ChadDouglas
06-15-2009, 11:49 AM
Hey guys, I've been lurking the forums for quite some time and really appreciate all the helpful info. However, now I've got to actually post because I am stuck!!!
We have a 1992 Supra Comp. It has 950 hours. Not a ton of problems, had to rebuild the tranny once but other than that it has been pretty simple.
So here's the dilemna: We were out on the lake this weekend cruising along at about 25mph and all of a sudden the boat made a loud clank and we yanked the throttle back. It didn't die, but sputtereed a little and then set to idle. After a minute or two we put it back in gear and we were able to drive it back to the dock at about 20mph with not problem. The next day was a similar situation. We used the boat for an entire hour at speeds from 20 to 30 mph with no problems. Then on our way back to the dock (And close to it htankfully) at about 25mph it did the exact same thingl it made a big "clank" noise and this time the boat died. However, once again I could start it right back up and drove it home at about 20mph with no problems.
After the repeat occurrance I went into trouble shooting mode. My first concern was the noise it made. It made me think it was the internals of the engine. However, I can sit at idle with the engine cover up and spool it up to 3800-4000rpms and it just hums. Not even a bit of vibration or leaking oil or any sign of engine damage. Additionally I've kept a close eye on the engine temp and oil pressure and they've been constant and at normal levels these past few days. So, in neutral I have not been able to get the engine to cut out. However, once I put the boat in gear and get up to about 25 or 30 mph it will go "clank" and the engine will either die or if I am quick on getting the throttle back to idle I can sometimes save it and get it to settle in at idle.
Here are the things I can thing it might be:
Transmission: possible, but it doesnt seem likely since it shifts perfectly to neutral, forward, and reverse without any issues. I can't think of a failure mode where something in the transmission would bind under load for just a second, killing the engine, and then work fine afterwards.....
Fuel: If the engine was completely and instantly starved of fuel it might go "clank" and act as it is. I pulled the fuel pump (which was replaced about 2 years ago) and it has great compression and is pumping just fine. I also checked the fuel filter and it was clean an no water or contamination was present so I dont think it's losing fuel.
Carb: not sure how this would cause the issue, but I thought I'd take a peak anyways. Looks clean and seems to be operating normally. We've had no carbuerator problems since it was rebuilt a few years back.
Spark: I'm thinking that the clank might be the result of the engine not recieving what it needs to continue running (air, spark, fuel) and it's just dying instantaneously and making a noise in the process. Could the problematic electronic ignition be failing intermittently and causing this issue? It sounds possible but I am a little curious as to why it would be so intermittent and I was not able to reproduce it unless the engine was under load.
Any thoughts? I don't really just want to start replacing things without some idea of what's wrong, but at this point we can't get too far from the dock so I am ready to start figuring this out! Thanks in advance for your help-
We have a 1992 Supra Comp. It has 950 hours. Not a ton of problems, had to rebuild the tranny once but other than that it has been pretty simple.
So here's the dilemna: We were out on the lake this weekend cruising along at about 25mph and all of a sudden the boat made a loud clank and we yanked the throttle back. It didn't die, but sputtereed a little and then set to idle. After a minute or two we put it back in gear and we were able to drive it back to the dock at about 20mph with not problem. The next day was a similar situation. We used the boat for an entire hour at speeds from 20 to 30 mph with no problems. Then on our way back to the dock (And close to it htankfully) at about 25mph it did the exact same thingl it made a big "clank" noise and this time the boat died. However, once again I could start it right back up and drove it home at about 20mph with no problems.
After the repeat occurrance I went into trouble shooting mode. My first concern was the noise it made. It made me think it was the internals of the engine. However, I can sit at idle with the engine cover up and spool it up to 3800-4000rpms and it just hums. Not even a bit of vibration or leaking oil or any sign of engine damage. Additionally I've kept a close eye on the engine temp and oil pressure and they've been constant and at normal levels these past few days. So, in neutral I have not been able to get the engine to cut out. However, once I put the boat in gear and get up to about 25 or 30 mph it will go "clank" and the engine will either die or if I am quick on getting the throttle back to idle I can sometimes save it and get it to settle in at idle.
Here are the things I can thing it might be:
Transmission: possible, but it doesnt seem likely since it shifts perfectly to neutral, forward, and reverse without any issues. I can't think of a failure mode where something in the transmission would bind under load for just a second, killing the engine, and then work fine afterwards.....
Fuel: If the engine was completely and instantly starved of fuel it might go "clank" and act as it is. I pulled the fuel pump (which was replaced about 2 years ago) and it has great compression and is pumping just fine. I also checked the fuel filter and it was clean an no water or contamination was present so I dont think it's losing fuel.
Carb: not sure how this would cause the issue, but I thought I'd take a peak anyways. Looks clean and seems to be operating normally. We've had no carbuerator problems since it was rebuilt a few years back.
Spark: I'm thinking that the clank might be the result of the engine not recieving what it needs to continue running (air, spark, fuel) and it's just dying instantaneously and making a noise in the process. Could the problematic electronic ignition be failing intermittently and causing this issue? It sounds possible but I am a little curious as to why it would be so intermittent and I was not able to reproduce it unless the engine was under load.
Any thoughts? I don't really just want to start replacing things without some idea of what's wrong, but at this point we can't get too far from the dock so I am ready to start figuring this out! Thanks in advance for your help-