Re: Homemade Lower unit tester
Yes they said the shop manuals say that. But the mercury tech manuals from merc dont. So Im not sure as i never seen an original tech manual.
The Mercury OB manuals do show a pressure test, but nothing about a vacuum test. Mercruiser OEM service manuals don't even talk about a pressure test, let along a vacuum test. They can be done, but on Mercruiser the input shaft seal is a one way seal (as mentioned earlier) and will not hold much vacuum at all before sucking air. I feel lucky if I can get between 5 and 10 inches of vacuum.
The vacuum test however, will not damage anything. I have used it several times to find problem leaks. It helps if you have a pivoting drive stand so you can fill the input shaft seal of the Mercruiser drives with thick gear oil so you can find leaks from other places because the heavy oil prevents the input shaft from leaking (Until the oil is gone).
Personally, I would use a hose to hook it to the drive. If leaks was my concern, I sure wouldn't have used teflon tape on my fittings, and when hooked to the drive and pressurized, check the gauge fittings and connections with soapy water, just like you do the drive.
