[C320-list] Vibration at 1000 RPMs and Perkins Injectors?

[mark]

Rollie,

You say the smoke is grey.  Most of what I've read and seen about smoke from a diesel exhaust describes it as white, blue or black.  Each means something different.  White smoke would usually mean either steam or unburned atomized diesel.  If the white smoke smells like unburned diesel oil, and leaves a sheen on the water around the exhaust, it's more likely diesel than steam.  Blue smoke usually means you're burning engine oil, and black smoke usually is caused by soot from partially burnt diesel.  Grey sounds like it could be a little bit of any of those.

The Perkins should be able to get to 3,400 - 3,600 rpm, even under load.  What happens if you add more throttle after you get to 2,700RPM?  If the smoke from the exhaust turns darker, or black, it means the governor is causing the injector pump to add more fuel at the injectors, but the engine can't burn it all.  That would suggest either the prop is fouled (as Michael suggested) or that the engine is losing power for reasons other than fuel starvation.  (Like a lack of compression.)  Is your boat speed lower at 2,700RPM than it used to be?  That would sound more like a fouled prop.  If not, a compression test would tell whether the valves and rings are doing their job.  But I have had no luck finding anyone to run a compression test on my Perkins, or even finding out what adapter would be needed to run a compression test if I bought the tester myself.  (2 Perkins dealers have told me they have no idea what adapter I'd need, and the adapters themselves are sold based on what kind of truck engine they fit.)

If the engine doesn't speed up when you try to add more throttle, but the smoke doesn't change, that would suggest that the injection pump and injectors can't inject enough fuel to go any faster.  In that case I would try testing or rebuilding those components.

Hope this helps with your diagnosis.  Let us know what it turns out to be, because that's how we all learn what to look for when our boats act up.

Mark Seyler
S/V Reality,
Catalina 320, #232
New Orleans, LA



-----Original Message-----
From: C320-list [mailto:c320-list-bounces at lists.catalina320.com] On Behalf Of Dave Hupe
Sent: Saturday, December 12, 2020 9:48 AM
To: C320-List at Catalina320.com
Subject: Re: [C320-list] Vibration at 1000 RPMs and Perkins Injectors?

 If you pull the exhaust elbow, as Jeff mentions, the short wet exhaust hose to the muffler likely will be rigid and need to be cut out and replaced.  Jeff and I both suggest replacing it with the hump hose from Catalina direct Exhaust Hump Hose 2" I.D. x 6" (catalinadirect.com) and the 2 inch fiberglass splice Exhaust Hose Fiberglass Splice for 2" Hose (catalinadirect.com). You also will need a short piece of regular wet exhaust hose and lots of clamps to splice enough hose length together between the exhaust elbow and muffler (even though the total length is I think less than 1 foot total).  Using the hump hose is good to reduce vibration on the inlet fiberglass flange of the muffler. Dave Hupe
1994 C320 (#32) with Perkins M30
Holland, MI