Engine Temperature

C

corbeau

New Member
Aug 21, 2009
7
Sydney Australia
Boat Info
175 SPorts
Engines
135 Mercruiser Apha One
New member and relatively new to boating. Hope someone can help out.

Normally when running my MerCruiser 3.0L Alpha I Sterndrive normal operating temperature is around 170. Lately this has dropped to around 130 for some reason. Engine has been recently serviced and only 48 hours old. Any suggestions? Is this a problem?
 
G'Day Mate

I have the same motor and I run a temp of about 130 to 150. the guage only climbs to 170 if I switch off after a long hard run as I assume the water in the block will boil, so I now always let the motor idle for a minute or two.

I suspect your recient service might have changed the timing or replaced the water pump impeller or simillar, causing the temp to run lower.

See what the educated masses on this site have to say as well!!

Cheers
Mark
 
Thankes mark, thanks for the prompt response. Looks like nopt really an issue. You're right the impeller was replaced at the last service. Pretty sure that I have seen the temp still up around the 170 mark on some outings since then but can't be sure now. Just that the first mate noticed it last run and also commented. I guess running at a lower temperature isn't really a problem as performance etc all seem okay. As you noted, maybe some others can add something.

Thanks again and cheers!!
 
130 °F to 150 °F is too low. You should not experience any problems, but the engine will perform better, more efficiently, and last longer at the normal temperature.

Thermostat removal is a 2-bolt procedure. Put your old one in a pot on the stove to see where it first cracks open, and also verify it opens completely. I suspect your thermostat is not closing, or has some debris keeping it from closing.
 
Thanks springer3, will check that out. Last outing did run in to some weeds so maybe that could be the problem.

Thanks for the tip. Cheers!!
 
My 3.0 runs about 170-175 after warmed up. Find out if they opened the thermostat housing during the service. (Such as winterizing and pouring antifreese inside the thermostat housing). If they did, maybe they forgot to re-intall the thermostat or it has a piece of debri caught in it that is keeping it open partially.
 
I too agree you have a thermostat issue.

Normal gauge operation should be as such: You should see your coolant temp climb steadily till your coolant regulator opens at its rated temp. The gauge will typically feather back a tic and then stay rite close to rated temp. When running WOT for extended periods the coolant temp will typically creep up some as water flow from lower drive pump can't keep up with demand. Hope this helps you some. ...Ron
 
Mine also runs at 170 when warmed up. I use that number as my target to start timing my post outing 10 minute flush.
 
I have an 04 185Sport with 4.3l, it runs at 170 normally, it has dropped to the 130 range on several occasions, I have had to pull my thermostat several times and remove trash that had it stuck partially open and of course it would not warm up enough to open and release the trash, pull your thermostat and check it.
 
Yeah, me too ZZ13. Looks to be an open thremostat problem. Will be pulling iit out and checking this weekend.

Thanks for the reply.
 
Thanks midway, I appreciate your feedback. I will be doing just that this weekend. Small job I know but that thing called work gets in the way.

Will post results back to the forum. Thanks to all those that have replied. I appreciate your expert iinput.

Regards.
 
Bummer, now I am concerned about my temp, as it seems to stay steady around 150. It runs on dramaticaly after the ignition is turned off and the most likley culprit is high engin temp. Imagine if the temp was 170, it would run out of fuel before stopping.

Seriously, it gives me a reason to put the boat in the water this week end and check it out.

Any one that can point me in the direction of the thermostat? I would like to take it out to check first.

Cheers
 
Mark, my old SeaRay which was an 1987 3.0L ran at 140 and that was correct for it, 140 thermostat, not sure the age of yours but if it is closer to the 1987 era it may also have 140 thermostat, if it is later model it should run 170. I am not sure when they made the change from 140 to 170 so you may need to ask your dealer or mechanic to verify yours.
 
Last edited:
An update for all those who have helped.

I have just finished checking the thermostat and the plot thickens.

I found no junk in the thermostat, at least as far as I could check. Checked all the inlet and outlet hoses as well to make sure. Put everything back together, attached the muffs and started up again to see if maybe something had been dislodged anyway and problem solved. But NO, magic didn't happen.

This time the temp stayed just on 100 and went no further? I also noticed that water was only be discharged from one of the exhaust outlets on the sterndrive. Not sure if that's relevant.

I'm now thinking that maybe the impeller is damaged so didn't want to risk the engine anymore and switched off. I checked the thermostat again and it looked like water was getting to the inlet pipe though.

Looks like it going in for a $ervice by the pro$.

Thanks all for your contributions so far, I appreciate the suggestions and will post the results once resolved for the forum.

Cheers from Down Under.
 
As Springer said, a 2 bolt job. Easy. You may want to pick up a spare gasket at the local auto parts store. Pennies, but you'll be mad if you need it and don't have it. If you don't need it, keep it as a spare...
 
Sounds like $ervice Pro time is the thing to do. They most likely will want to revisit that thermostat area. The housings them selves can become corroded and bypass water around a closed thermostat. This should be obvious to your service pro.

If all is well with the regulator and housing, the accuracy of the temp gauge would be step 2. ...Ron
 
One thing you may check into is the wiring harness that routes threw the top of the motor from front to back which has the temp sending wire in it... Make sure it's not touching the motor and melted... only reason i ask is I just had to repair 9 melted wires yesterday... it was causing my temp guage to read incorrectly... among other intermittion issues...
 
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