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Getting very good pressureDetermine whether you’re bringing adequate cooling water into the system.
First thing to check is condition or functionality of your raw water pump.
You can disconnect the hose coming from your transom from the thermostat housing, have someone hold it upright and start the engine.
You should see a good 3” plume of water coming out. Hold the hose at the same level as where it was connected.
It could be many things, but this is where to start.
Great advice to remove and inspect all hoses . I recently changed all my cooling hoses because inspection proved deterioration due to age and restrictions caused by deposits. Although I was not overheating on my raw water cooled 7.4 running at 145 I had a leak develop on my lower port exhaust boot on removal I was able to rip it completely open along the seam. .inspection showed more heat damage to it and the upper exhaust boot as well as the shutter valve located at the y tube. Also the largest hose I'm the circulation pump proved the cooled steel insert to be displaced restricting flow . After replacing every hose and the exhaust tubes and shutters . I did an acidic flush of my cooling system . Now my portside riser is cool it had been a little hotter. Another thing I did was clean up the little ball apparatus that is in the t stat housing. . I recommend changing old hoses they may look ok but be soft which can cause slight collapsing and restrict flow. Others may have cracks that you can't see easily until you manually bend them at which time you realise they were a failure waiting to happen . My old boat gad been well maintained but an often overlooked job is hose replacement . Recconended interval by merc for this is 3 years . I recconend ordering onlune agead of time to save aboutv50 percent of chandlers price . Total costs for my hoses shutters and exhaust tubes was about 500 so not cheap but I feel good I'm not going to wreck my motor or family boating time over lax maintenancei have extensive knowledge of 6.2 cooling.. was a nightmare on mine with overheating...
found the prior owner servicing left a piece of broken impeller that was wedged in the fuel cooler exchanger inline... best bet is to take the hoses off and literally look through.. i did mine 3 times before i found the piece... once removed, cooled and stays at 165ish
Thank You!!!Great advice to remove and inspect all hoses . I recently changed all my cooling hoses because inspection proved deterioration due to age and restrictions caused by deposits. Although I was not overheating on my raw water cooled 7.4 running at 145 I had a leak develop on my lower port exhaust boot on removal I was able to rip it completely open along the seam. .inspection showed more heat damage to it and the upper exhaust boot as well as the shutter valve located at the y tube. Also the largest hose I'm the circulation pump proved the cooled steel insert to be displaced restricting flow . After replacing every hose and the exhaust tubes and shutters . I did an acidic flush of my cooling system . Now my portside riser is cool it had been a little hotter. Another thing I did was clean up the little ball apparatus that is in the t stat housing. . I recommend changing old hoses they may look ok but be soft which can cause slight collapsing and restrict flow. Others may have cracks that you can't see easily until you manually bend them at which time you realise they were a failure waiting to happen . My old boat gad been well maintained but an often overlooked job is hose replacement . Recconended interval by merc for this is 3 years . I recconend ordering onlune agead of time to save aboutv50 percent of chandlers price . Total costs for my hoses shutters and exhaust tubes was about 500 so not cheap but I feel good I'm not going to wreck my motor or family boating time over lax maintenance
ThanksGreat advice to remove and inspect all hoses . I recently changed all my cooling hoses because inspection proved deterioration due to age and restrictions caused by deposits. Although I was not overheating on my raw water cooled 7.4 running at 145 I had a leak develop on my lower port exhaust boot on removal I was able to rip it completely open along the seam. .inspection showed more heat damage to it and the upper exhaust boot as well as the shutter valve located at the y tube. Also the largest hose I'm the circulation pump proved the cooled steel insert to be displaced restricting flow . After replacing every hose and the exhaust tubes and shutters . I did an acidic flush of my cooling system . Now my portside riser is cool it had been a little hotter. Another thing I did was clean up the little ball apparatus that is in the t stat housing. . I recommend changing old hoses they may look ok but be soft which can cause slight collapsing and restrict flow. Others may have cracks that you can't see easily until you manually bend them at which time you realise they were a failure waiting to happen . My old boat gad been well maintained but an often overlooked job is hose replacement . Recconended interval by merc for this is 3 years . I recconend ordering onlune agead of time to save aboutv50 percent of chandlers price . Total costs for my hoses shutters and exhaust tubes was about 500 so not cheap but I feel good I'm not going to wreck my motor or family boating time over lax maintenance