This is a 1981 Mercruiser 898, GM 305, 2-barrel Rochester carb and Mallory distributor, Pertronix Ignitor II points conversion, Pertronix Flamethrower II coil, MR outdrive on a Sea Ray V197. Ignitor module is powered through a relay and getting direct battery voltage when key is in "Run" position. Only non-ethanol fuel from marina.
Have had boat 4 years, and it's been great and reliable up until last few weeks of this season. I've been at this for about 10 days now, and I just can't figure out what is wrong. Local marinas have a long wait list to look at anything, and the place I used to go is under new management and won't work on anything older than 2000. I'm getting desperate, with the season quickly coming to an end. Any help is much much appreciated.
I *think* I've got a spark issue, but I'm not experienced enough to know for sure. I have what looks like good spark coming from ignition coil, but I don't have good spark at the plugs.
To baseline, this is what I'm perceiving as good spark coming from the ignition coil and bad spark at the plugs:
Coil test showing good spark from coil: Attached, and at
Spark test showing irregular spark at plug: Attached, and at
Distributor spinning when engine cranks: Attached, and at
Possible hint: While still not running anywhere near correctly, it seems to be a little closer to running, and might run for 30 seconds or so, on the first try of the day. After that, it will rarely catch. I can pump the accelerator pump and see fuel come out, let it sit for a few hours, but no change.
I had no reason to look for electrical problems other than process of elimination.
This is the chain of events, which I understand may be tedious to read through.
No modifications this season or last. Boat was running great for months. Once in a while would bog down when accelerating, usually after boat had been running, then stopped, then loaded up with passengers/gear or fuel. Would work itself out after a minute or so and then run fine. I presumed a carb rebuild was in my future. In the mean time I changed plugs and wires.
Some weeks later, boat would only start if I caught it just right, with a lot of throttle. Had been running great and almost daily right up until then. Once started, it would run fine. This happened for maybe three outings. On the last outing, I got a rope caught up in the alternator and shredded the belt. Alternator seemed unharmed, I replaced belt in driveway, boat ran fine in driveway (on muffs), but then had no power and would eventually stall when in water. After some diagnosis found that one-year old ignition switch had failed, and had no continuity in "Run" position. Replaced switch, boat started right up, ran fine in driveway, put it in the water, and then same thing: no power and would quickly stall and die.
Presumed it was time to rebuild carb, and did so. Didn't find anything wrong or dirty or blocked, but rebuilt it anyways. Boat would start up fine in driveway, but then had no power and would eventually stall when in water. Rebuilt carb again, and did find that I had not properly set float, but was meticulous this time around and everything set correctly. Verified there is fuel in fuel bowl. Verified that fuel squirts out from accelerator pump. No change in behavior.
Tried spraying starter fluid direct into carb while cranking. No change in behavior.
Since then, trying to find something wrong in the fuel/air/spark area, I have:
Replaced distributor cap. Old cap and rotor looked fine, but carbon button on distributor cap got stuck when I was testing resistance, so I replaced. Polished up rotor cap. No cracks or burns or anything that seemed bad. No change.
Found some poor connections when testing continuity and replaced power wire to coil. No change.
Verified distributor is well grounded, and there's no resistance between ignitor plate and battery negative or engine block.
Replaced coil. Went with Napa IC12 with external resistor. No change.
Pulled fuel lines, and tested fuel pump. Tests at 5 PSI. Tested that sufficient fuel volume is pumped out from fuel pump. Tested just fine.
Swapped in a Petronix ignitor I had on hand. No change, so reinstalled the Pertronix Ignitor II I've been running for past 3 years.
Pumped some fuel into a clear gas jar for inspection. Looks perfect. No water, no sediment or debris or cloudiness or anything other than clean fresh gas.
Tried to pull distributor for inspection, but there's insufficient clearance in the boat to fully remove. I reinstalled, with 8 degrees BTDC on cylinder 1. No change.
Replaced coil back to the original Petronix Flamethrower II. No change.
Tested resistance of wire from coil to distributor, which tested fine (500 ohms). Swapped in a new wire just in case, and no change.
The only thing I can think of that I have not tried is hooking up an external fuel tank, but at present I think spark is my issue and I have verified fuel and fuel delivery looks good.
Changing distributor would be very difficult, as there's no clearance to remove. Would involve basically pulling the engine from what I can see. I don't want to go there unless there's good reason to think it is a faulty distributor.
If reading this, I would assume the poster unnecessarily rebuilt the carb and screwed it up, but I've checked and rechecked my work and I can't see any mistake.
I'm thinking that something is getting warmed up in the distributor and somehow preventing regular spark out the distributor cap, but I can't think of what that might be.
Thanks for any thought or comments,
Jim
Have had boat 4 years, and it's been great and reliable up until last few weeks of this season. I've been at this for about 10 days now, and I just can't figure out what is wrong. Local marinas have a long wait list to look at anything, and the place I used to go is under new management and won't work on anything older than 2000. I'm getting desperate, with the season quickly coming to an end. Any help is much much appreciated.
I *think* I've got a spark issue, but I'm not experienced enough to know for sure. I have what looks like good spark coming from ignition coil, but I don't have good spark at the plugs.
To baseline, this is what I'm perceiving as good spark coming from the ignition coil and bad spark at the plugs:
Coil test showing good spark from coil: Attached, and at
Possible hint: While still not running anywhere near correctly, it seems to be a little closer to running, and might run for 30 seconds or so, on the first try of the day. After that, it will rarely catch. I can pump the accelerator pump and see fuel come out, let it sit for a few hours, but no change.
I had no reason to look for electrical problems other than process of elimination.
This is the chain of events, which I understand may be tedious to read through.
No modifications this season or last. Boat was running great for months. Once in a while would bog down when accelerating, usually after boat had been running, then stopped, then loaded up with passengers/gear or fuel. Would work itself out after a minute or so and then run fine. I presumed a carb rebuild was in my future. In the mean time I changed plugs and wires.
Some weeks later, boat would only start if I caught it just right, with a lot of throttle. Had been running great and almost daily right up until then. Once started, it would run fine. This happened for maybe three outings. On the last outing, I got a rope caught up in the alternator and shredded the belt. Alternator seemed unharmed, I replaced belt in driveway, boat ran fine in driveway (on muffs), but then had no power and would eventually stall when in water. After some diagnosis found that one-year old ignition switch had failed, and had no continuity in "Run" position. Replaced switch, boat started right up, ran fine in driveway, put it in the water, and then same thing: no power and would quickly stall and die.
Presumed it was time to rebuild carb, and did so. Didn't find anything wrong or dirty or blocked, but rebuilt it anyways. Boat would start up fine in driveway, but then had no power and would eventually stall when in water. Rebuilt carb again, and did find that I had not properly set float, but was meticulous this time around and everything set correctly. Verified there is fuel in fuel bowl. Verified that fuel squirts out from accelerator pump. No change in behavior.
Tried spraying starter fluid direct into carb while cranking. No change in behavior.
Since then, trying to find something wrong in the fuel/air/spark area, I have:
Replaced distributor cap. Old cap and rotor looked fine, but carbon button on distributor cap got stuck when I was testing resistance, so I replaced. Polished up rotor cap. No cracks or burns or anything that seemed bad. No change.
Found some poor connections when testing continuity and replaced power wire to coil. No change.
Verified distributor is well grounded, and there's no resistance between ignitor plate and battery negative or engine block.
Replaced coil. Went with Napa IC12 with external resistor. No change.
Pulled fuel lines, and tested fuel pump. Tests at 5 PSI. Tested that sufficient fuel volume is pumped out from fuel pump. Tested just fine.
Swapped in a Petronix ignitor I had on hand. No change, so reinstalled the Pertronix Ignitor II I've been running for past 3 years.
Pumped some fuel into a clear gas jar for inspection. Looks perfect. No water, no sediment or debris or cloudiness or anything other than clean fresh gas.
Tried to pull distributor for inspection, but there's insufficient clearance in the boat to fully remove. I reinstalled, with 8 degrees BTDC on cylinder 1. No change.
Replaced coil back to the original Petronix Flamethrower II. No change.
Tested resistance of wire from coil to distributor, which tested fine (500 ohms). Swapped in a new wire just in case, and no change.
The only thing I can think of that I have not tried is hooking up an external fuel tank, but at present I think spark is my issue and I have verified fuel and fuel delivery looks good.
Changing distributor would be very difficult, as there's no clearance to remove. Would involve basically pulling the engine from what I can see. I don't want to go there unless there's good reason to think it is a faulty distributor.
If reading this, I would assume the poster unnecessarily rebuilt the carb and screwed it up, but I've checked and rechecked my work and I can't see any mistake.
I'm thinking that something is getting warmed up in the distributor and somehow preventing regular spark out the distributor cap, but I can't think of what that might be.
Thanks for any thought or comments,
Jim
