Normal running temp?

[navicache]

Was wondering what the normal running temp should be for a merc 5.7 ltr motor with an alpha one outdrive on it?<br /><br />We just changed the impellar pump and hooked it to a set of muffs, I run around 180 degree's at idle on the muffs. Will this drop in the lake or can I expect same temp? also what is an ideal range?<br /><br />Thanks in advance.

 

[mike456]

Re: Normal running temp?

depends what t-stat is in it. If its raw water cooled (like mine) then you need 140 degree. With that temp should stay near 140 at idle. If its fresh water (closed system) then you need 160 degree. With that you should stay near 160. 180 sounds a bit high at idle. Check to see if there is a t-stat. maybe someone removed it. Not a good idea to run without it.

 

[ross_larter]

Re: Normal running temp?

my raw water cooled never seems to go above 130, is that bad?

 

[sumcat1]

Re: Normal running temp?

My 4.3 is raw water cooled and the spec sheet says it should have a 160 deg thermostat. It runs just above 180 at idle or cruise.New boat,30hrs.Maybe temp gages are not any better than speedos.

 

[Haut Medoc]

Re: Normal running temp?

You don't say what year or if you are FWC or RWCooled......<br />Either way 180 is warm, but not overheating......<br />Ross Larter, it depends on what engine you have, but 130 should be ok .......JK

 

[Boomyal]

Re: Normal running temp?

Originally posted by Haut Medoc:<br /> Either way 180 is warm, but not overheating......

Heck Haut, I thought this might be one arena that we could agree in. <br /><br />If the gent has closed cooling, 180 deg would be ideal. If so, a 180 deg stat should effectively keep it at 180, idle thru wot.

 

[navicache]

Re: Normal running temp?

The boat is a 1996 Imperial 21' cuddy with a 5.7 ltr mercruiser SN# 0f756305 using a alpha one outdrive.<br />It has been used before I bought it a few times in salt water, so I really don't know what it has for cooling (newb here)<br /><br />We changed the impellar for a new one and also added high perf lower end oil.<br /><br />We fired it up on muffs in the driveway and she climbed to 180 and leveled off. Just wondering if she is not getting enough water to keep her cool or if she will run cooler in the lake once she has all she can handle.

 

[Don S]

Re: Normal running temp?

A closed cooling system has a heat exchanger mounted on the engine (usually in the front) and uses antifreeze to cool the engine, and sometimes the manifolds. But not the risers.<br />A raw water cooled engine has no heat exchanger and has no heat exchanger.<br />With a closed system, they usually run a 160° thermostat.<br />Running on the hose could also be a problem. If you have low pressure, or very long hose, it will cause them to run hotter also. Best thing to do would be to put it in the water and see how it acts (A test run) to get the feel for your new boat. Get one of those laser temp guns and make sure what the temps are at different places on the engine.

 

[GabeNalley]

Re: Normal running temp?

If it is leveling off then it will be t-stat. If it drops on high speed then you need a new impellor or circulating pump. Sounds like you have replaced the impellor so look into that. Just think 180 is better on fuel then 140 so FLOOR THAT BAD BOY!

 

[navicache]

Re: Normal running temp?

I am located in Upstate , ny. I bought the boat at an auction and believe it was run in salt water on long island for a period due to the sticker on the trailer.<br /><br />I have not even had the fun of placing it in lake ontario as of yet, been too busy cleaning her up and changing the outdrive oil and impellar kit.<br />I ran it on muffs afterwards and noticed that the water is only pumping out of the stern side behind the outdrive. Is it supposed to be pumping out of both sides behind the outdrive? or doesnt it matter. (remember, this is all on muffs) I am by no means a boat mechanic and much of this I am learning from you guys with a gratitude I can not express enough. I just want to make sure i am safe to run the lake with what i have.<br />Thanks for any other info. Egine serial # is 0f756305 , transom serial # is 0f647364 drive is 0f693378

 

[sker crunch]

Re: Normal running temp?

I'm far from an expert but mine pumps out both sides of the outdrive and the prop.

 

[Don S]

Re: Normal running temp?

Do you have raw water cooling or a closed cooling system? Serial number won't give that info.

 

[navicache]

Re: Normal running temp?

I believe its raw water cooling.