The surfaces must be 100% clean/dry.
 

redfury

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Yeah, I'm still cleaning the gasket material off the engine and recirculation components. Tedious work.
 

redfury

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So I bought two kits thinking that I was getting 4 gaskets, in reality... Two different gaskets. Hmph. I suppose I'm not getting away with using different gaskets, that they need to be the same because of the difference in volume might create its own problems....
 

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redfury

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Is anyone else confused by the document I posted? Mine is an 87 and has smooth surfaces for both the block and the port covers. The gaskets that were on it were the thicker ones that I got in the kit, but it seems like I can use the thinner ones as well....
 

jerryjerry05

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Put enough goop on them and it should be OK!!
Just let it dry before you try to start.
Make sure the tuorqe is set right. 70in.#s
 

redfury

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I was thinking that I'd seal them for sure,but I'd pair them up top and bottom, that way any adjustment can be made via the idle circuit. I'm going to run the thinner ones on top since the thicker ones were originally on it and the lower cylinders seem to be the ones that get wiped out on these vertical engines.
 

redfury

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So, still having trouble with the engine. Got all the gaskets redone, sat overnight. Upper carb won't respond to the adjustments.. Run it all the way down and there's no response. So I decided to pull the upper carb. It's clean, the float is blocking me from being able to blow air through it while I am holding it upside down. So, off to the manual and I notice this little gem. Says the tube must contact the main nozzle. I'll pull the other carb to see if it is or not.. That one was reacting to me adjusting the idle circuit. I know that have spark on all 4 cylinders, the spark plugs all look the same, they were all brand new on my last outing. I'm not a carb guy, so I'll take any advice you guys have.
 

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