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MC-1

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landhort

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I recently bought a 1975 StarCraft Islander 22 powered by an inline 6 165. I’ve identified the outdrive as the Mercruiser MC-1. This boat has not been in the water for a number of years and I took the motor, gimbal housing and outdrive off to replace the rotten wooden transom. Now it’s time to put it back together. In the process of learning/finding all the parts/tests that I need to do this properly, I came across the need to ‘pressure test’ the lower unit before final assembly. Can someone explain how to do this and what the resulting pressure should be?
 
A mercruiser out drive when operational/ running will produce about 7-9 psi.

To check for seal integrity, A pressure test can be performed.
There is a drain plug at bottom of drive near the cone and should be one on the side near the top of drive, both being on the same side of the drive ( looking transom from outside and at the rear of the bost, that would be on the left)

1. Remove both plugs and Drain gear oil from drive as test must be done with drive pretty much empty.

2. you need a threaded adaptor that matches the plug thread and a hand pump with a gauge that can read up to 30psi or a little higher.

3. Reinstall one plug back into drive (top or bottom doesnt matter)

4. Thread in hand pump and pump to 12-15 psi and outdive should hold that pressure for 1-2 minutes with no loss in PSI.

If it leaks you should be able to hear it and it must be repaired.

Look up Stevens Pressure checker on google to see what one looks like. Any type will work but that one is what most shops use.
 
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kghost said:
A mercruiser out drive when operational/ running will produce about 7-9 psi.

To check for seal integrity, A pressure test can be performed.
There is a drain plug at bottom of drive near the cone and should be one on the side near the top of drive, both being on the same side of the drive ( looking transom from outside and at the rear of the bost, that would be on the left)

1. Remove both plugs and Drain gear oil from drive as test must be done with drive pretty much empty.

2. you need a threaded adaptor that matches the plug thread and a hand pump with a gauge that can read up to 30psi or a little higher.

3. Reinstall one plug back into drive (top or bottom doesnt matter)

4. Thread in hand pump and pump to 12-15 psi and outdive should hold that pressure for 1-2 minutes with no loss in PSI.

If it leaks you should be able to hear it and it must be repaired.

Look up Stevens Pressure checker on google to see what one looks like. Any type will work but that one is what most shops use.
Click to expand...
Thanks kghost, that explains it perfectly. Seems straightforward and simple.
 
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