Hello All,

I recently purchased a boat with a ~1986 Mercruiser 170 (inline 4). It
ran fine and cool when tested before purchase.

Now that I have it home, I fired it up for the first time in the yard.
It fired fine and ran smooth, but started to overheat within about a
minute or so. I turned it off before it reached 200. I noticed that it
was not outputting any water out from the gimble area of the outdrive.
When tested before purchase, there was significant water coming from
that area.

This leads me to belive that the raw water pump in the outdrive is not
functioning properly. To test this theory I disconnected the hose
leading from the outdrive from the heat exchanger. I then restarted
the engine and let it run for about 30 seconds. No water came fom the
hose.

This still leads me to believe that it is the outdrive water pump. Odd
thing is, the seller told me that the water pump had recently been
rebuilt. He even commented during the pre-purchase how good the outlet
flow was, and I agreed.

So I guess my question is... if I am not getting water from the hose
into the heat exchanger, is it definitely the water pump? Can the
voltage regulator interfere with the flow? (it is between the outdrive
and the exchanger). Is there any other way to test the raw water
pump?

BTW, I did check the water inlet area of the outdrive and it looks
clean. The earmuffs are making good contact and there is good water
pressure from the hose.

Thank you for your assisatnce!

John

"JT" wrote in message
ups.com...
| Hello All,
|
| I recently purchased a boat with a ~1986 Mercruiser 170 (inline 4). It
| ran fine and cool when tested before purchase.
|
| Now that I have it home, I fired it up for the first time in the yard.
| It fired fine and ran smooth, but started to overheat within about a
| minute or so. I turned it off before it reached 200. I noticed that it
| was not outputting any water out from the gimble area of the outdrive.
| When tested before purchase, there was significant water coming from
| that area.
|
| This leads me to belive that the raw water pump in the outdrive is not
| functioning properly. To test this theory I disconnected the hose
| leading from the outdrive from the heat exchanger. I then restarted
| the engine and let it run for about 30 seconds. No water came fom the
| hose.
|
| This still leads me to believe that it is the outdrive water pump. Odd
| thing is, the seller told me that the water pump had recently been
| rebuilt. He even commented during the pre-purchase how good the outlet
| flow was, and I agreed.
|
| So I guess my question is... if I am not getting water from the hose
| into the heat exchanger, is it definitely the water pump? Can the
| voltage regulator interfere with the flow? (it is between the outdrive
| and the exchanger). Is there any other way to test the raw water
| pump?
|
| BTW, I did check the water inlet area of the outdrive and it looks
| clean. The earmuffs are making good contact and there is good water
| pressure from the hose.
|
| Thank you for your assisatnce!
|
| John
|
Did anyone run the engine without the water supply? It only takes a few
seconds to destroy the impeller.

Did anyone run the engine without the water supply? It only takes a few
seconds to destroy the impeller.

Not since I saw it running fine before I bought it. This was the first
time I ran it, and the earmuffs were proving plenty of water. Any
other ideas?

Yeah, someone fired it up without the muffs. If not you, who? Did you
take possession of the boat and tow it off directly after the run-up at
the seller's place? Or later?
JR

JT wrote:

Did anyone run the engine without the water supply? It only takes a few
seconds to destroy the impeller.


Not since I saw it running fine before I bought it. This was the first
time I ran it, and the earmuffs were proving plenty of water. Any
other ideas?



--
--------------------------------------------------------------
Home Page: http://www.seanet.com/~jasonrnorth

Yeah, someone fired it up without the muffs. If not you, who? Did you
take possession of the boat and tow it off directly after the run-up at
the seller's place? Or later?

I bought the boat immediately after running the engine... hooked it up
to my truck and drove away. I'm not saying it's not the impeller, but
it doesn't make sense that it would die just like that. Like I said,
it was working perfectly just minutes before I drove it home.

So back to oe of my original questions... if I'm not getting water at
the inlet hose to the heat exchanger, can it ONLY be the impeller/
pump, or can anything between the pump and exchanger cause this?

Thanks for your assistance!

On Jul 8, 10:04 pm, JT wrote:
Yeah, someone fired it up without the muffs. If not you, who? Did you
take possession of the boat and tow it off directly after the run-up at
the seller's place? Or later?

I bought the boat immediately after running the engine... hooked it up
to my truck and drove away. I'm not saying it's not the impeller, but
it doesn't make sense that it would die just like that. Like I said,
it was working perfectly just minutes before I drove it home.

So back to oe of my original questions... if I'm not getting water at
the inlet hose to the heat exchanger, can it ONLY be the impeller/
pump, or can anything between the pump and exchanger cause this?

Thanks for your assistance!

The line may pass through a power steering cooler before the heat
exchanger. I've never seen those be a problem though. Basically the
impeller sits just above the inlets where you put the muffs. The
water goes up from that and thru the transom. I have seen hoses
delaminate inside and stop up even thoug they looked ok from the
outside but that is also pretty rare. You could disconnect the hose
at the inside of the transom and see if you get any water there. It
is hard to reach but not impossible on most boats. If there is still
no water then you need to drop the lower unit and look at the impeller.