Hello all, I'm assisting my father in law with his boat and have run across an issue that has stumped us. Here are the boat details. It's a 1984 Anna Capri 24ft. It has the Volvo Penta outdrive with a GM 350 engine. The cooling setup is the engine is a closed loop, cooled with fresh water/antifreeze. The small reservoir/heat exchanger is cooled with sea water and emptied out the exhaust manifolds.
A couple weeks ago we took the boat and first experienced the problem. We had driven about 5 miles and anchored, no overheating. We fished for 45 minutes or so and then fired up the engine. Within a couple minutes of moving the temperature went hot, completely to the limit! I opened the engine cover and the there was antifreeze spewing from the radiator cap. We managed to get it home by removing the cap and using all the bottled water we had to refill it.
The boat sat, and the following weekend my father in law returned and replace the thermostat, just thinking that could have been it. This time he idled in the slip for 30 minutes or so, with a normal temp, and then took it out. After about a 1/4 mile it started overheating again and he returned to slip.
This week I am in town again and went to go look at a few things. We clean the lower unit thinking the water intake could have been blocked. I took the water hose off of the Raw water pump and verified the impeller was in there and felt intact. I then started the engine and the raw water pump did in fact push water out, so I assumed it was working. Next I replaced the radiator cap as the old cap didn't seal and was not holding pressure in the pressurized loop.
After all the above, we idled at the slip about 30 minutes and the temp was great. We then left slip and drove about 40 minutes up and down the water way without any change, temp is right in the middle (no numeric markers on the temp gauge). After much running around we noticed the temp finally started steadily creeping up. It took about 4 minutes to go from normal to Hot, but luckily we were right by the slip and pulled in.
At this point, we suspect it's a water flow issue, but are not sure if it's on the closed loop side or the raw water side. Could the raw water pump be intermittently failing? I've seen a lot of water pumps fail on car engines, and most times they seem to just die! Could it be the water pump for the engine cooling (closed loop) water? Any and all suggestions would be welcome. Thank you.
A couple weeks ago we took the boat and first experienced the problem. We had driven about 5 miles and anchored, no overheating. We fished for 45 minutes or so and then fired up the engine. Within a couple minutes of moving the temperature went hot, completely to the limit! I opened the engine cover and the there was antifreeze spewing from the radiator cap. We managed to get it home by removing the cap and using all the bottled water we had to refill it.
The boat sat, and the following weekend my father in law returned and replace the thermostat, just thinking that could have been it. This time he idled in the slip for 30 minutes or so, with a normal temp, and then took it out. After about a 1/4 mile it started overheating again and he returned to slip.
This week I am in town again and went to go look at a few things. We clean the lower unit thinking the water intake could have been blocked. I took the water hose off of the Raw water pump and verified the impeller was in there and felt intact. I then started the engine and the raw water pump did in fact push water out, so I assumed it was working. Next I replaced the radiator cap as the old cap didn't seal and was not holding pressure in the pressurized loop.
After all the above, we idled at the slip about 30 minutes and the temp was great. We then left slip and drove about 40 minutes up and down the water way without any change, temp is right in the middle (no numeric markers on the temp gauge). After much running around we noticed the temp finally started steadily creeping up. It took about 4 minutes to go from normal to Hot, but luckily we were right by the slip and pulled in.
At this point, we suspect it's a water flow issue, but are not sure if it's on the closed loop side or the raw water side. Could the raw water pump be intermittently failing? I've seen a lot of water pumps fail on car engines, and most times they seem to just die! Could it be the water pump for the engine cooling (closed loop) water? Any and all suggestions would be welcome. Thank you.
