STORY.
My 2002 Merc 115 ELPTO (0T464942) is giving me low-end rpm problems while running below around 1300 rpm down to idle. Freshwater use (no sand) lakes history.
Brought to 3 separate mechanics over the last 5 years, 2 were Merc techs in the Twin Cities (Mpls/St. Paul), and all said link/sync was good and that these motors just run cold-blooded. While I know 2+2's can be and are, it's not an answer, as I have a buddy who has the exact same engine, 1 year older, and it's smooth - night and day compared to mine. So it must be possible.
About 6 years ago I first noticed the issue, with occasional shaking/roughness at idle or slightly above in rpm, and it would always smooth out at about 1200 or 1300+ rpm, then nice and smooth up to 5200. I was beginning to get engine kills when shifting into forward or reverse and earlier this year began to get what sounds like occasional misfires throughout, even in the upper RPM range. It was always worse when the engine was warm, better when it was cold. The issue became progressively worse, so I decided to work through the 12 or so reasons that I've read could lead to the problem. Here's what I've done so far:
• Checked fuel and fuel system (found good with no water), added fuel water separator, replaced all engine fuel filters, and rebuilt fuel pump with Sierra kit.
• Cleaned (they were amazingly clean anyway) and rebuilt all 4 carbs (kept linkages intact), rebuilt carbs with OEM ss needles (had rubber-tipped aftermarket needles in there), verified throttle shutters closed and moving together with linkage arm (carefully eyed after reinstallation).
• Replaced reeds with Boyesen power reeds (for smoother idle, not really for power), and replaced all gaskets with new OEM - on intake reed blocks, intake manifolds, and both sides of cabs. Torqued with proper patterns and torque values.
• Backed out idle jets on carb 1 & 2 (one and a half full turns, or 3 half turns), plus 1/4 turn out rich for the Boyesen reeds (per instructions for those to keep from lean opping)
• Replaced bleed check valves with OEM and bleed hoses with OEM hose cut to proper lengths
• Tested trigger, stator, voltage regulator/rectifier, and found chared yellow wires to rectifier from stator - half of stator tested out of spec, replaced with CDI unit. Replaced rectifier with new. Replaced trigger with CDI unit while in there, just to be sure (though it tested barely within spec).
• Replaced CDM on Cyl 1 (read slightly out of spec) with new blue CDI unit.
• Replaced all 4 spark plugs with proper NGK's at .040" gap and tested spark with CDI tester - looked solid
Now it still does the same and is even slightly worse than before I started. I have "chattering" from 600-1200/1300 rpm, smoothing out after that and good when I transition to all 4 cyls, with nice power at WOT.
Where do I go next? I've seen a lot of discussions on 2+2's, but most don't write back about what did the trick or what the issue actually was. Link & sync, timing, scoured cyl walls, or something else? I have no TIMING MARKS or scale of any kind on my flywheel and haven't found a pointer or scribe for TDC. The manual shows there are timing marks for the 3 cyls, but nothing for 4 cyls. What's the best method after establishing TDC, count the cogs and work out the 360 deg picture? I think I'll need a white paint marker ...
Now the OEM service manual does state that one can adjust idle timing, which I've not yet attempted. Everyone here says that's not needed or even possible, and it's actually done only at Max cranking or 3000 rpm running, and no need to adjust idle for 2 deg BTDC. Right or wrong? I've checked the clearance between the roller and throttle cam, it's right at .020" with feeler gages not very tight (probably +.0005" or so), and the marks are centered with each other.
I'd REALLY love to be able to get this running right again for trolling. Any help is greatly appreciated. I will send updates on recommendations.
Best,
Rusty
My 2002 Merc 115 ELPTO (0T464942) is giving me low-end rpm problems while running below around 1300 rpm down to idle. Freshwater use (no sand) lakes history.
Brought to 3 separate mechanics over the last 5 years, 2 were Merc techs in the Twin Cities (Mpls/St. Paul), and all said link/sync was good and that these motors just run cold-blooded. While I know 2+2's can be and are, it's not an answer, as I have a buddy who has the exact same engine, 1 year older, and it's smooth - night and day compared to mine. So it must be possible.
About 6 years ago I first noticed the issue, with occasional shaking/roughness at idle or slightly above in rpm, and it would always smooth out at about 1200 or 1300+ rpm, then nice and smooth up to 5200. I was beginning to get engine kills when shifting into forward or reverse and earlier this year began to get what sounds like occasional misfires throughout, even in the upper RPM range. It was always worse when the engine was warm, better when it was cold. The issue became progressively worse, so I decided to work through the 12 or so reasons that I've read could lead to the problem. Here's what I've done so far:
• Checked fuel and fuel system (found good with no water), added fuel water separator, replaced all engine fuel filters, and rebuilt fuel pump with Sierra kit.
• Cleaned (they were amazingly clean anyway) and rebuilt all 4 carbs (kept linkages intact), rebuilt carbs with OEM ss needles (had rubber-tipped aftermarket needles in there), verified throttle shutters closed and moving together with linkage arm (carefully eyed after reinstallation).
• Replaced reeds with Boyesen power reeds (for smoother idle, not really for power), and replaced all gaskets with new OEM - on intake reed blocks, intake manifolds, and both sides of cabs. Torqued with proper patterns and torque values.
• Backed out idle jets on carb 1 & 2 (one and a half full turns, or 3 half turns), plus 1/4 turn out rich for the Boyesen reeds (per instructions for those to keep from lean opping)
• Replaced bleed check valves with OEM and bleed hoses with OEM hose cut to proper lengths
• Tested trigger, stator, voltage regulator/rectifier, and found chared yellow wires to rectifier from stator - half of stator tested out of spec, replaced with CDI unit. Replaced rectifier with new. Replaced trigger with CDI unit while in there, just to be sure (though it tested barely within spec).
• Replaced CDM on Cyl 1 (read slightly out of spec) with new blue CDI unit.
• Replaced all 4 spark plugs with proper NGK's at .040" gap and tested spark with CDI tester - looked solid
Now it still does the same and is even slightly worse than before I started. I have "chattering" from 600-1200/1300 rpm, smoothing out after that and good when I transition to all 4 cyls, with nice power at WOT.
Where do I go next? I've seen a lot of discussions on 2+2's, but most don't write back about what did the trick or what the issue actually was. Link & sync, timing, scoured cyl walls, or something else? I have no TIMING MARKS or scale of any kind on my flywheel and haven't found a pointer or scribe for TDC. The manual shows there are timing marks for the 3 cyls, but nothing for 4 cyls. What's the best method after establishing TDC, count the cogs and work out the 360 deg picture? I think I'll need a white paint marker ...
Now the OEM service manual does state that one can adjust idle timing, which I've not yet attempted. Everyone here says that's not needed or even possible, and it's actually done only at Max cranking or 3000 rpm running, and no need to adjust idle for 2 deg BTDC. Right or wrong? I've checked the clearance between the roller and throttle cam, it's right at .020" with feeler gages not very tight (probably +.0005" or so), and the marks are centered with each other.
I'd REALLY love to be able to get this running right again for trolling. Any help is greatly appreciated. I will send updates on recommendations.
Best,
Rusty
Last edited: