Temperature jumps from 125 -200 and back quickly

Rotorpilot1969

Seaman Apprentice
Joined
Sep 8, 2012
Messages
35
I have a 1999 ebb tide with merc 5.0 and alpha one gen two. I just did a complete bellows make over and replaced the drive impeller. Last year when I parked the boat it was running fine. This spring I decided to do the impeller, gimbal and ujoints because they hadn't been done that I knew of. Yesterday I hooked to the water muffs and the boat got a little hot and I shut it off thinking not enough water pressure. So today I took to the lake and left on trailer and allowed boat to come up to temp and it reminded at 150 for a long time and thinking it was fine we launched the boat and I took off across the lake on plane for several miles at 2/3 throttle. Boat shifted and ran perfectly with no unusual issue. After 3 miles I throttled down easily and came to a idle and the boat started alarming and jumped up to near 200 and I took off to cool down the engine and it then dropped down to 125 (never seen below 150 warm ) and then would rise back to 150 or so as it always ran and all was good until I throttled down again and the issue repeated itself. I removed the small left facing engine thermostat hose and started engine and it had a really good water flow. I did no other trouble shooting because it was getting dark and just loaded boat and came home. I don't think it's my thermostat because I believe it would be a opposite heating issue. Could the pickup tube in the lower unit be off set or even have a hole causing a vacuum ? Could my engine water pump be faulty? I just don't think I did anything wrong. My old impeller was in excellent condition so I don't see a obstruction in the system causing this problem. I replaced the water tube in the gimbal housing and can't see it being twisted. I just wonder if it had a blockage in it because I never looked in the tube. It was new. All help appreciated.
 

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Re: Temperature jumps from 125 -200 and back quickly

Did you use alignment pins when re-assembling the pump hosing to the drive? And what about the vee seal on the top of the pump housing? Set that with the proper tool?

Chris.......
 

Rotorpilot1969

Seaman Apprentice
Joined
Sep 8, 2012
Messages
35
Re: Temperature jumps from 125 -200 and back quickly

Did you use alignment pins when re-assembling the pump hosing to the drive? And what about the vee seal on the top of the pump housing? Set that with the proper tool?

Chris.......

I was able to fix, I think I knocked the tube loose when I put back together. Runs solid on 150 now thanks for reply
 
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