Retired 40 year boat tech. Friend said can you help. 1998 Yam 150 V6 2 stroke. No power no idle.
"Ran" it on a hose (quotes because I could only keep it running by constantly poking the choke), pulled the plugs, water all over #5. Compression test was ok, damned if I can remember the numbers, but didn't alarm me. Checked fuel for water, good fuel, no water. Pulled the heads, no indication of HG leakage. Somewhere along the way, the other head (port) had been replaced and looked good. The one in question I cleaned and scraped and put it all back together with new HGs naturally. Checked spark, no spark #5. Swapped trigger leads, #5 trigger would fire the coil above (3) so grabbed a new coil. New plugs. Pulled and went thru the carbs, a little funky but I've seen way worse. Gave them a good ultrasonic cleaning anyway, checked the float heights as I reassembled, all look good to me. Now I go to run it, still it requires the choke to keep it running, so I get the owner out and have him sit at the motor and by hand keep the chokes closed enough to keep it running, while I go pull plug wires. Turns out this motor is running on only 2 cylinders (1&6). I'm fairly amazed I can keep it running on just those two. Still indication of water in 5. I ran another compression test, all 100-110. Now this seems low to me, and while I can't remember what it was before the heads came off, I have to believe it was better than this. Heads torqued retorqued, cylinders are in good shape. And here I am...
Motor of course now worth much, nothing in its present state. I just don't understand what I'm seeing here. A massive crankcase air leak? No external indication of leaking oil, at the block joint, for instance. All the drain hoses are intact. Sealing rings on the crankshaft, or something else internal? Reeds? Doesn't sneeze back thru carbs. Trigger under the flywheel or the ignition module? I've don't have a dva anymore to check output, but I've got spark.
Yes, I know, he needs a 4 stroke to get on with his boating life. We can give it to the local Yamaha folks, but he might as well put that money into replacement, if they'll even work on it. I'd just really like to understand what's happening with this thing. Thoughts, anyone? and thanks.
"Ran" it on a hose (quotes because I could only keep it running by constantly poking the choke), pulled the plugs, water all over #5. Compression test was ok, damned if I can remember the numbers, but didn't alarm me. Checked fuel for water, good fuel, no water. Pulled the heads, no indication of HG leakage. Somewhere along the way, the other head (port) had been replaced and looked good. The one in question I cleaned and scraped and put it all back together with new HGs naturally. Checked spark, no spark #5. Swapped trigger leads, #5 trigger would fire the coil above (3) so grabbed a new coil. New plugs. Pulled and went thru the carbs, a little funky but I've seen way worse. Gave them a good ultrasonic cleaning anyway, checked the float heights as I reassembled, all look good to me. Now I go to run it, still it requires the choke to keep it running, so I get the owner out and have him sit at the motor and by hand keep the chokes closed enough to keep it running, while I go pull plug wires. Turns out this motor is running on only 2 cylinders (1&6). I'm fairly amazed I can keep it running on just those two. Still indication of water in 5. I ran another compression test, all 100-110. Now this seems low to me, and while I can't remember what it was before the heads came off, I have to believe it was better than this. Heads torqued retorqued, cylinders are in good shape. And here I am...
Motor of course now worth much, nothing in its present state. I just don't understand what I'm seeing here. A massive crankcase air leak? No external indication of leaking oil, at the block joint, for instance. All the drain hoses are intact. Sealing rings on the crankshaft, or something else internal? Reeds? Doesn't sneeze back thru carbs. Trigger under the flywheel or the ignition module? I've don't have a dva anymore to check output, but I've got spark.
Yes, I know, he needs a 4 stroke to get on with his boating life. We can give it to the local Yamaha folks, but he might as well put that money into replacement, if they'll even work on it. I'd just really like to understand what's happening with this thing. Thoughts, anyone? and thanks.