Greetings All!
Pretty new to forum but old to powerboats. I have an '85 Merc V6 (2 stroke of course) 150 Blackmax with a 21P Laser prop on an '85 Glastron SSV187. I have owned this package since 1992, and have changed the impeller every other year or so. Heres the problem; I am underway on plane around 3200RPM or higher for about 20 minutes, then the overheat alarm sounds. I immediately back down to idle and shut engine off within 5 seconds of alarm sounding. I wait a minute or so, restart engine and alarm is off. Alarm continues to not sound off at idle, in gear or out. Once underway again, alarm sounds after about 5-10 minutes of operation. I immediately reduce to idle RPM again but dont shut engine off this time and alarm ceases after about 5 seconds. Alarm continues to be silent while idling.
I have read several posts regarding overheating and corrective measures taken but there were some symptoms combinations I experience that I did not see anyone else had, so here are my observations.
Observations:
1) Telltale pee stream is much stronger than usual at off-idle RPMs (1500-WOT). Less intense at idle but consistent and not much weaker than at speed.
2) At beginning of day, little water coming from exhaust tubes (while cruising) and by end of day, NO water from exhaust tubes (while cruising - usually barfs lots of water) - now exhaust and steam or just exhaust.
3) Pee stream is hot to touch (not scalding but cant leave hand in it for more than 2-3 seconds).
4) Tops of heads can be touched for about 3 seconds before uncomfortable on your hand- hot, but not burn you hot.
5) Starts and runs perfectly at all times.
Other info and history:
1) Impeller and housing changed 12 months ago and has had about 8 hours use on it. Will be changing immediately as a precautionary measure.
2) T-stats changed about 7 years ago. Will change them immediately.
3) Poppet rebuilt about 7 years ago. Not sure if this is suspect or what to do with this.
4) I rebuilt engine about 8 years ago due to failed top crank bearing. Honed #1 and #2 cyls. #3,4,5,6 very light clean out hone. Stock pistons throughout.
5) Hourmeter says 100 hours since rebuild.
I think thats about it. Please let me know what you think!
THANKS-
Ron
Pretty new to forum but old to powerboats. I have an '85 Merc V6 (2 stroke of course) 150 Blackmax with a 21P Laser prop on an '85 Glastron SSV187. I have owned this package since 1992, and have changed the impeller every other year or so. Heres the problem; I am underway on plane around 3200RPM or higher for about 20 minutes, then the overheat alarm sounds. I immediately back down to idle and shut engine off within 5 seconds of alarm sounding. I wait a minute or so, restart engine and alarm is off. Alarm continues to not sound off at idle, in gear or out. Once underway again, alarm sounds after about 5-10 minutes of operation. I immediately reduce to idle RPM again but dont shut engine off this time and alarm ceases after about 5 seconds. Alarm continues to be silent while idling.
I have read several posts regarding overheating and corrective measures taken but there were some symptoms combinations I experience that I did not see anyone else had, so here are my observations.
Observations:
1) Telltale pee stream is much stronger than usual at off-idle RPMs (1500-WOT). Less intense at idle but consistent and not much weaker than at speed.
2) At beginning of day, little water coming from exhaust tubes (while cruising) and by end of day, NO water from exhaust tubes (while cruising - usually barfs lots of water) - now exhaust and steam or just exhaust.
3) Pee stream is hot to touch (not scalding but cant leave hand in it for more than 2-3 seconds).
4) Tops of heads can be touched for about 3 seconds before uncomfortable on your hand- hot, but not burn you hot.
5) Starts and runs perfectly at all times.
Other info and history:
1) Impeller and housing changed 12 months ago and has had about 8 hours use on it. Will be changing immediately as a precautionary measure.
2) T-stats changed about 7 years ago. Will change them immediately.
3) Poppet rebuilt about 7 years ago. Not sure if this is suspect or what to do with this.
4) I rebuilt engine about 8 years ago due to failed top crank bearing. Honed #1 and #2 cyls. #3,4,5,6 very light clean out hone. Stock pistons throughout.
5) Hourmeter says 100 hours since rebuild.
I think thats about it. Please let me know what you think!
THANKS-
Ron