Hi group, I am stuck with an overheating problem and hoping someone can suggest what to try next. I've had this boat since new and I've been doing all the maintenance.
It is a 2010 with a single VP 5.7 Gi-300-J (RAW water cooled), with a duoprop outdrive, with 326 hours. Always used in brackish water near Baltimore, Maryland.
Boat has never had any overheating issues until now. Last October I winterized it by draining the water, making sure to poke the drain holes in the block and manifolds, and then I added -100 antifreeze.
Risers and manifolds are two years old and I replaced them myself with Volvo ones. All cooling hoses also replaced two years ago. Outdrive removed for gimbal bearing replacement and inspection, was done at the beginning of the last season.
I checked the oil level and it looks fine, and the color is clear. Oil filler cap also has no signs of moisture in it.
Two weeks ago when I started de-winterizing, the engine started right up and had no issues. I used the flushing hose to cool it while on the trailer. Twice I let it run for a good 15 each time and the temp never went above 165 or so.
Four days ago I launched the boat, but by the time I got to my slip, the temp alarm went off. It got as high as 195 or so before I shut it off. I was in the middle of docking so I had no choice.
I haven't tested on plane yet but at idle it overheats every time. If I run it at 1000 RPMs for a few seconds, it makes no difference. I shut it off before it goes above 180 to avoid any engine damage.
I went ahead and first replaced the raw water pump with a backup I had on the boat. This pump had a new Volvo impeller. The impeller on the old one looked fine.
Then I replaced the thermostat with a new Volvo one I also had on the boat as a backup.
I tested the old one at home with boiling water and it was fine as well. It opened and closed without any issues.
These two changes made no difference. I also tested running the engine using the flushing hose and no difference either.
I used an IF and the area below the thermostat housing matches the gauge at about 195 degrees. Also the circulating pump hose gets very hot.
The raw water pump feels cool to the touch, and I can keep my hand on the risers for several seconds. They hit about 100 degrees or so. All the other hoses feel the same as the bay water temp.
I removed the serpentine belt to check the circulating pump and it turns freely and feels smooth. No play of any kind or leaks.
At this point I am not sure what to do next. I am tempted to replace the circulating pump but I figured I should ask here first in case I haven't tried something more obvious.
Thank you in advance for any help you can give me!
2010 VP 5.7 Gi-300-J Duoprop with 326 hours
It is a 2010 with a single VP 5.7 Gi-300-J (RAW water cooled), with a duoprop outdrive, with 326 hours. Always used in brackish water near Baltimore, Maryland.
Boat has never had any overheating issues until now. Last October I winterized it by draining the water, making sure to poke the drain holes in the block and manifolds, and then I added -100 antifreeze.
Risers and manifolds are two years old and I replaced them myself with Volvo ones. All cooling hoses also replaced two years ago. Outdrive removed for gimbal bearing replacement and inspection, was done at the beginning of the last season.
I checked the oil level and it looks fine, and the color is clear. Oil filler cap also has no signs of moisture in it.
Two weeks ago when I started de-winterizing, the engine started right up and had no issues. I used the flushing hose to cool it while on the trailer. Twice I let it run for a good 15 each time and the temp never went above 165 or so.
Four days ago I launched the boat, but by the time I got to my slip, the temp alarm went off. It got as high as 195 or so before I shut it off. I was in the middle of docking so I had no choice.
I haven't tested on plane yet but at idle it overheats every time. If I run it at 1000 RPMs for a few seconds, it makes no difference. I shut it off before it goes above 180 to avoid any engine damage.
I went ahead and first replaced the raw water pump with a backup I had on the boat. This pump had a new Volvo impeller. The impeller on the old one looked fine.
Then I replaced the thermostat with a new Volvo one I also had on the boat as a backup.
I tested the old one at home with boiling water and it was fine as well. It opened and closed without any issues.
These two changes made no difference. I also tested running the engine using the flushing hose and no difference either.
I used an IF and the area below the thermostat housing matches the gauge at about 195 degrees. Also the circulating pump hose gets very hot.
The raw water pump feels cool to the touch, and I can keep my hand on the risers for several seconds. They hit about 100 degrees or so. All the other hoses feel the same as the bay water temp.
I removed the serpentine belt to check the circulating pump and it turns freely and feels smooth. No play of any kind or leaks.
At this point I am not sure what to do next. I am tempted to replace the circulating pump but I figured I should ask here first in case I haven't tried something more obvious.
Thank you in advance for any help you can give me!
2010 VP 5.7 Gi-300-J Duoprop with 326 hours
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