Check New Thermostats

jeff behrens

Recruit
Joined
Apr 20, 2009
Messages
4
I just bought my first boat a month ago it definitly has turn into a project boat I had to do alot of repairs to get it in the water and not knowing much about boats i had to pay the repair shop for some but with this site i'm doing alot myself. Also this site has helped me from getting ripped off real bad at the shop so thanks alot to everyone that takes time to reply to these post
you are really helping people

About the thermostat my merc 260 was running hot the impeller was already changed so i checked the T-Stat it was shot so i replaced it with a new one. Still running hot so i checked the risers and manifolds because i saw alot of rust in t-stat housing but they must have been replaced recently because they were real clean no rust Decided to check new stat and it was worst than old one water began to boil before it started to open. So never again car or a boat will i throw a new one in without testing first Thanks again
 

Don S

Honorary Moderator Emeritus
Joined
Aug 31, 2004
Messages
62,321
Re: Check New Thermostats

There could be a number of things causing an overheat that you haven't even mentioned. Same results from 2 different thermostats would tell me that isn't the problem.
How about some details on your engine. likje YEAR, raw water or closed cooling system, does this happen in the water or on muffs or both, or ________________ Fill in the blank.
 

jeff behrens

Recruit
Joined
Apr 20, 2009
Messages
4
Re: Check New Thermostats

It's a 78 checkmate raw water and it happens with both but seems to drop temp a little on water with higher rmps never goes to red but real close i don't know any history on the boat that's part of the promblem i guess motor was rebuilt because 3 different machanics told me it's a real strong motor may be they replaced the exhaust manifolds then what else should i check thanks for the reply
 

captmello

Captain
Joined
Jun 30, 2008
Messages
3,826
Re: Check New Thermostats

Are the Risers overheating as well? Could be so many things.
 

jeff behrens

Recruit
Joined
Apr 20, 2009
Messages
4
Re: Check New Thermostats

The risers were pretty hot i could only hold my hand on them for a few seconds I pulled the risers and the three smaller ports on them were blocked up was able to clear them with screw driver and washed out with water hose Checked all the hoses and have reinstalled thermostat was'nt any rust chunks or anything under t-stat when i removed it (this time) Going to hook up new heat guage and sensor before i try it tommorrow it has the color guage now so i don't know the true temp just that it goes close to red line
 

Don S

Honorary Moderator Emeritus
Joined
Aug 31, 2004
Messages
62,321
Re: Check New Thermostats

It's a 78 checkmate raw water and it happens with both but seems to drop temp a little on water with higher rmps never goes to red but real close i don't know any history on the boat that's part of the promblem i guess motor was rebuilt because 3 different machanics told me it's a real strong motor may be they replaced the exhaust manifolds then what else should i check thanks for the reply

What make your boat is, doesn't mean anything in this forum. It's all about engine and drive.
Read this post.
http://forums.iboats.com/showthread.php?t=220416
 

jeff behrens

Recruit
Joined
Apr 20, 2009
Messages
4
Re: Check New Thermostats

It's a 78 with 350 motor as you can tell i know little about boats so i can't tell you what drive just say's mercruiser on it
 
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