"Last summer, with a boat full
"Last summer, with a boat full of people, I experienced the temp slowly climbing when first starting out from the mooring. I watched it until it was close to the "red" and then backed off to an idle. The temp gauge immediately pinned so I shut it down. Couldn't get it started from that point and had to be towed.
Water was in almost all the cylinders....blown head gasket I figure. Engine was 7 years old, had 400 hours, and is raw water cooled (salt water). It had new risers, 2 year old mainfolds, new water pump on block (Sierra Brand), & I always do at least the impellor each year, housing if it's corroded at all.
So replaced the motor with a rebuilt true 260 HP from a reputable local machine shop, (new impellor in the drive). Started it and have very similar results in the driveway with water hooked up to it. Remove the thermostat, no problem, runs cool as can be. I noticed the water pump (new last year) weeping from below so I replaced it and put the thermostat back in......now it runs fine.
I notice when putting the new and old water pump next to each other that the castings are similar but not the same. Has anyone experienced bad water pumps? I'd like to believe I've found the problem before I put the boat in the water. I took apart the housing and the impellor is not loose on the shaft. When the bearing goes in the water pump can air get in the hole just as water can get out? This would allow the pump to cavitate, explaining what happened."
"Last summer, with a boat full of people, I experienced the temp slowly climbing when first starting out from the mooring. I watched it until it was close to the "red" and then backed off to an idle. The temp gauge immediately pinned so I shut it down. Couldn't get it started from that point and had to be towed.
Water was in almost all the cylinders....blown head gasket I figure. Engine was 7 years old, had 400 hours, and is raw water cooled (salt water). It had new risers, 2 year old mainfolds, new water pump on block (Sierra Brand), & I always do at least the impellor each year, housing if it's corroded at all.
So replaced the motor with a rebuilt true 260 HP from a reputable local machine shop, (new impellor in the drive). Started it and have very similar results in the driveway with water hooked up to it. Remove the thermostat, no problem, runs cool as can be. I noticed the water pump (new last year) weeping from below so I replaced it and put the thermostat back in......now it runs fine.
I notice when putting the new and old water pump next to each other that the castings are similar but not the same. Has anyone experienced bad water pumps? I'd like to believe I've found the problem before I put the boat in the water. I took apart the housing and the impellor is not loose on the shaft. When the bearing goes in the water pump can air get in the hole just as water can get out? This would allow the pump to cavitate, explaining what happened."