overheating 302

[northvanwatertaxi]

Just pulled the motor to change the bell housing changed the water pump because it's been about 4 years and the engine was getting hot at cruising speed,
my aligned alighned the shaft and gave me the green light , the engine got new marine plug wires and is starting and running much better, except, its getting hot at idle (it's on muffs) i changed the engine thermostat, but it's still hot,
took the heat exchanger off cleaned it and found that the water above the pump is clean near the pump it's dirty.... think it's the water pump but not sure how to check that. obviously it's not circulating
is it a marine only part? it could be blocked by dirt so should i take the pump off?

 

[northvanwatertaxi]

Re: overheating 302

"my friend helped me align the motor"
Its a mercruiser pre alpha "R" and the engine is ford 888

 

[northvanwatertaxi]

Re: overheating 302

fwc, fresh water cooled

 

[northvanwatertaxi]

Re: overheating 302

I was reading my post the sterndrive pump is new
the fresh water pump near the engine is the one i'm reffering to. I changed the engine thermostat, found another one in the heat exchanger and just tested it it's ok

 

[calwldlif]

Re: overheating 302

I am confused.
Fresh water cooled.(Closed system)?
Are you asking about Raw water pump
(picks up external water)?

 

[northvanwatertaxi]

Re: overheating 302

sorry about that
closed circulating ciculating pump on the engine is the I'm reffering' reffering to the raw water system ok ok

 

[northvanwatertaxi]

Re: overheating 302

this spell check doubles up the words
Maybe it's the heater i'm going to bypass it after i get the water pump and the heat exchanger back on I think the problem is a plugged heater because when I pulled the heater hose off the engine anti freeze poured out of the 2 circulating pump holes that the pump normaly covers
the good news is the heat exchanger is clean.

 

[Haut Medoc]

Re: overheating 302


I doubt that your problem is the engine's circulating......
It would leak before it would quit ....
& it would still work after it leaked, unless the vanes were rottted off, & I dobt that with a closed system...
How do you know the closed side of the exchanger is clean?
You can't see the internals on that side of the exchanger.....
I suspect the closed side of your heat exchanger is partially clogged...
First, I would verify that i am getting sufficient water flow after the impeller change....
Second, when was the last the exhaust risers were off & inspected.....
Third, I would take the exchanger to a radiator shop & have it boiled out.....
I think your problem is restriction.....
& it definitely is not related to your heater......JK

 

[Haut Medoc]

Re: overheating 302

Add the word "pump" to the end of the first sentence.....

 

[NoName]

Re: overheating 302

I have the same engine with the same problem. See my post "Blown Head Gasket ?". The most likely cause of over-heating is the impeller in the lower unit. To test it, start the engine with the earmuffs on and pull the hose that feeds water from the lower unit to the thermostat housing. If the impeller is good, water should gush from the hose. Little or no water means a bad impeller. If you have lots of water, you have other problems.

 

[northvanwatertaxi]

Re: overheating 302

opened up the ends of the heat exchanger where the raw water passes and found lots of the holes plugged so i ran of water through the opposite end and gave it a flush. then tested the closed side and its fine.
tested the riser to exaust dumps, they were fire so i checked out the maifolds by hooking a gadren hose held with a hose clamp , and they were fine too
my circulating pump was fine, I should have left it alone because when i took it out, a bolt snapped in half , I drilled and taped out the broken bolt and now i'm looking for a new pump
I'm sure they are not cheap.

 

[northvanwatertaxi]

Re: overheating 302

sorry about the spelling text is way too small, My manifolds are not on fire

 

[Haut Medoc]

Re: overheating 302

Don't be so sure of the closed side of the heat exchanger.....
Unless you have x-ray vision, you can't possibly see the closed side of the exchanger....
The innards, can & do become clogged, especially when the water used to mix with the anti-freeze is high in mineral content....
This reduces the efficientcy of the raw water side because it doesn't exchange like it is supposed to......
One thing that is unusual is that you have two thermostats?....
I only have one....
It is between the exchanger & block.....
I run a 142*, with a 160* it will get hotter than I like @ idle....
Are your manifolds not part of the closed system?
Mine are....
If they are part of the closed system, they are not the problem.....& I'm glad they are not on fire!8)
You are either not getting enough water in, enough water out or there is not enough of the exchanger surface, exchanging heat....
The reason I keep coming back to the exchanger is that I had your same symptoms, & after I had gone throuhg every part I came back to the exchanger, got a used one at a local shop & my problem was gone....
For lesst han a hundred bucks it can be boiled out at a radiator shop...
I have the same set-up & that is what worked for me,FWIW
That is one of the reasons to use distilled water, just like in a battery.....
Do the test that no-name suggests & verify that you have good flow from the hose that comes from the transom to the raw water side of the heat exchanger.....

 

[northvanwatertaxi]

Re: overheating 302

two thermostats?....
I only have one.... one thermostat is on the heat exhanger the other is on the block above the water circulating pump


I run a 142*, with a 160* it will get hotter than I like @ idle....how hot does it get?

i ran a garden hose though closed side the exchanger tank and it just pours out unrestricted
But if I take it out and it overheats again I have a spare exchanger

 

[Haut Medoc]

Re: overheating 302

By all means try the spare exchanger & see if that does the trick.....
Just because it pours out doesn't mean a thing......
If the spaces between the sea water tubes get closed up, you have lost alot of your heat exchange surface.....
Mine did the same thing & that was what fooled me....
If you have a spare throw it on, it a'int hard at all....
Esp if you have had the circulating pump off.....
Where are you located BTW?
As far as hot, it will get up to the 'redline'....
My gauge does not have degree increments, only yellow, green & red....
With the 142* it stays comfortably in the green at all times....
I gotta get me one of those point & read thermos!

 

[northvanwatertaxi]

Re: overheating 302

If anyone knows why the ford 302 just keeps overheating, please speak up even if it's to say get a chevy,
on the hose it was running fine, so today in the water I let it idle and the temp went up after letting it run awhile, so I didnt dare take it out.
I took the heat exchanger out and installed another spare at the dock and the temp is still up.. same thing.
the Last pump mysteriously melted down after driving slow temp just creeps up so this is a new impeller and housing. When I tested the hose before the heat exchanger there was good flow
at the risers I took the hose off and got lots of flow only after I removed the hose it had been running for awhile getting hot is this normal, isnt the pump self primeing ?
after changing the heat exchanger that happend. and is there any way I might have air lock in the fresh water system? maybe I dont burp it right?
How much flow should I get from the 5|8" heater hose at idle? ( it comes out of the middle of the manifold retuns into the old heat exchanger now it's plugged)
The risers have been changed I used my spares.
Thermostat opens but it had to go to 180 before it opened.
Nothing seens to work, I have been thinking of a chev 350 for a fresh start.
I love my boat not real sure about the engine.

 

[calwldlif]

Re: overheating 302

If on the hose it is ok
then why in the water is it not?
On the hose I guess you have pressure, right?

Do you have a bucket, tote, trashcan big
enough to put drive and pickup in?
There are 20-40 gallon storage "bins"
(I grow veggies in them) that might work.

Put drive in container, fill. Keep hose filling
the container while you run motor.
This will tell you if you have suction problems.

I know old 302's blocks are known to have slag
crud when rusty. Backflush if the motor "sucks"
water ok.

 

[northvanwatertaxi]

Re: overheating 302

Thanks for the idea, cal. mechanic friend has wire muffs that close up when the pump "sucks" at first the new impeller didnt pump so he told me to shut down then he primed the heat exchanger and it started pumping. that's strange because it seems like it is weak but pumps alot of water and I made sure I back flushed it all out after the old pump blew apart.
I read the 305 at idle and will check my temp sensor but he doesnt have a heat gun....all the work i did and the holiday I was planning is toast , new starter is notworking then a tire blew on the trailer no hurry getting back to me i'm not going anywhere.

 

[northvanwatertaxi]

Re: overheating 302

when you say back flush to remove deposits, that can only be good! I have already flushed the pipes by taking them off and funning a hose though them is that what you meant cal?
Is there a way to tell if the head gasket are no good?

 

[POINTER94]

Re: overheating 302

check this thread, it is rather comprehensive thanks to blk n blu.

http://www.iboats.com/bbboard/bbBoard.cgi?a=viewthread;fid=24;gtid=1126504