difference between 160 and 143 thrmostat for alpha I gen II 350 mag freshwater cooled

I have been working on a 1994 350 mag fresh water cooled mercruiser Alpha I Gen II

Used in fresh water only

Boat had a boat load of issues due to bad workmanship and total moranic work.....

The last thing I was chasing was a over heat issue.

1. No gauge reading...............lost thermosts housing ground continuity for sending unit. FIXED

Tested sending unit appeared to be wrong based on a 143 or 160 degree thermostat.........or so I thought.

After changing sending unit temp still climbed over 200*......SH!T

Took thermostat housing off and looked at thermostat...............
Some F'n moron put in a 198* thermostat in this motor.................

The thermostat housing is a one piece, 6 port with OUT the spring ball set up as referenced by the manual.."later models"

Question because it did not have the original thermostat would anyone have any idea which one to replace it with?

A 143 or a 160 and if you could explain why you suggest one over the other.

Thanks

fresh water cooled motors(A/F) usually run the 160 for fuel efficiency

If that is the only reason, the guy who owns the boat (and knows nthing about boats) does not care about fuel economy.
This is 18-19 donzi 4 seater like the sweetheart 16 footer all white with the blue stripe.
Bought it as a go fast boat...

Well I had a old style brass one in my stock...put it in and motor runs on the hose at my house at 160 at 1200 rpms in 90* ambient temps.
I am thinking I will stop tomorrow at the marine store and buy a 140 stainless steel as the manual suggests.

I agree on the 143* for the same reasons stated, I got that info in detail from another forum I visit.

I agree with Gary.
With a Closed Cooling system, the 160° thermostat will maintain higher engine temperature, and for more reasons than simply "fuel efficiency".

The 140° or 143° thermostat is typically used for raw water cooled engines operating in salt water, as to reduce the likelihood of salt crystallization.


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Ok thanks

I just finished installed a new stainless steel 140* and proper gaskets which were not used by whom ever worked on this before.
Boat is ready to go for now....a couple of small issues to be delt with next spring....

This was a can of worms because of absolutely shotty work done by a or a few F'N PIN HEADS.....

Thread title: difference between 160 and 143 thrmostat for alpha I gen II 350 mag freshwater cooled

By freshwater cooled, were you refering to lake/river water with an "open" system.... or to river/lake/ocean water with a "Closed Cooling" system?
My previous response was with regard to a CC System.

If I misunderstood you..... and if this is an open system in river/lake water, you may still want to use the 160° thermostat.


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Non closed cooling...
I meant to type raw water...

I call it closed when it is closed......any other name such as raw or fresh in my eyes is non clo***....

Even merc calls it closed vs raw/freshwater.....