GT-40 idle overheat.... sometimes

[Chexi]

Most were right in the pump. I have to confess that I have not found the others. The boat ran fine after I replaced it and never got over 170 degrees. My limited time with that boat (in Iowa) means I did not have time to do a thorough check yet.

[Joesboatn]

This is how i found it easiest to put in the thermostat. The hoses going directly into the top of the thermostat housing are on there really tight so just leave those on. One of those hoses is only about 12 inches long going just across to the other side of the engine. Undo that hose clamp and pop the hose off. Undo the two allen bolts from the top of the thermo. Make sure your allen wrench is a good tight fit in the bolts you dont want to stip those heads. Once those bolts are out and the hose is disconnected from the other side the entire top housing will swing off with the hoses still attached. Pull out your old stat clean off the old gasket off your housing and install. Putting in my impeller I submerged my housing into a bucket of soapy water and used that for lubrication to get my new impeller in the housing. Also when I put the oring in for the impeller I placed a real thin coat of silicone on the o ring. If anyone has anything to add Id love to hear.

[DanielC]

I like to polish the side of the brass plate that rides against the inpeller with some very fine sandpaper when I have the pump apart. If the plate gets some deep grooves in it, turn it over, and polish that side, and use it.

[natetnc]

ok, impeller was shredded, it looked like i hit it with a lawn mower a few times, will post pic later. impeller did not come with O ring, my old one seemed to be in pretty good condition so i put it back in there. fine sanded the areas mentioned and put it back together with a little oil for lubrication. getting the pump in and out of the bracket was rather difficult but i managed. to get it back in i had to dissconnect the a hose going up the front of the engine, a lot of water came out, not really sure how much, maybe a qtr to half gallon. will it be ok to start it without this water? will replace t-stat tomorrow.

[WakeSlayer]

Yup, it will prime the system again when you start it in the water. Keep an eye on your temp gauge the frist few minutes you have it running.

[natetnc]

took it out on the lake this weekend, made a run to the area we usually ride in, noticed it was running cool all the way out there (~ 130deg). didn't change the t-stat because i didn't have the a-wrench it required, thought it was sticking open. got to the area and noticed the carpet getting a little wet, opened the hood and one of the hoses had come partially off shooting water into the bay, almost filled it up. when i tightened the hose back on the U piece located right behind the w-pump pulley it wasn't all the way on, it flared the end of the hose so there was no way it was staying on. after a few more trial and errors we got the hose back on correctly and it ran perfectly holding temp a hair below 160 all day.

one guy i was with said you should only tighten the hose clamps with a screw driver to keep from over tightening them and messing up the hoses. somewhere on this forum i read a post that suggested using a hexhead to tighten. the hose blew off again after a screw driver tightening so i short wrenched a small ratchet to tighten up the next time..... it held. what do you guys use to tighten your hose clamps?

thanks for all the help, saved me a trip to the boat shop and most importantly $

[Chexi]

I've used both a screwdriver and a socket wrench. Just do not crank too hard with a wrench and check for leaks periodically.

[DanielC]

I use a 5/16 (8mm) socket on a nut driver handle. I also use a small 1/4 drive ratchet in hard to reach places.

[Watty]

The thermostat housing is next housing after the water pump and it should have outlets going into the exhuast manifolds. It is pretty easy to get the housing off and remove the thermostat. The hard part is removing the old gasket which took me a couple of hours using brake cleaner and a gasket scrapper. Once the old gasket is removed then just throw the new gasket on and drop in the thermostat and you are good to go. I would also check your raw water strainer because it sounds like you may have a leak there if you overheat at idle. Typically once you get moving there is enough pressure in the system that it clears up a small leak but if overheating at idle then that would be the first thing I would check. Good luck and most of this stuff is pretty simple especially on a DD since the engine is pretty easy to get to.

[live2ski]

Without Thermostat

Do any of you know what would happen if you ran without the thermostat?
If a thermostat fails does it fail open or closed?

I replaced the impeller at the start of this season and ran great until the other day. We were trolling around the lake when I noticed the temp light was on. We head back to the dock at a faster speed and the temp came down alittle. I cleaned out the intake screen and cup (it wasn't too bad), I haven't checked the impeller or the stat yet because I don't have the replacement parts.

Thanks,
Drew