Over heat Johnson 115 Turbojet

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Posted by Clayton ( on June 26, 2005 at 21:52:40:

I have a 96 sunbird jetboat 14' with a Johnson 115 Turbojet. Problem is Overheat warning horn comes on after about 10 minutes. I did some troubleshooting today, this is what I came up with (mind you I am not a marine mechanic by any means) There is a good stream of water from the pisser at all rpm ranges, so I disconnected the water lines on the top of the heads and got a good stream of water from both the port and starboard sides. I am assuming that I have good water flow. The engine does not bog or seem to lose power after the horn sounds. So I disconnected the water temp switches one side at a time and with the starboard side disconnected and the port side connected the warning horn does not sound. So I am thinking maybe a bad switch on the starboard side. Does this sound reasonable to anyone here or is it possible I have a blockage in the starboard heads somewhere. If I have blockage how do you backflush this system. Also the water coming out or the pisser is very hot, almost hot enough to leave a nasty mark, is this a proper condition. The motor ran great all last season, this is a new problem for this year. I did have a temp problem a few years back and changed the thermostat for that one. I have not changed the fuel filter since I've had it (going on 4 years) Will low fuel pressure from a clogged filter affect the cooling? Thanx in advance for any help, Clay

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