After a year of on again, off again overheat issues I finally found my problem. Two years ago I had run through some sand while on the Ohio River. This sand was talcum powder fine and clogged the poppet valve cavity. I immediately got an overheat alarm at speed.
When I went to make the repair I went the full course- new thermostats, new poppet valve guts and new water pump. Flushed the entire water jacket and was certain everything was fine. The rest of the season was uneventful.
Last year the engine would occasionally overheat while at midrange RPM. It was fine at idle and up to 2,000 rpm. It was fine at anything above 4,000 rpm. However, running in the 2K-3K range would show a gradual rise in temperature until the alarm would kick on. It didn't do it everytime but more often than not it would. To add to the mix it would do it when I ran my 19 Tempest prop but never with my 13 Mirage. I could run all day, pull tubes, haul 7 people, etc with the Mirage and no issues- but put the Tempest on and boom, overheat alarm. I started thinking internal issues, cracked exhaust tuner, etc. It never was consistent enough to nail it down. I flushed numerous times looking for obstructions but never found anything. I knew the T-stats and poppet were new and clean, as was the impellor. Nothing made sense.
I took the boat out Saturday and within 2 minutes of leaving the dock the overheat alarm kicks on with the temp gauge at 250. I shut her off and limped back to the ramp, loaded and went home. I pulled the t-stat housings to look for pieces of an old impellor or other debris in the jackets. I was ready to pull heads and on a whim decided to test the t-stats. These stats were like new- clean and pretty. However, when I dunked them the port side stat opened properly as expected but the starboard side opened a bit and then the plate went crooked. I've NEVER seen this before and can't explain how it can happen. It's almost like the spring was weak on one side. The valve would actually get crooked by 1/4" and stick. I took the stat and tapped it on the counter and dunked it again. Now it worked fine until it cooled and I redunked it. It did the same thing except this time it only opened 1/8". So a new T-stat was not opening fully and causing my issue. The other contributing factors had very little to do with the overheat but they sure threw me off this. I replaced both t-stats last night and ran the boat- gauge was pegged at 140-150 and never moved from there so I am calling this FIXED.
I've never run into an intermittant T-stat issue before- new one for me.
UFM82
When I went to make the repair I went the full course- new thermostats, new poppet valve guts and new water pump. Flushed the entire water jacket and was certain everything was fine. The rest of the season was uneventful.
Last year the engine would occasionally overheat while at midrange RPM. It was fine at idle and up to 2,000 rpm. It was fine at anything above 4,000 rpm. However, running in the 2K-3K range would show a gradual rise in temperature until the alarm would kick on. It didn't do it everytime but more often than not it would. To add to the mix it would do it when I ran my 19 Tempest prop but never with my 13 Mirage. I could run all day, pull tubes, haul 7 people, etc with the Mirage and no issues- but put the Tempest on and boom, overheat alarm. I started thinking internal issues, cracked exhaust tuner, etc. It never was consistent enough to nail it down. I flushed numerous times looking for obstructions but never found anything. I knew the T-stats and poppet were new and clean, as was the impellor. Nothing made sense.
I took the boat out Saturday and within 2 minutes of leaving the dock the overheat alarm kicks on with the temp gauge at 250. I shut her off and limped back to the ramp, loaded and went home. I pulled the t-stat housings to look for pieces of an old impellor or other debris in the jackets. I was ready to pull heads and on a whim decided to test the t-stats. These stats were like new- clean and pretty. However, when I dunked them the port side stat opened properly as expected but the starboard side opened a bit and then the plate went crooked. I've NEVER seen this before and can't explain how it can happen. It's almost like the spring was weak on one side. The valve would actually get crooked by 1/4" and stick. I took the stat and tapped it on the counter and dunked it again. Now it worked fine until it cooled and I redunked it. It did the same thing except this time it only opened 1/8". So a new T-stat was not opening fully and causing my issue. The other contributing factors had very little to do with the overheat but they sure threw me off this. I replaced both t-stats last night and ran the boat- gauge was pegged at 140-150 and never moved from there so I am calling this FIXED.
I've never run into an intermittant T-stat issue before- new one for me.
UFM82