Mercruiser 3.7 Thermostat Question

[Old Yeller Boater]

I ordered a sierra 18-3667 replacement thermostat for my 3.7 merc. This is a dumb question, but I just want to be double sure. Which way does the spring side go? Toward the exhaust manifold, or toward the hose? thanks!

 

[flyrodman]

Re: Mercruiser 3.7 Thermostat Question

Spring goes towards manifold

 

[Old Yeller Boater]

Re: Mercruiser 3.7 Thermostat Question

whew....thanks!

 

[ktbarrentine]

Re: Mercruiser 3.7 Thermostat Question

Is this what we're talkin' about...cause that didnt sound right... just checkin.
http://www.crowleymarine.com/mercury-outboard/parts/908_100.cfm

 

[Eric 3.7LX Alpha 1]

Re: Mercruiser 3.7 Thermostat Question

That pic in the link above has the tstat the wrong way according to manual 8 pg. 6A-8 & 9. I will attach them in a few

 

[Old Yeller Boater]

Re: Mercruiser 3.7 Thermostat Question

Yes, that's what I was asking about. After installing it last night (based on how the old one came out), I got to looking at the diagram in your link, and had me concerned It was backwards. If it WAS backwards, that would explain why I'm overheating, however, I've already found and replaced a bad impeller which I believe to be the culprit.

 

[Don S]

Re: Mercruiser 3.7 Thermostat Question

What is the serial number of your engine? 3.7 just doesn't tell the whole story.

 

[Old Yeller Boater]

Re: Mercruiser 3.7 Thermostat Question

Unfortunately, that's not an easy question. This boat had the motor replaced in 2005 (it's an 87 Larson DC190). it was replaced with a crate motor. Picture is attached, but as best I can tell, the SN is 93300184.

 

[Don S]

Re: Mercruiser 3.7 Thermostat Question

This should cover your engine. If the engine was an 87, then it's a model 165.



NOTE: The picture of the thermostat in the above picture is upside down. DO NOT install it that way.
Use the pictures below, and pay attention to the "Umbrella"

 

[Old Yeller Boater]

Re: Mercruiser 3.7 Thermostat Question

Don, is there someplace else on the block that I could look for a serial number? That would certainly make it easier to look things up.

But thank you so much for the info above. I've been floundering trying to verify the right original motor and have been looking at diagrams to determine which was NOT mine.

 

[ktbarrentine]

Re: Mercruiser 3.7 Thermostat Question

Great info! Wonder how many poor souls have installed theirs upside down because of that diagram.... Forum proves it worth once again!

 

[Don S]

Re: Mercruiser 3.7 Thermostat Question

Don, is there someplace else on the block that I could look for a serial number? That would certainly make it easier to look things up.

But thank you so much for the info above. I've been floundering trying to verify the right original motor and have been looking at diagrams to determine which was NOT mine.

Post the drives serial number and I'll see if I can match SN with year. If no one has changed the drive.

 

[Old Yeller Boater]

Re: Mercruiser 3.7 Thermostat Question

Post the drives serial number and I'll see if I can match SN with year. If no one has changed the drive.

I don't have it with me, but will get it. I'm almost 100% sure the outdrive is original. I'm only the third owner of the boat and the previous owner new the first. Thanks!