overheating

Joined
Oct 23, 2013
Messages
21
Re: overheating

Chris,

i refer you back to my post #12,

it explains that the word circulating was the clue as you have stated above.

the three diagrams explain the options available to me and again in #12 i had made the descision to use the Barr thermostat housing and plumb it as per your diagram, but your diagram makes it clear how the water will flow through the engine in each option should this question arrise again which it almost certainly will due to the diminished supply of mercruiser parts for this engine and people turning to the aftermarket for alternatives.

here in the states there are many of these pre-alpha drives, especially in the south west, my particular engine/drive/boat originally started life in the U.K., i was inflicted with this boat in 1993, with the engine in poor state and the drive in even poorer shape.

i was moving to the U.S.A. Texas in fact and used it to transport, on a trailer all of my tools from England, i then moved to San Diego California a year later, i did not do anything with it apart from storage.

i returned to england at the end of 93 but left it in storage, it wasn't until 2000 that i re-captured it when i returned to the states in Arizona, but alas, i moved again to Florida, it carried out the same transport duties for that trip and the return to Arizona five years later.

this year is the 40th. aniversary of it's production and the 20th. aniversary of me owning it, so i thought it was time to get stuck in to it.

when i have completed the modifications i will post some pictures of same for reference.

i have still to paint the upper hull and do the interior before i can move on to my next project, since i have been in Arizona, 7 years, i have built a 1700 sq.ft. workshop, then a 1350 sq.ft. house, a sports car of my own design and the boat, all without the help of others, you can view my car on Locostusa.com.

i guess it's summertime in W.A. now, is it good boating weather or like summer here, TOO DARN HOT.

regards, John
 
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achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Re: overheating

Chris,

i refer you back to my post #12,

I just re-read post 12... You pretty much got it right...

john hennessy said:
it explains that the word circulating was the clue as you have stated above.

the three diagrams explain the options available to me and again in #12 i had made the descision to use the Barr thermostat housing and plumb it as per your diagram, but your diagram makes it clear how the water will flow through the engine in each option should this question arrise again which it almost certainly will due to the diminished supply of mercruiser parts for this engine and people turning to the aftermarket for alternatives.

As I said in one of my posts, that engine is now a MINIMUM of 35 years old... I suspect there are not that many of them left out there...

john hennessy said:
here in the states there are many of these pre-alpha drives, especially in the south west, my particular engine/drive/boat originally started life in the U.K., i was inflicted with this boat in 1993, with the engine in poor state and the drive in even poorer shape.

There are the same number of 'pre-alpha' drives in the US as Australia, about 16. (had this discussion too... Click here for an 'educational' read -> http://forums.iboats.com/mercruiser...ve-needs-help-go-down-597987.html#post4160821)

BTW, the drive you have is an MC-1. The decal on it saying '888' is an engine designator, not the drive model....

john hennessy said:
.....i guess it's summertime in W.A. now, is it good boating weather or like summer here, TOO DARN HOT.

regards, John

No such thing as 'too hot' :D It just means longer in the water :D :D (read my signature ;))

Good luck.
 

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Re: overheating

Nice job Chris. It makes sense to me now. That Bar thermostat must have a small bypass to get water to manifold when closed?
Thanks for taking the time to draw all those diagrams up!

Ed,

Just to clear up this thread... The bypass is not 'small', and it's part of the housing casting, not the thermostat itself. It's actually big enough to flow all the water from the raw water pump without too much restriction. The only reason the 'new' water would go straight to the manifolds is if the thermostat is closed. When the thermostat is open the 'new' water is grabbed by the circ pump and pushed into the engine, displacing the current 'hot' water and forcing it passed the (now open) thermostat and out to the manifolds by the same passages the 'new' water would have taken had the thermostat been closed... When the new cooler water hits the thermostat (after travelling around the block and heads), the thermostat closes, and waits for the water to get hot enough to open again, repeating the cycle... Any time the thermostat is closed, 'new' water can not enter the engine (because the engine is already full and the thermostat, being closed, will not allow any of that water out), it MUST go out of the thermostat housing directly to the manifolds. The raw water pump can not 'shut off', it just keeps pumping water in.... :D And that is how we keep the manifolds cool, regardless of whether the thermostat is open or closed... ;)

I hope that makes sense... :noidea:

Chris.......
 
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84EdH

Chief Petty Officer
Joined
Apr 30, 2011
Messages
575
Re: overheating

That is a great description of the system. I have thought forever that once t-stat opened, it stayed open until cool down after shutoff. Like in a car. The difference is that the boat keeps loading in cool water: thus cycling thermostat.

Thanks again Chris !
 
Joined
Oct 23, 2013
Messages
21
Re: overheating

Ed,

in a car, the thermostat does actually close, dependant upon the speed of the vehicle, the effectiveness of the fan, wether the fan drives all the time or is fitted with a viscous clutch, wether the heater is on or off and the ambient temperature amongst other factors.

a good automotive cooling system would not work correctly in warm weather if the thermostat were to always be open in cold weather, it would cause overheating, without the benifit of a heater loosing temperature, hot air from an air conditioning condenser passing through the radiator and ambient temperatures above 100 degrees the thermostat may well be open most of the time but in cold weather when the engine actually struggles to get warm, the thermostat is opening and closing all the time especially in fuel injected computer controlled vehicles where the 02 sensor is trying to maintain a constant mixture, some modern vehicles have an electronically controlled thermostat.

John
 
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Joined
Oct 23, 2013
Messages
21
Re: overheating

new thermostat housing installed,

hoses routed,

connected to hose,

ran the engine, the temp guage almost immediatly went to 150 degrees, then continued to rise, the manifolds were slightly warm to the touch, got out the i.r temp gun, nothing on the engine was over 130 degrees at idle, ran it at 2000 rpm and gauge began to rise to 175 degrees,

the thermostat opened as evident when the top of the thermostat housing became warm, temp gun read 144 degrees both sides of the stat.

i do not believe the gauge is showing the correct engine temp.

i have a Faria gauge and a ford sender unit, do the Faria gauges need a special sender, if so what would be the part number if anyone knows?
 

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Re: overheating

I suggest you start a new thread with the gauge problem.
 

alldodge

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Oct 23, 2013
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Re: overheating

it was just the last thing in my overheating thread as now i can't tell if it is or isn't but i think i have found the number anyway.

as i said, there will be pictures of the final installation when i know how it works, off to the lake now for a test run.
 
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