redfury
Commander
- Joined
- Jul 16, 2006
- Messages
- 2,655
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.
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.
