what temp is normal for boat?

[drrm123]

I have a 3.8 v-6 OMC and when I run it on trailer the temp gage never moves? I grounded wire on sending unit and gage pegs hi temp so its working. Water coming from stern is warm to hot -, but not hot enough to burn you though. Should temps get above or around 160 sitting on trailer. Just wondering if I need a temp sending unit or maybe a thermostat?

 

[a70eliminator]

Re: what temp is normal for boat?

My 5.8 tends to run cooler on the muffs, cold water from hose plus no load on the engine I guess, but it will eventaually hit 160. On the lake it comes up to 160 very quickly.

 

[QC]

Re: what temp is normal for boat?

The answer requires a couple of questions . . . Fresh water (Closed) or Raw water (Open) cooling? Thermostat rating?

 

[Haut Medoc]

Re: what temp is normal for boat?

Have you checked the connection at the sender?.....
160 should be OK.....​

 

[drrm123]

Re: what temp is normal for boat?

raw water intake, has an omc v-6 3.8 omc stern drive stringer. I dont know what thermostat is in it if one at all. Maybe I'll pull thermostat housing to see if one is there or if it's stuck open. I backed trailer in water today and ran at about 1500rpm for 15 minutes and the temp gauge never moved. I verified the gauge works but not sure about sending unit.

 

[a70eliminator]

Re: what temp is normal for boat?

Definately replace the T-stat, could be one of those high end stats in there that fail safe, they have a temperture sensitive link that in the case of an overheat will let loose on snap the T-stat open never to close again. They have these for car engines not sure about a boat though, in any event it sounds like you have a bad one or someone has removed it completely.

 

[MikDee]

Re: what temp is normal for boat?

For years the standard Mercruiser, & OMC, marine thermostat was 140 degrees, at times only on the hose, my guage never moved either.

 

[ziggy]

Re: what temp is normal for boat?

thermostats start to open at whatever their designated. a 140 starts to open at 140* and is full open @ +20* or 160......

fwc generally use a 160 t-stat. same thing. starts to open at 160 and is full open @ + 20.........


so yer rwc engine doin 160 or above on the hose would lead me to think somethings up.......might go check yer t-stat. at least see if ya have one. assumin ya have one, boil it in a pan w/ a thermometer and see what it does.....the value of the t-stats that i've had have the number stamped on it for what it is.....mine said 140. but for overheat conditions i understand the first place to look is the seawater impeller. when was the last time ya did yers?

on the hose, my mercruiser 165 reaches just below what is normal operating temp from stone cold.... i'd give ya numbers but my gage don't have numbers, just green and red w/hashmarks.........

 

[drrm123]

Re: what temp is normal for boat?

Looking at the small diagram in Seloc manual I bought I just wanted to make sure I understood that a portion of water remains in engine till it heats up and the other parts still goes out the manifolds to make sure they remain cool. Even though it's not a closed system on my boat.

 

[QC]

Re: what temp is normal for boat?

You are correct ^^^ Maybe a better way to put it is that all of the water that finds it's way into the engine goes out through the manifolds and risers. Some is diverted through the engine when the thermostat is partially or completely open.

 

[drrm123]

Re: what temp is normal for boat?

I found out what it was today when I pulled the thermostat housing....................................There is no thermostat in it so I'll order one of those also.................trying a place one large order to save on taxes and shipping. Thank you everyone for the input.

 

[gdombroski]

Re: what temp is normal for boat?

Are you sure there is no thermostat? I thought the same thing when I removed the housing on my 5.8l and didn't see one in the block like on a car. It was mounted in the inside toip of the housing.

 

[THE BEEF]

Re: what temp is normal for boat?

I run a 305 200hp 800 stringer. Temp all last summer 160 degrees.
NO problems
Beef

 

[THE BEEF]

Re: what temp is normal for boat?

I thought that too,no thermostat. ITs not like a car its up inside the housing
held in by a rubber type o ring.
Beef

 

[drrm123]

Re: what temp is normal for boat?

I'll check again, but sure i felt the inside of the thermostat housing.

 

[THE BEEF]

Re: what temp is normal for boat?

Look uo inside I made the same mistake.Its smaller the a car thermostat.
I couldn't find it either at first. My marine dealer told me where to look.
Good luck
Beef

 

[drrm123]

Re: what temp is normal for boat?

Looked again today and definitely no thermostat. So I'll add that to my order. Smelled like engine was running rich so by it not getting up to proper temperture I'll see if it burns cleaner when I get thermo put in.

 

[Lou C]

Re: what temp is normal for boat?

Looked again today and definitely no thermostat.

I have never seen a 3.8 thermo housing, but on the 4.3 V-6 and the 5.0/5.7s there is a rubber ring that holds the thermo into the housing, it fits in a groove in the thermo housing. Look over on the doug russell site, they have diagrams so you can tell what you need to get it back together.

My 88 4.3 with a 160* stat runs pretty much at 160 all the time once it's warmed up, the way I can tell it's time to replace the stat is when it takes too long to warm up, or only warms up to 160 when running at speed and cools off to 120 at low speeds. They seem to last about 2 seasons in salt water before they get sticky and make the engine run cool.

 

[Scaaty]

Re: what temp is normal for boat?

Raw water cooled, do a 140 stat...Fresh, ya didn't mention...helps..

 

[drrm123]

Re: what temp is normal for boat?

I got a thermostat today and installed it, will see how it runs in about a week. Thanks for the info again.