1990 Mercruiser 3.0 - PCV Valve

AaronHa

Recruit
Joined
Sep 18, 2019
Messages
3
Hi everyone,
Replaced carb and exhaust manifold and got the boat running over the course of a few months, but found that the PCV valve doesn't seem to have an input anymore on the new manifold. I jury-rigged a catch can, but found that the pressure needed ventilation, so I obliged and drilled some holes, but now I'm choking out the carb from clean air. I'm contemplating further jury-rigging of venting the catch-can to exhaust out an existing vent-hole.

Am I missing where the PCV input hole would be on the new manifold?
 

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alldodge

Moderator
Staff member
Joined
Mar 8, 2009
Messages
43,326
With it having that much blowby. I would suggest doing a compression and leak down test. My guess is the compression will be low, and the leak down test will tell where its leaking.
 

Pzilly

Cadet
Joined
Aug 29, 2019
Messages
13
Agree w alldodge that a comp and then leak test would be a good idea, I also remember seeing a bulletin about the PCV valve being eliminated on every thing except EFI model and that the standard hollow elbow should be installed with hose vented into the the spark arrestor. I would research that though its been awhile. Is the oil dipstick getting pushed out at all or oil coming out of the dip stick? Oil level staying constant and oil color?

I just found the crack in my cylinder, which started at first with just getting to much pressure out of the pcv, but shortly turned to water in the oil, hopefully yours is just a hose routing issue, if not good news is certified 3.0 long blocks are pretty cheap.
 

kenny nunez

Captain
Joined
Jun 20, 2017
Messages
3,462
The “blow by” that is coming from your engine is explosive, a carbon monoxide hazard and very dangerous. Most likely you have some stuck piston rings. The compression test and leak down procedure will prove it.
 
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