Can some one help? prob. stupid question

WAVENBYE2 · May 31, 2007

OK, I know this is prob. going to sound stupid but if you look on the section in (cooling system) It isn't the same setup as on the picture I am showing you(the exact picture to what I have in boat) Question:You see the four hoses on the front connecting to the center? I have that same exact thing, when I run the engine I can definitely feel water flowing in the two smaller hoses (TOP), I don't feel any water flowing in the two bigger hoses(BOTTOM) or any pressure built up either. the illustration they use shows a different set up than mine, they show coolant being used with fresh water too??? Isn't mine 100% fresh water cooling system?? The picture is identical to what my set-up is. Please clearify this for me !! THANKS...PAT

88wellcraft · May 31, 2007

Re: Can some one help? prob. stupid question

I t doesn't look fresh water cooled to me. I f it is fresh water cooled it will have a heat exchanger that acts sort of like a radiator. The heat exchanger will have a cap on it like a radiator and you fill it up with water/antifreeze like you would a car.

Don S · May 31, 2007

Re: Can some one help? prob. stupid question

Sooooooo, you have basically a Mercruiser of some unknown year and model with 6 hoses going to the thermostat housing correct?
You also aren't going to feel any water flowing, or pressure build up in a raw water cooled engine.
You have a RAW or SEA water cooling system. Doesn't matter if you boat in a fresh water lake, it's called Raw or Sea water cooled.
Freshwater cooling is with a heat exchanger and uses RAW/SEA water to cool the coolant (aka as freshwater).

Does my gibberish make any sense to you??????

WAVENBYE2 · May 31, 2007

Re: Can some one help? prob. stupid question

Yes , it does make sense you just confirmed what I what I thought. and there is no radiator cap on it any where, water comes out the prop and bottom of stern drive , There is absolutely no where to put coolant like the manual shows, I do feel water flowing through the top two 1" inch hoses but not the bottom two hoses which are bigger, just be patient Don , I am doing every thing I can to learn as much as I can,some times I think my brain is working so much to try to learn every thing I might confuse my self sometimes

so far I think I'm doing pretty darn good working on everything my self , the winterization worked with out a hitch

did my own tune up too,so far no horror stories like some I have read (Done by paid pros.) I think I'm doing good so far,with all of your help of course

Thanks..PAT

Hermyboy3000 · May 31, 2007

I had a similar issue with mine.

I had a similar issue with mine.

I know you've got a Merc, I've got a Volvo but this might be the same issue.
I had a thermostat that was stuck in the open position and was keeping water from flowing properly. I was getting a ton of steam in my exhaust (don't think this is normal). I replaced the thermo and the problem was solved. No more steam and no more overheating! Maybe you have the same problem. Not sure, just MHO.

WAVENBYE2 · May 31, 2007

Re: Can some one help? prob. stupid question

Right behind where you turned it red the thermostat is right behind it, And its working pretty good, Every time I run her I keep an eye on the temp. gauge, gets about 195-200F* then kicks it down to 150F* and holding. Thermostat housing has two 1" hoses .one for in, the other out. Thanks Guys...OH its a 91 bayliner with a 97 block, every thing else is original 91 parts

88wellcraft · Jun 1, 2007

Re: Can some one help? prob. stupid question

Unless I missed something.....he didn't state if he was having a problem.....just clarification as to which setup he has. If your thermostat is stuck in the open position the gauge should show the temp too low. As far as the steam....I couldn't tell ya. As far as the the gauge showing 195-200...thats too high. are you sure you have the right one....marine applications of thermostats generally open in the 160-170 range and should hold there. Auto applications are usually in the 180-190 range.

Don S · Jun 1, 2007

Re: Can some one help? prob. stupid question

Here is a drawing out of the Merc Service manual that should help you understand how your cooling system works.
And if your temp is going to 195-200, then you have a problem rather you know it or not. A marine gas engine should never get that hot. It's not that it will hurt the engine, it's the other problems in an enclosed space.

Maclin · Jun 1, 2007

Re: Can some one help? prob. stupid question

One thing to keep in mind is that water temperature sending units are desiged to work while surrounded by fluid. They may or may not register steam as hot. If your thermostat is stuck closed and the engine boils the cooling water the temp gauge could actually show a drop in temperature as the coolant water turns to steam.

If the 195-200 degrees shown on your temp gauge is accurate and the thermostat is operating properly then it should level out as it approaches 180-190 with no spike.

If you are boiling the coolant then the temp gauge will rise past the high mark, then start dropping after a few minutes as the coolant turns to steam.

On my older (1991) Volvo 5.7 the thermostat is installed up in the top of the housing, no acccess from the top/outside of the housing. This may not apply to yours. There is a grommet and clip that hold it up in the well at the top of the housing. If it is not installed properly it will affect the operation of even a brand new thermostat.

WAVENBYE2 · Jun 1, 2007

Re: Can some one help? prob. stupid question

Thanks again DON S , Yes that is the exact one , The manual that you sent me last week was showing different cooling systems , again thats when my eye brow raises, I didn't think it was supposed to have coolant, I down loaded it to my boat manuals THANK Again !! And yes the temp. raises to about 180-190F* before thermostat kicks in and lowers the temp to about 160F*, so you think it might be automotive thermostat? if so there is a place about 35 ml. from here where I can buy a marine thermostat. OH by the way after doing some research I found out the block is a 97, everything else is original 91.Thanks for all your help again, I would be f***ed with out all your help.

Maclin · Jun 1, 2007

Re: Can some one help? prob. stupid question

Thermostat operation does not differ between automotive or marine application. There is only an operating temperature range rating. A properly operating thermostat in a properly operating cooling system will keep the temperature even. There will not be a spike that high then come back down. The temp should start rising towards 180 or so then stay there, not noticeably go past then come back down. Shouldn't vary more than 3-4 needle widths as you run it thru the paces.

WAVENBYE2 · Jun 1, 2007

Re: Can some one help? prob. stupid question

OK then let me ask you this, could the drop in temperture be due to I am running the boat on muffs and the longer I let it run the colder the water from below ground gets ??? So in the lake it should stay at one temp. due to the water being one temp??

88wellcraft · Jun 1, 2007

Re: Can some one help? prob. stupid question

When I run mine on muffs the temp stays low but on the water it is fine. I've always thought that the pressure of the hose keeps it cooler as the pump in the outdrive does not pull in as much water on the water as the hose gives on muffs.

does that wording make any sense?

WAVENBYE2 · Jun 1, 2007

Re: Can some one help? prob. stupid question

Yes, it makes a lot of sense, I also figured water temp. had somthing to do wit it too.

Don S · Jun 1, 2007

Re: Can some one help? prob. stupid question

Those raw water pumps will put out more volume in the water than on muffs. On muffs, there are too many places for air to get it. It's still plenty to cool the engine while at idle on muffs NOT under a load.
When in the water and moving there is a load on the engine that causes it to get warmer.
Also, the way that thermostat housing is designed, when the engine starts and the raw water pump is pumping water, there is water on both sides of the thermostat. Air is purged almost immediatly.

WAVENBYE2 · Jun 1, 2007

Re: Can some one help? prob. stupid question

YA BUDDY, I am getting ready to put the port side exhaust man. back on and fire my baby back up..I don't ever run above 650 rpms.she is about ready Thanks to you all. and specail thanks to you Don S for all your identifying manuals too, I down load every one of them..

THANKS ALL >>>PAT

Can some one help? prob. stupid question

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