Yanmar 2GM fuel system calibration

E

efair

.
Nov 9, 2016
4
Hunter 33 Atlanta
Our newly-acquired H33 has the subject engine. It starts and idles fine, but with the throttle lever at full speed it only turns 1600RPM. It runs smoothly, no smoke, but I know it's supposed to turn at ~3600 RPM.

The manual shows two adjustments related to fuel, but says they are set at the factory, locked with wire, and lead soldered in place. The manual shows no calibration or adjudgment procedures anywhere. I see the wire is missing.

Does anybody know (or does anybody's grandfather know) the steps to reset to baseline, and to tune to final?
 
Tally Ho

Tally Ho

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Jan 7, 2011
5,431
Oday 322 East Chicago, IN
efair said:
Our newly-acquired H33 has the subject engine. It starts and idles fine, but with the throttle lever at full speed it only turns 1600RPM. It runs smoothly, no smoke, but I know it's supposed to turn at ~3600 RPM.

The manual shows two adjustments related to fuel, but says they are set at the factory, locked with wire, and lead soldered in place. The manual shows no calibration or adjudgment procedures anywhere. I see the wire is missing.

Does anybody know (or does anybody's grandfather know) the steps to reset to baseline, and to tune to final?
Click to expand
Are you getting 1600 RPM’s in neutral or with the transmission engaged? If the later, how clean is the prop and the bottom of the boat?

It could be the fuel cable is not actuating completely. This would be easy to test….just find the throttle lever on the engine and try moving it manually to get past 1600 RPMs…even in neutral at the dock.

I can’t help with setting the fuel adjustments. I have had my 2GM20F engine for 10 years and have never needed to adjust (not even sure it is possible for mere mortals).

Greg
 
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Alan Gomes

Alan Gomes

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Nov 22, 2011
1,246
Ericson 26-2 San Pedro, CA
Don't mess with those two adjustments that are wired shut as you can royally screw up your engine if you do. And besides, it's not likely that this is your problem anyway.

The first thing you should do is purchase an inexpensive optical tach from Harbor Freight or online at Amazon. This will let you know what RPM the engine is REALLY turning vs. what your tach is showing. (The tach *could* be way off.) Then, as has been suggested, see whether you hit top RPM in neutral. Then go from there, checking your throttle cable, exhaust elbow for blockage, clogged fuel filter, etc.--the usual suspects.
 
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JoeWhite

JoeWhite

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Mar 6, 2008
1,290
Catalina 1999 C36 MKII #1787 Coyote Point Marina, CA.
As Alen pointed out, I vote for blocked primary filter. If it has viewable tray look to see if there is enough fuel in it when running at high RPM.
 
Alan Gomes

Alan Gomes

.
Nov 22, 2011
1,246
Ericson 26-2 San Pedro, CA
JoeWhite said:
As Alen pointed out, I vote for blocked primary filter. If it has viewable tray look to see if there is enough fuel in it when running at high RPM.
Click to expand
Or, just change it, since that probably should be done anyway. Since the boat is newly acquired, I'd do all of the regular maintenance on it right now, so you know that you are starting from a good, known condition for oil, filters, impeller, exhaust elbow, etc.
 
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Ralph Johnstone

Ralph Johnstone

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Jan 4, 2006
7,148
Hunter 310 West Vancouver, B.C.
Alan Gomes said:
Don't mess with those two adjustments that are wired shut as you can royally screw up your engine if you do.
Click to expand
I think what @Alan Gomes said is worth repeating. Unless as you've said :

efair said:
I see the wire is missing.
Click to expand
Maybe your engine has already been royally copulated. I managed to knock the seal wire off mine with a heavy wrench, so maybe assume yours has suffered the same indignity and ignore for now. Proceed as already suggested.
 
E

efair

.
Nov 9, 2016
4
Hunter 33 Atlanta
Thanks for all the replies so far. We did perform an engine service, including replacement of both fuel filters, prior to starting the engine. The 1600 RPM limit is both in neutral and with the transmission engaged.

We will confirm the full range of travel for the fuel control lever on the engine at at our next opportunity. I presume that means confirming that the movement on the engine end corresponds to the movement at the helm throughout the full range, if I'm wrong there please correct me.
 
Ralph Johnstone

Ralph Johnstone

.
Jan 4, 2006
7,148
Hunter 310 West Vancouver, B.C.
efair said:
if I'm wrong there please correct me.
Click to expand
Yes, that is correct.
Or maybe just to remove all doubt, disconnect the cable and crank the throttle lever (yes, I know that's wrong) as far as it will go.
 
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Dalliance

Dalliance

.
Oct 6, 2007
1,118
Hunter H30 1982 Chicago IL
I have the same 2GM engine. The Yanmar engine panel tachometers are notoriously inaccurate. As Alan suggested, buy yourself a hand held laser tachometer and see what your actual RPM’s are. Mine was about $15 from Amazon and it showed my Yanmar tach was reading 25% low. My actual max RPM was still below spec, but much closer.
After ruling out all other issues: messed up adjustments, fuel filters, exhaust elbow, compression issues, etc., there is one more possibility that I stumbled onto last summer. I don’t know how common this is, but when my 42 year old fuel lift pump failed and was replaced in August, my actual max RPM, as read by the handheld tach, was suddenly up to spec. The engine had apparently not been getting enough fuel for years because the lift pump was no longer performing at full capacity.
 
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