New thermastat now over heating

1994 5.0L ALPHA 1 GEN 2. Replaced the thermastat sleve oring and bottom gasket. I have the 6 hose housing. The reason for replacing the thermastat was the engine would not reach any temp obove 120. After a long hard run if you shut it off and let it sit a few minutes it might get up to 140. Hot soaking. After replacement on the muffs in drive way. The temp hits 200 and the temp alarm sounds and I shut down. Pulled the seapump hose off at the therm housing with engine running and it is pumping a good bit of water. The sleeve is in the right way as is the therm. What gives?

Re: New thermastat now over heating

Either your new stat doesn't work, or something is put together incorrectly.

Re: New thermastat now over heating

I pulled the therm cover off. therm is open but no water flowing. The lower pump is pumping. Is it possible that the block mounted pump has stopped pumping? Ran engine with therm cover off and no flow. Therm is open. Possible air pocket in block? Seems odd all worked good before, just ran cold. I used the shop vac to catch old gasket. Will pull the block pump off in the morning and check it.

Re: New thermastat now over heating

More info. I put the old therm in and ran it. Temp jumped to 200 but no alarm. Raised idle to 1500 rpm temp came down and stayed at 160-170 mark. Return to idle temp goes back up. Raise idle temp comes down. This is running on muffs in the drive way. Before when running on the lake, temp never gets above 130. Lower inpeller is 4 years old. Does this sound like impeller or block mounted pump? Thanks. I have the factory manual, what parts am I looking at replacing to do the impeller. Was planning to do a complete remove the out drive at the end of this season to do the trim senders and a bellows replacement. Should I just wait untill then? Thanks.

Re: New thermastat now over heating

You need a new raw water pump/impeller if it's 4 years old. It probably has only a few vanes left on it. Also if some vanes are broken off they're probably crammed up into the oil or power steering coolers...

Re: New thermastat now over heating

Yes I know. Kinda did not want to have to go into now but it is in need. Do they make a kit with all the parts needed or do you have to get them part by part? Thanks.

Re: New thermastat now over heating

Well,

here's an example. you can get them at every marine "store" etc OEM or aftermarket.


If your pump doesn't provide enough water flow at idle but pumps enough above idle, it's usually the impeller. They need to be changed every few years. (more often in salt water probably)

If you don't have a manual you probably should get one of those too!
http://www.boatfix.com/merc/Servmanl/14/14cover.pdf

10 FOOT INVADER said:

Yes I know. Kinda did not want to have to go into now but it is in need. Do they make a kit with all the parts needed or do you have to get them part by part? Thanks.

Click to expand...

Re: New thermastat now over heating

Thanks for the link. I will get the kit. Yes I have a manual. Just did not want to have to go into it until the end of the season. Thanks again.

Re: New thermastat now over heating

well you wont have to pull the drive to do the impellar just the lower unit.

IF you need to do bellows then Id do it now and avoid prolonging running with bad parts. The trim sender and limit switch could be done any time BUT if your pulling the drive to do the bellows then do that as well as it will allow you a lot more room and only to pull the drive one time.

You know what Don says:

Theres never enough time to do it the first time but you always have time to do it correctly a second time.

do it once and be done with it! Do it ona Firday afternoon and be ready to go to the lake on Saturday or do it on a Saturday and be ready to go to the lake on Sunday. You need to put some time in for maintnance and now is the time as its only JUNE not JULY 4th weekend!