I have a Sea Ray with an 888 302 Merc Setup. My engine runs great, but
overheats after 5-10 mins under a load. I pulled the thermostat and it
was stuck 1/2 way open. Just to be safe I replaced. Once on the water
again, I had the same results, so I pulled the thermostat out just to
rule that out, and I had no change. I am confident that the pump in
the out drive is functioning because my manifolds are filling with
water, and when I removed the thermostat housing water ran out from all
of the hoses. It does not seem that all of the hoses are filling with
water, specifically the lower return hoses. When I had the housing
removed I checked for obstructions, and cleaned the entire unit that
attaches to the block in a solvent tank and then my high temp parts
washer. In my experience it is rare for a circulating pump to fail
without seizing, making noise, or leaking. I wonder if I may have spun
the impeller shaft on that pump. Does anyone have any similar
experiences, or suggestions? Like I said, I know that water is being
drawn up, but not cooling. Thanks in advance for any help!



Ryan

Those log style manifolds and the risers in the 70s early 80s
Mercruisers tend to plug up. You might buy a little time by acid
boiling them. But in my opinion it's better to replace them or upgrade
to a center rise exhaust system. The other part that is prone to
failure is the stern drive water pump. They should be replaced at least
every 2 years.
Jim

Is there a way to test the stern drive pump before I pull my lower
unit. The part that gets me is that I am pulling water up into the
engine. Perhaps it is just not enough. I pulled the circulating pump
and it is functional. When I pulled it a fair amount of water came
pouring out of the system, so I find it difficult to conclude that the
stern pump is not functional.

I had a friend with the exact same symptoms on his inboard (I know,
different animal). We concluded that it couldn't be the impeller since the
boat was in for service recently, and it was replaced. We did the same stuff
(thermostat, etc) and still had the same problem. Something made me ask him
if he had the old parts from the service, and he did. I opened the box that
held the old impeller, and all I saw was a rubber shaft. The fins were
completely destroyed. Now I'm guessing that the bozos at the shop didn't
bother to flush the motor before they put in the new impeller. I mean, all
those pieces had to go somewhere!

So...I removed the new impeller, and two of the four ports in the housing
were completely clogged with pieces of the old impeller!. I cleaned them
out, reassembled, and the boat has been fine since. I guess what I'm saying
here, is that you can't rule anything out if all else seems to check out OK.

Good luck.

--Mike

"Weldo60" wrote in message
oups.com...
I have a Sea Ray with an 888 302 Merc Setup. My engine runs great, but
overheats after 5-10 mins under a load. I pulled the thermostat and it
was stuck 1/2 way open. Just to be safe I replaced. Once on the water
again, I had the same results, so I pulled the thermostat out just to
rule that out, and I had no change. I am confident that the pump in
the out drive is functioning because my manifolds are filling with
water, and when I removed the thermostat housing water ran out from all
of the hoses. It does not seem that all of the hoses are filling with
water, specifically the lower return hoses. When I had the housing
removed I checked for obstructions, and cleaned the entire unit that
attaches to the block in a solvent tank and then my high temp parts
washer. In my experience it is rare for a circulating pump to fail
without seizing, making noise, or leaking. I wonder if I may have spun
the impeller shaft on that pump. Does anyone have any similar
experiences, or suggestions? Like I said, I know that water is being
drawn up, but not cooling. Thanks in advance for any help!



Ryan

I have thought of that. My Dad had the exact same problem with his
Mariah. What causes me to doubt that scenario is the fact that I am
getting water into the engine. I popped one of the plugs off of the
port manifold and ran the engine while in the water, and water shot out
of the plug for five minutes after the engine was shut down. I just
hate to drop my stern drive if that is not the problem; however, I am
running out of other options. Which brings me to my next question.
How hard is it to drop the stern drive and replace the impeller if it
comes down to that?

It's only 8 nuts holding on the sterndrive. About 2 hours to do the
work. Buy an upper water pump body kit, Stern drive mounting set,
synthetic gear lube, mutual seal, bellow adhesive, grease for the
u-joints, and 8 new stainless nylock nuts. If the bellows look tired
replace them. If you are having a problem with the shift you might as
well fix it while the drive is off. If you can borrow an engine
allignment tool, do so. Do yourself a favor and buy a genuine
Mercruiser service manual.
Jim

if it's more than 2 years old then replace the impeller!

"Weldo60" wrote in message
ups.com...
Is there a way to test the stern drive pump before I pull my lower
unit. The part that gets me is that I am pulling water up into the
engine. Perhaps it is just not enough. I pulled the circulating pump
and it is functional. When I pulled it a fair amount of water came
pouring out of the system, so I find it difficult to conclude that the
stern pump is not functional.

But is it pumping enough volume???


"Weldo60" wrote in message
ups.com...
I have thought of that. My Dad had the exact same problem with his
Mariah. What causes me to doubt that scenario is the fact that I am
getting water into the engine. I popped one of the plugs off of the
port manifold and ran the engine while in the water, and water shot out
of the plug for five minutes after the engine was shut down. I just
hate to drop my stern drive if that is not the problem; however, I am
running out of other options. Which brings me to my next question.
How hard is it to drop the stern drive and replace the impeller if it
comes down to that?

I have a Mercruiser O.E. service manual. I cannot find any procedures
or specifications for checking coolant flow at any point on the engine.
Is there a test port? If there is, does anyone know the
specifications related to coolant flow? I am going to go ahead and
replace the impeller located in the stern; however, I have a sneaking
suspicion that I will remove the unit and find no damage. My factory
service manual does not provide a test procedure for the engine temp
sensor. Does anyone know what it is. I would assume that it is likely
a resistence test. Before I go to the length of dropping the stern
drive, I want to rule out all other possibilities. I really appreciate
all of the advice. I had an impeller fail on a boat with a 5.7 L Bravo
set-up, and it was not like this. It was obvious no water was being
drawn up at that point. Like I mentioned, when I removed the
circualtion pump and hoses water poured out from all directions.

But is it pumping enough volume???

That was exactly problem with my friends mastercraft. He could idle around
and maybe get up to plane speed...some water was getting thru. When he
tried to tow a tube or wakeboard, it overheated right away. Completely
clogged, and it would have overheated at idle as well.

--Mike

"Lost In Space/Woodchuck" wrote in message
...
But is it pumping enough volume???


"Weldo60" wrote in message
ups.com...
I have thought of that. My Dad had the exact same problem with his
Mariah. What causes me to doubt that scenario is the fact that I am
getting water into the engine. I popped one of the plugs off of the
port manifold and ran the engine while in the water, and water shot out
of the plug for five minutes after the engine was shut down. I just
hate to drop my stern drive if that is not the problem; however, I am
running out of other options. Which brings me to my next question.
How hard is it to drop the stern drive and replace the impeller if it
comes down to that?