So, here goes. Surprise! An old Merc that won't idle! Serial 6559729.
Backstory, I bought the boat about 2 years ago as "a good runner". Well, long story short, it's not a good runner. Backstory on me, I consider myself reasonably handy, know my way around a garage a bit, but by no means consider myself a pro. I don't have a ton of experience on outboards.
On to the boat:
Last year I was able to get it idle reasonably well, it would idle fairly well, but it was super rough and would occasionally stall. First couple trips this year it was about the same, but now last weekend it just wouldn't idle to save its life. I fiddled with the low-speed jets to no avail.
So last year this is what I did:
New plugs (the ones in the attachments have about a full Minnesota season on them, probably less than 20 hrs.)
New stator and pickup. (Replaced more because the insulation was falling off them)
Replaced any other questionable wiring.
New rectifier. (Wasn't getting a tach signal)
Rebuilt carbs, good cleaning, new needle/seat/gaskets.
Checked timing, this SEEMED ok, but I was struggling to get a consistent reading.
New fuel line, tank to motor, new bulb.
At the end of the season I winterized with sea-foam, the run for a half-hour with a heavy sea-foam mix, then spray sea-foam in the carbs until it dies trick. Bit of sta-bil in 5 gallons of fresh gas.
Prior to the new season, the only thing I did was add a new fuel tank, went from portable to permanent (not sure if that's relevant.)
Beginning of the season, started right up on the muffs. Idled reasonably well, same as last season, rough and would occasionally stall. Topped off the 14 gal tank, and off to the lake. No change in idle quality, but it still ran strong once underway. Then this last weekend, I couldn't get it to idle to save my life.
Cold start seems OK. Set the throttle open a smidge, choke it, starts right up. Let it run around 1500 RPM for a couple minutes. When I pull it back to idle it drops to around 900 RPM, chugs for a bit, then it sputters and dies. Once it's hot, it'll fire right back up, idle for a beat or two, then chugga chugga chugga, dead.
Getting into gear is a fun exercise! But once underway it'll putter around at 1100-1500 RPM just fine, and at wide open it'll get to just over 5000 RPM and push the boat around at 35 MPH on the GPS.
After it started acting up this year I dug into it again:
Compression checked: 130,130,130,120
Checked the bleed hose/check valve (I disconnected the hose at the top, I was able to suck but not blow)
Verified float height was 11/16" (I wasn't able to get a real good measurement, no ruler thin enough, so I'd call it 11/16 +/- 1/16)
Re-set low speed jets, with no success.
Attached are what the spark plugs look like after about probably 20-30 hours.
In a prior thread it was mentioned that the bleed inserts tend to fall out, and that can cause bad idle. I pulled the bypass covers off, see attached pic. I don't know what these are supposed to look like, but to my untrained eye I don't see any sort of nylon/plastic insert in any of the three holes. Prior wisdom suggested an 8/32 set-screw with an .040 hole in it. These holes look to be about the size that you'd shove an 8/32 screw into...
Also in a prior thread, thank you racerone, it was mentioned to "Look at reed valves , labyrinth seal grooves in the reed blocks, bottom crankshaft seals, piston and ring wear, bleed inserts..." From what I understand with this motor, the reed blocks are hidden underneath the bottom of the crank shaft? And others have suggested that the reeds in this particular unit are fairly resilient. Those last suggestions (other than the bleed inserts) would require some serious tear-down that I'm hoping to avoid. Are there any checks I can do to test these that don't involve removing the powerhead? From what I've read about compression testing, the numbers I got seem acceptable, ruling out worn rings?
One last thing that I just noticed... I did the compression check last night, came home tonight and started getting into the bypass covers. As I'm ripping into it, I notice that the starter hadn't disengaged from the flywheel. I have absolutely no clue if that's just the result of me cranking on it without starting it while checking the compression? Or is it possible I just ripped half my engine apart for something as stupid as a stuck starter? I didn't really notice any odd noises while it was running, but I really wasn't paying that close of attention either.
So, there it is. Hopefully the hive-mind of iBoats can offer some insight. (And if any of you are from the Minneapolis/St Paul area, and have some good ideas, I'll ply you with beer and home-cooked steak dinner if you wanna come help me get this running!)
Lastly... My warning to others, when they say "disconnect the battery"... DISCONNECT THE BATTERY ya doofus! See attached pic. This was the wire that runs from the output of the rectifier/regulator down to the start solenoid. This could have ended way worse!
Backstory, I bought the boat about 2 years ago as "a good runner". Well, long story short, it's not a good runner. Backstory on me, I consider myself reasonably handy, know my way around a garage a bit, but by no means consider myself a pro. I don't have a ton of experience on outboards.
On to the boat:
Last year I was able to get it idle reasonably well, it would idle fairly well, but it was super rough and would occasionally stall. First couple trips this year it was about the same, but now last weekend it just wouldn't idle to save its life. I fiddled with the low-speed jets to no avail.
So last year this is what I did:
New plugs (the ones in the attachments have about a full Minnesota season on them, probably less than 20 hrs.)
New stator and pickup. (Replaced more because the insulation was falling off them)
Replaced any other questionable wiring.
New rectifier. (Wasn't getting a tach signal)
Rebuilt carbs, good cleaning, new needle/seat/gaskets.
Checked timing, this SEEMED ok, but I was struggling to get a consistent reading.
New fuel line, tank to motor, new bulb.
At the end of the season I winterized with sea-foam, the run for a half-hour with a heavy sea-foam mix, then spray sea-foam in the carbs until it dies trick. Bit of sta-bil in 5 gallons of fresh gas.
Prior to the new season, the only thing I did was add a new fuel tank, went from portable to permanent (not sure if that's relevant.)
Beginning of the season, started right up on the muffs. Idled reasonably well, same as last season, rough and would occasionally stall. Topped off the 14 gal tank, and off to the lake. No change in idle quality, but it still ran strong once underway. Then this last weekend, I couldn't get it to idle to save my life.
Cold start seems OK. Set the throttle open a smidge, choke it, starts right up. Let it run around 1500 RPM for a couple minutes. When I pull it back to idle it drops to around 900 RPM, chugs for a bit, then it sputters and dies. Once it's hot, it'll fire right back up, idle for a beat or two, then chugga chugga chugga, dead.
Getting into gear is a fun exercise! But once underway it'll putter around at 1100-1500 RPM just fine, and at wide open it'll get to just over 5000 RPM and push the boat around at 35 MPH on the GPS.
After it started acting up this year I dug into it again:
Compression checked: 130,130,130,120
Checked the bleed hose/check valve (I disconnected the hose at the top, I was able to suck but not blow)
Verified float height was 11/16" (I wasn't able to get a real good measurement, no ruler thin enough, so I'd call it 11/16 +/- 1/16)
Re-set low speed jets, with no success.
Attached are what the spark plugs look like after about probably 20-30 hours.
In a prior thread it was mentioned that the bleed inserts tend to fall out, and that can cause bad idle. I pulled the bypass covers off, see attached pic. I don't know what these are supposed to look like, but to my untrained eye I don't see any sort of nylon/plastic insert in any of the three holes. Prior wisdom suggested an 8/32 set-screw with an .040 hole in it. These holes look to be about the size that you'd shove an 8/32 screw into...
Also in a prior thread, thank you racerone, it was mentioned to "Look at reed valves , labyrinth seal grooves in the reed blocks, bottom crankshaft seals, piston and ring wear, bleed inserts..." From what I understand with this motor, the reed blocks are hidden underneath the bottom of the crank shaft? And others have suggested that the reeds in this particular unit are fairly resilient. Those last suggestions (other than the bleed inserts) would require some serious tear-down that I'm hoping to avoid. Are there any checks I can do to test these that don't involve removing the powerhead? From what I've read about compression testing, the numbers I got seem acceptable, ruling out worn rings?
One last thing that I just noticed... I did the compression check last night, came home tonight and started getting into the bypass covers. As I'm ripping into it, I notice that the starter hadn't disengaged from the flywheel. I have absolutely no clue if that's just the result of me cranking on it without starting it while checking the compression? Or is it possible I just ripped half my engine apart for something as stupid as a stuck starter? I didn't really notice any odd noises while it was running, but I really wasn't paying that close of attention either.
So, there it is. Hopefully the hive-mind of iBoats can offer some insight. (And if any of you are from the Minneapolis/St Paul area, and have some good ideas, I'll ply you with beer and home-cooked steak dinner if you wanna come help me get this running!)
Lastly... My warning to others, when they say "disconnect the battery"... DISCONNECT THE BATTERY ya doofus! See attached pic. This was the wire that runs from the output of the rectifier/regulator down to the start solenoid. This could have ended way worse!