water temp only 110 degrees

[sebagolake19]

Hi Guys,

Great forum. I took my boat (1987 fourwinns 190 horizon w/ merc 470 165hp) out last saturday for a cruise on the lake. The motor ran great but it never warmed up past about 110 degrees. The lake water was 43 degrees. It it normal for the motor to run that cold when the lake water is that cold?

 

[Don S]

Re: water temp only 110 degrees

Replace the thermostat.

 

[sebagolake19]

Re: water temp only 110 degrees

Replace the thermostat.

On the 3.7 do I remove the anti-freeze drain plug on the heat exchanger to drain the anit-freeze? Unbolt the two bolts and remove the thermostat. Replace the drain plug and fill the exhaust elbow with anti-freeze 50/50 mix? I assume I need to remove the drain plug on the back of the boat so the anti-freeze can drain out of the boat. Wash out with water?

 

[Bondo]

Re: water temp only 110 degrees

Ayuh,.....

That sounds like a reasonable plan.....

 

[sebagolake19]

Re: water temp only 110 degrees

Thanks for the replies. I replaced my thermostat today. One thing I noticed is that the hose below the thermostat housing warms up when the motor is warming up. I would have thought that hose would have stayed cool until the thermostat opened up. Anyway, I ran the boat on the bunny ear flushers for about 10 minutes tonight and it got to about 120 degrees. That is higher than when I took the boat out last weekend and ran it for about 45 minutes. I have the 4" cooler and I'm suprised how well it can cool. I'm going to take it out tomorrow in a lake that the water is about 45 degrees. How long should it take to get to the targeted 160 degrees?

 

[Bondo]

Re: water temp only 110 degrees

and ran it for about 45 minutes.

Ayuh,......... That otta do it.......

 

[sebagolake19]

Re: water temp only 110 degrees

Ayuh,......... That otta do it.......

Hi Bondo,

It looks like you are the guy to go to on this forum.

I'm not sure what your last post mean?

After 45 minutes it should be up to 160 degrees?

 

[Lakester]

Re: water temp only 110 degrees

Hi Bondo,

It looks like you are the guy to go to on this forum.

I'm not sure what your last post mean?

After 45 minutes it should be up to 160 degrees?

hello,

naw, he just made loads of posts. heck, u read these threads and u will be an expert soon, too....

yes, that is what he meant.

regards and "velcome aboard!!"

lakester

 

[Bondo]

Re: water temp only 110 degrees

Hi Bondo,

It looks like you are the guy to go to on this forum.

naw, he just made loads of posts. heck, u read these threads and u will be an expert soon, too....

Ayuh,....... That IS what I meant,......

And,.... Nope,....
Don, or RP, or Rodbolt, or 1 of the Other many Marine Techs are the Go To Guys......

I'm just an ole Mechanic,..... With a Doctorate degree in Common Sense.......

 

[sebagolake19]

Re: water temp only 110 degrees

Well it's raining here so we did not go out on the boat. I did run the boat on the flusher ears for about 30 minutes. It still did not go over 130 degrees acording to the gauge. I'm thinking my gauge is incorrect. With a new thermostat there is no reason why the boat would run cold. Am I right?

 

[sebagolake19]

Re: water temp only 110 degrees

I put in a Sierra 18-3555 thermostat. I placed it so the pointy side was facing down and the side with all the springs was facing up. That is hoe the old one came out. Can someone please confirm if that is correct.


What's the chances of installing a new faulty thermostat? Can someone explain why the hose below the thermostat warms up when the motor warms up? When I was installing the new thermostat I noticed on the gasket there were four holes. Two of the holes aliegned with two ports that seems to be a bypass of some sort. Just wondering how to diagnois this situation? I'm unsure if it is reaching the correct temp. or not? It might be my temp guage is not working correctly? Is this something I should worry about or not?

 

[Dakota47]

Re: water temp only 110 degrees

put it on the lake and then let us know how hot it gets..

 

[sebagolake19]

Re: water temp only 110 degrees

Does anyone have any suggestions here? Can a temp sensor go bad? I believe that if the thermostat was working the hose below it should remain cold until the motor reaches operating temperature. It just seems hard to believe that a new thermostat would act like the one I just replaced.

 

[Bondo]

Re: water temp only 110 degrees

Ayuh,.....

Until you Spash the boat,+ Try it,..... You might be chasing a Ghost....

I believe that if the thermostat was working the hose below it should remain cold until the motor reaches operating temperature.

The Big Hose below the T-Stat housing is moving the water under the T-Stat, thru the block....That's why that Waterpump is called the Recirculating pump,.. It recirculates the water thru the block,+ the Big Hose, til the T-Stat Opens....

It'll get Colder went the T-Stat opens....

 

[sebagolake19]

Re: water temp only 110 degrees

Ayuh,.....

Until you Spash the boat,+ Try it,..... You might be chasing a Ghost....



The Big Hose below the T-Stat housing is moving the water under the T-Stat, thru the block....That's why that Waterpump is called the Recirculating pump,.. It recirculates the water thru the block,+ the Big Hose, til the T-Stat Opens....

It'll get Colder went the T-Stat opens....

Bondo,

I appreciate your reply. Next weekend will be the first time I can actually put the boat in the water and try it.

As far as the big hose BELOW the thermostat goes, it runs directly from the T-Stat housing to the heat exchanger. It does not recirculate thru the block. That is why I'm stumped. According to the mercruiser manual that came with the boat, the flow direction runs from the exhaust manifold / elbow down through the Thermostat and into the heat exchanger. That is why it seems there is no t-stat in the boat. The hose gets warm when the engine is warming up and the boat never gets close to the 160 degree point. Actually after running for 30 minutes on the muffs I can still put my hand on the exhaust manifold / elbow.

I hose goes from the t-stat housing down to the heat exchanger and back to the exhaust manifold from a hose on the front of the heat exchanger. That hose on the front of the heat exchanger remains cool. I could ubderstand if that hose were hot it would be warming up in the reverse direction but it isn't.

I'm stumped!!!!

 

[Bondo]

Re: water temp only 110 degrees

Ayuh,...... I Forgot we're puttering with a 470,....

That hose on the front of the heat exchanger remains cool.

That's because it's the Cold freshwater return......

Actually after running for 30 minutes on the muffs I can still put my hand on the exhaust manifold / elbow.

Ayuh,..... Again,... Running on the muffs, with No Load,... Means nearly Nothing....

I'm trying to capture a drawing from my 470 Factory Manual,+ having No Luck with it,.... It's pretty much locked up my 'puter.....
I'll try to post this, reboot,+ come back.....

 

[sebagolake19]

Re: water temp only 110 degrees

Ayuh,...... I Forgot we're puttering with a 470,....


That's because it's the Cold freshwater return......



Ayuh,..... Again,... Running on the muffs, with No Load,... Means nearly Nothing....

I'm trying to capture a drawing from my 470 Factory Manual,+ having No Luck with it,.... It's pretty much locked up my 'puter.....
I'll try to post this, reboot,+ come back.....

Thanks for the post Bondo.

I have a diagram of the water flow in the manual that came with the boat. I unfortunately do not have a scanner. It does show that the hose on the from of the motor coming out of the heat exchanger is the cooled anti-freeze after it goes through the exchanger.

 

[Coors]

Re: water temp only 110 degrees

An infrared temp gun might tell the truth?

 

[renny1]

Re: water temp only 110 degrees

just a quick suggestion
if you still have your old thermostat stick it in some hot water and see if it opens up if it does then you know it isnt your thermostat but you put a new one in anyway imho that is the first thing to try

 

[sebagolake19]

Re: water temp only 110 degrees

Hi Guys,

Thanks for the help. I contacted the original owner of the boat. The guy I purchased it from He said he noticed that the temp gauge was reading low so he had a mechanic check it out. The mmechanic confirmed that it is running at the normal engine tempurature. He said it must be either the sender, gauge or the wire. How do I check to see if the sender, gauges are working? I know the wire is working at least a little bit because if I remove the wires from the back of the gauge the gauge dies. The boat looks brand new and the gauges show no sign of corrosion or wear. I'm going to try grounding the sender and seeing if that pins my gauge. I believe that is the only way to kind of test either one.

Thanks for your help.