Hi!
Great forum, I did some searching but havn't found the solution yet...
Work for a company that runs a fleet of (larger) boats, all diesel. A few years ago the company bought a Merc 5.7LX I/O powered 23' Doral for a runabout. I'm not sure offhand what drive it has on it.
The previous owner overheated the original engine in 2001. A new engine was installed at this time. Four barrel Webber/Edelbrock carb, Tbolt 5 ignition, raw water cooled. Current engine has 550~600 hours on it.
The boat went in the water about a month ago and people have been complaining about it dying on them since.
The first person to look at it replaced the plugs, plug wires, distributor cap, and the ignition sensor (with no real improvement) before passing it on to me.
I started playing with it about a week ago:
1) Boat started perfectly, idled perfectly, but spluttered, backfired and died after 1~3mins when you open it up above ~1500rpm.
2) Notice the temp didn't get above 120F so I replaced the t-stat (with a 160F unit).
3) Engine then ran 160F ~ 165F but still spluttered, backfired and died after 1~3mins when you tried to open it up above ~1500rpm (so I'm thinking timing or lean mixture/fuel starvation).
4) Check timing - OK.
5) Check fuel pressure and tank vent - OK.
6) Remove carb and inspect - full of crap so send carb out to be rebuilt.
7) Install rebuilt carb - set idle at ~750rpm and idle A/F adjustment screws to ~2.5 turns out. Engine now runs perfectly at all speeds, but dies after 20~60mins (depending on load/speed). It will kind of splutter for a few seconds before shutting down (so now I'm thinking ignition).
8) After waiting for 2~5mins the engine will start right up again and run fine for another 5~30mins (depending on load/speed).
9) Pulled tach lead off of coil - no difference.
10) Bypassed emergency stop switch - no difference.
And that's pretty much where I am now.
I noticed that the coil was pretty hot after running for a while so I have a new coil on order.
Any other thoughts apart from the coil? Boat will run perfectly for 20-60mins (less time the harder you run it), splutter, and die. After waiting 2~5 mins the boat will start right up again.
I have thought about unplugging the wiring harness and jumping the ignition power (and starter) but havn't tried it yet.
My area of expertise lies in compression ignition engines so I'm starting to run out of ideas.
Great forum, I did some searching but havn't found the solution yet...
Work for a company that runs a fleet of (larger) boats, all diesel. A few years ago the company bought a Merc 5.7LX I/O powered 23' Doral for a runabout. I'm not sure offhand what drive it has on it.
The previous owner overheated the original engine in 2001. A new engine was installed at this time. Four barrel Webber/Edelbrock carb, Tbolt 5 ignition, raw water cooled. Current engine has 550~600 hours on it.
The boat went in the water about a month ago and people have been complaining about it dying on them since.
The first person to look at it replaced the plugs, plug wires, distributor cap, and the ignition sensor (with no real improvement) before passing it on to me.
I started playing with it about a week ago:
1) Boat started perfectly, idled perfectly, but spluttered, backfired and died after 1~3mins when you open it up above ~1500rpm.
2) Notice the temp didn't get above 120F so I replaced the t-stat (with a 160F unit).
3) Engine then ran 160F ~ 165F but still spluttered, backfired and died after 1~3mins when you tried to open it up above ~1500rpm (so I'm thinking timing or lean mixture/fuel starvation).
4) Check timing - OK.
5) Check fuel pressure and tank vent - OK.
6) Remove carb and inspect - full of crap so send carb out to be rebuilt.
7) Install rebuilt carb - set idle at ~750rpm and idle A/F adjustment screws to ~2.5 turns out. Engine now runs perfectly at all speeds, but dies after 20~60mins (depending on load/speed). It will kind of splutter for a few seconds before shutting down (so now I'm thinking ignition).
8) After waiting for 2~5mins the engine will start right up again and run fine for another 5~30mins (depending on load/speed).
9) Pulled tach lead off of coil - no difference.
10) Bypassed emergency stop switch - no difference.
And that's pretty much where I am now.
I noticed that the coil was pretty hot after running for a while so I have a new coil on order.
Any other thoughts apart from the coil? Boat will run perfectly for 20-60mins (less time the harder you run it), splutter, and die. After waiting 2~5 mins the boat will start right up again.
I have thought about unplugging the wiring harness and jumping the ignition power (and starter) but havn't tried it yet.
My area of expertise lies in compression ignition engines so I'm starting to run out of ideas.
