Heat Exchanger blocked: recommendations how to flush or unclog?

[Adnieder15]

I replaced the heat exchanger end gasket this spring after I saw the old one had disintegrated and left small rubber pieces within the heat exchanger. I removed all the pieces I could, installed the new gasket, and everything seemed fine. I drove the boat today and noticed the engine temp was very high. I suspect there is minimal or now water flowing through the heat exchanger, and after I removed the cap and gasket it was very dry.

Any suggestions how to back-flush or troubleshoot if I suspect there's still a piece of the old gasket blocking flow?

 

[Scott Danforth]

Pull the end caps off. Get a piece of 1/8" aluminum rod and push the debris out of each tube.

 

[dubs283]

I suspect there is minimal or now water flowing through the heat exchanger, and after I removed the cap and gasket it was very dry.

What engine is this? Model/serial number?

Have you inspected/replaced the sea water pump impeller?

 

[Adnieder15]

What engine is this? Model/serial number?

Have you inspected/replaced the sea water pump impeller?

Sorry--Mercruiser 170. The water pump impeller were replaced less than 12 months ago.

 

[Adnieder15]

Pull the end caps off. Get a piece of 1/8" aluminum rod and push the debris out of each tube.

Removed the end caps and used a rod to clear the exchanger--no debris. Also was able to remove the inlet / outlet water hoses and flush--no obstructions.

Since I'm testing this in my driveway with a pressurized water hose, it's hard to tell if the impeller is the issue or not.

Any suggestions how to confirm if the impeller is the culprit when the boat is trailered?

 

[tank1949]

Removed the end caps and used a rod to clear the exchanger--no debris. Also was able to remove the inlet / outlet water hoses and flush--no obstructions.

Since I'm testing this in my driveway with a pressurized water hose, it's hard to tell if the impeller is the issue or not.

Any suggestions how to confirm if the impeller is the culprit when the boat is trailered?

My Bravos had crank water pickup pumps and were easy to access and replaced impellers before I went inside, HE. I suspected former owner never rodded out HE because I did find small impeller debris in a few of the HX holes. I rodded out and then use air hose to remove most of the rest.

 

[Scott Danforth]

Any suggestions how to confirm if the impeller is the culprit when the boat is trailered?

You should be replacing the impeller ever few years and removing as part of winterizing

 

[Scott06]

You should be replacing the impeller ever few years and removing as part of winterizing

On an alpha drive there is no need to split the drive and remove the impeller for winterizing .

to the OP i would check the water flow to the heat exchanger when in the water. Also use OEM impellers they last much longer than the aftermarket ones. i would suspect if u have low water flow u lost a vane on the impeller and it blocking water flow out of the pump. happened to me, put the boat in the water in the spring worked perfectly next time i took it out it got hot, absolutely zero flow out of the pump vane was laying on its side blocking the outlet.

 

[Scott Danforth]

On an alpha drive there is no need to split the drive and remove the impeller for winterizing .

There is no factory Heat exchanger cooled alpha drive setups as Mercruiser determined the pump in an alpha is too weak to pump thru a heat exchanger. Any dealer conversions have a second pickup and a Bravo pump bolted the the front and the alpha pump just keeps the drive cool

 

[Scott06]

There is no factory Heat exchanger cooled alpha drive setups as Mercruiser determined the pump in an alpha is too weak to pump thru a heat exchanger. Any dealer conversions have a second pickup and a Bravo pump bolted the the front and the alpha pump just keeps the drive cool

Did not think the 3.7 tgat he is talking about came with belt driven pumps

 

[ROY WILLIAMS]

Removed the end caps and used a rod to clear the exchanger--no debris. Also was able to remove the inlet / outlet water hoses and flush--no obstructions.

Since I'm testing this in my driveway with a pressurized water hose, it's hard to tell if the impeller is the issue or not.

Any suggestions how to confirm if the impeller is the culprit when the boat is trailered?

the heat exchanger of the coolant antifreeze also the engine antifreeze . the T stat is the antifreeze ...also the outdrive of that impeller is the correct water of the higher fluid next to the propeller ..did the driveway of the water hose working ...muffs ........
also the exhaust elbow inspected it ..

 

[dubs283]

There is no factory Heat exchanger cooled alpha drive setups as Mercruiser determined the pump in an alpha is too weak to pump thru a heat exchanger.

470

 

[Scott Danforth]

470

Technically released with MC drive

 

[Scott06]

Technically released with MC drive

the 470 and the rest of the engines in its 3.7 L family produced from 1976 thru 1989 would have been paired with MC1, R, MR, and alpha gen one drives. All use pretty much the same water pump, probably why they were prone to overheat

 

[dubs283]

There is no factory Heat exchanger cooled alpha drive setups as Mercruiser

Alpha one/mr/r/mc-1 (all) use the same impeller/sea water pump housing

Only caveat being is w/p base/seal assy.

If you'd like to get more esoteric I'm free to chat

As Scott06 mentions, the colloquially known 470 was produced until the 1989 season which includes a vast number of alpha ones

We've yet to determine which closed cooled version of alpha/sbc/mercruiser (assuming) OP has in possession but I'm quite confident there's many alpha one closed cooled oem products still around

 

[nola mike]

Alpha one/mr/r/mc-1 (all) use the same impeller/sea water pump housing

Only caveat being is w/p base/seal assy.

If you'd like to get more esoteric I'm free to chat

As Scott06 mentions, the colloquially known 470 was produced until the 1989 season which includes a vast number of alpha ones

We've yet to determine which closed cooled version of alpha/sbc/mercruiser (assuming) OP has in possession but I'm quite confident there's many alpha one closed cooled oem products still around

He said he's got a 170, which is the 1985/86 3.7l. paired with an a1g1 and full OEM closed cooling. Only pump is in the drive, as mentioned.

 

[tank1949]

On an alpha drive there is no need to split the drive and remove the impeller for winterizing .

to the OP i would check the water flow to the heat exchanger when in the water. Also use OEM impellers they last much longer than the aftermarket ones. i would suspect if u have low water flow u lost a vane on the impeller and it blocking water flow out of the pump. happened to me, put the boat in the water in the spring worked perfectly next time i took it out it got hot, absolutely zero flow out of the pump vane was laying on its side blocking the outlet.

and stay away from sandy beaches where u suck sand into impeller. almost impossible in NW Florida.

 

[ROY WILLIAMS]

and stay away from sandy beaches where u suck sand into impeller. almost impossible in NW Florida.

well the outdrive is the impeller of the sand in the water ... flush it out of the engine / heat exchanger also the elbow exhaust ...take the plugs out flush ..