Boxxer 421 Exchangers

[tman7]

Is anyone familiar with how much heat the exhangers contribute to the over all heat? Specifically how much heat would be lost if the engine exhaust exchanger got clogged, which seems to be what I am experiencing. I get just a bit over 100 degrees. (From the blower exchanger?) The casing of the Xchanger gets plenty hot but just doesnt seem to transfer to water temp. Yes, the diverter is working - no exhaust coming out when in heat mode.

Perhaps a build up of carbon? Not sure how to tackle this. Seafoam? Almost afraid to put some directly into the Briggs engine; afraid of what it might do to the blower exchanger or something in the exhaust path. Thanks for any suggestions.

 

[Chris A]

Id just take it to your disty and have them clean the hx, that or maybe your dema valve is stuck open? I had both issues when I first bought mine.

 

[tman7]

Looks like

Found the problem or at least a large part of it. Took off the divertor/exchanger shield and voila, seals and or gaskets at the divertor mechinism are toast. Has nice gaps on both sides spewing exhaust that would otherwise be entering the exchanger. Should be pretty simple fix. Hope its the ONLY source of the lost heat. Strange thing is it seemed to happen very quickly.

 

[Shawn Forsythe]

It is awfully important to have the exhaust back-pressure periodically checked on a Boxxer 421. Any heat problem suspecting an HX issue is a real red flag, regardless of issue you found. It is indeed possible that those gaskets failed in part to excess pressure. The next symptom could be serious/expensive engine problems.

Recent vintage 421's have a port on the exhaust manifold specifically for checking the pressure quickly and easily.

 

[tman7]

Shawn, I have a couple questions for you. Don't know if you can tell from the photos attached but the exhaust manifolds where they connect to the divertor appear to have warped or bowed slightly. (On both ends) I'm wondering do I have a more serious problem then I think. If they are warped then new gaskets may not seal. What would be a possible source of excessive back pressure for the exhaust system? Clogged muffler? The exhaust from muffler does not seem to have changed any. Thanks for your thoughts.

View attachment 3614View attachment 3615