How to pressure test a 4.3 l mercruiser

[sprizzel]

Hello everyone,

I want to pressure test the water jacket/cooling system of my 4.3 l mercruiser engine for leaks/cracks. I have spent weeks trying to find a clear cut way to do this. I am unsure of what hoses need to be plugged. I appreciate the help in advance.

 

[tpenfield]

Post the serial number to your engine, as the cooling systems do vary a bit. A few pictures of the engine would be good to see as well.

Also decide If you want/need to include the exhaust manifolds in the test, or if it is just the engine block.

Tell us a bit of background that is leading you to doing a test.

Generally speaking, for the engine block test you will want to block the incoming water connection at the thermostat housing and the hoses either leading to the exhaust.

 

[Scott Danforth]

there are about 20 variations of the 4.3 since 1985

however assuming you have a raw water cooled 4.3, take the inlet hose from the power steering cooler to the thermostat housing and block off that port. take the 2 or 4 lines going to the exhaust manifolds and elbows and block tee them together and add pressure and a gauge there.

exhaust manifolds have to be tested with the acetone test, or you have to fabricate block-off plates.

 

[Bondo]

Ayuh,.... 'n drain the water out, before you put the air to it,....

 

[sprizzel]

Serial number is 1A050350. I had my boat sit for awhile and want to ensure no cracks. I don’t see any outside crack but want to ensure for my peace of mind. TIA

 

[sprizzel]

Serial number is 1A050350. I had my boat sit for awhile and want to ensure no cracks. I don’t see any outside crack but want to ensure for my peace of mind. TIA

 

[markhodges78]

I think I noted everything correctly

 

[sprizzel]

I think I noted everything correctly

 

[sprizzel]

Thank you so much! I’ll try this

 

[Scott06]

Serial number is 1A050350. I had my boat sit for awhile and want to ensure no cracks. I don’t see any outside crack but want to ensure for my peace of mind. TIA

How was it winterized? If it was drained u will have no issue

 

[markhodges78]

Thank you so much! I’ll try this

No problem

 

[sprizzel]

How was it winterized? If it was drained u will have no issue

Well I bought the boat from someone else and doing it as a project. They “say” it was winterized properly but I don’t trust it. I pulled the spark plugs and water came out one of the cylinders.

 

[Scott06]

Well I bought the boat from someone else and doing it as a project. They “say” it was winterized properly but I don’t trust it. I pulled the spark plugs and water came out one of the cylinders.

Ahh, thats not good. Did it turn over freely. Would check outside of block and exhaust manifolds. Could have gotten down carb but not a great start.
if you run into an issue a vortec 4.3 out of wrecking yard is an easy swap over