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Yanmar 3ym20, glow plug option?

Apr 20, 2020
Catalina 309 92 South Haven, mi
I have a 2007 Catalina 309 that I just purchased last year. My Yanmar 3ym20 manual suggests there is a glow plug position on the key ignition switch. Nothing is marked on the panel. My switch does not turn to the left (for glow plug) as the manual suggests. I have found a couple of ignition switches in the previous owners "spare parts" inventory. Is it possible that it requires a specific switch to use the glow plug option and that the PO purchased the wrong switch?

I did find that when cooler fall temperatures occured that it was harder to start my engine. Prior to that it started easily.

I am a new boat owner that's just trying to figure out things on his "new" boat. I've looked at some forums and posts that give conflicting information feedback on this issue. Some say Yanmar's don't have glow plugs in them, ever...??? Thanks in advance for any direction/suggestions you may have.
Feb 21, 2013
Hunter 46 Point Richmond, CA
One 3ym20 Yanmar engine manual says a glow plug is there, if equipped. Below is an excerpt from 2 different 3ym20 engine manuals I found on line on starting the engine with and without a glow plug and starting in cold temperature with a glow plug. Do you have a "glow plug switch", if not, engine start as the operation manual excerpt on the left indicates.

Jan 22, 2008
Beneteau 323 Annapolis MD
My 3YM20 Benny came with the rotary ignition, with the glow plug feature. I can start the engine all winter (above zero) without the glow plugs. I doubt it take 5 seconds of cranking to start.
Jun 4, 2009
Catalina 309 Swantown Marina Olympia, WA
My 2006 309 came with a glow plug position on the switch but the switch gave out after about a month and Catalina replaced it with a new one that did not have the glow plug position. I had the boat for 12 years and had no problem starting it even in below freezing temps.
Aug 21, 2019
Catalina 315 Grosse Pointe Park, MI
The glow plug seems to be a mystery on my 315 as well. It is similar to a 309 and has a Yanmar 3YM20. I can see that there are, in fact, glow plugs on the engine. But, in the glow plug position of the key, I can not detect any current usage on my panel. In anycase, the engine starts up easily without it.
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Apr 13, 2015
Catalina 309 Tampa
On my 309, the key switch rotates past the on position for glow. Even in FL I use a few seconds of that in dead winter and it helps. I don't have any second key...just the one.

Dave in Port Charlotte