Hunter 34 Yanmar 3gmf

R

Randy Church

.
Feb 28, 2006
81
Hunter 34 610 Narragansett Bay
Yanmar 3gmf owners.

Spring start up here in Rhode Island.
Is it necessary to clean the heat exchanger on this engine?
My RPM gauge works and then it stops.
Anyone have any experience with either of these?

Thank you,
Randy
 
Tom J

Tom J

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Sep 30, 2008
2,323
Catalina 310 Quincy, MA
Any heat exchanger should be cleaned periodically. You can take it to a radiator shop for cleaning, and get it pressure tested at the same time. What kind of tach do you have? If it is fed from the alternator, you can sometimes turn the calibration screw on the back of the tach, back and forth a few times to get the tach working again. Be sure to mark the spot where the screw is set, and return it there. This is usually a temporary fix.
 
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kloudie1

kloudie1

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Nov 6, 2006
10,055
Hunter 34 Mandeville Louisiana
Randy, I wouldn't open the heat exchanger unless you suspect fouling or have overheating. If the boat is new to you, it may be prudent to open the forward end cover and remove any impeller vanes that you may find. If done very carefully, you won't need a new gasket or o-ring, but again it would be prudent to have those on hand.. The tachometer is driven by a sensor that counts teeth on the flywheel and converts that to RPM. That sensor is aft/port on the engine. the connectors for the wires are notoriously intermittent/dirty and need to be cleaned when the tacho gets squirrelly. Attached is a wiring diagram showing the sensor (bottom left) and its wiring. Also attached is a photo showing the wires location on the engine. In the picture you can see the orange and blue/red wires just aft and below the fuel injector.
Engine Port Aft.JPGYANMAR GM Wiring.jpg
 
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F

flightlead404

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Apr 2, 2021
416
Hunter 38 On the move
I have to remove my heat exchanger end caps on my 3JH4E soon. They are mounted with round socket (Allen) head cap screws. When I tried to remove them a few months ago they didn't budge and the socket started to round, so I stopped.

Can anyone recommend a tool that can remove these cap screws? I don't want to have to resort to drilling them out.
 
I

ice breaker

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Sep 11, 2011
419
Hunter 41AC Bayfield WI, Lake Superior
Funny story. Last August on a hot no wind day hanging on the hook, I was bored and decided to back flush my Panda gen set. The gen was and is running fine. So I back flush the raw water line and I get almost enough impeller fins to make a whole impeller. So next is the yanmar. Big back flush and no pieces came out.

I expected a few out of the panda as early in its life it ate impellers at an alarming rate.

Some times it pays to get bored enough to do maintenance..................
 
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DeniseO30

DeniseO30

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Feb 26, 2009
716
Oday 30 Anchor Yacht Club, Bristol PA
Randy Church said:
Yanmar 3gmf owners.

Spring start up here in Rhode Island.
Is it necessary to clean the heat exchanger on this engine?
My RPM gauge works and then it stops.
Anyone have any experience with either of these?

Thank you,
Randy
Click to expand
I would not suggest you not,start diving into taking things apart or taking off the heat exchanger,

suggestion, do the simple things first, the impeller, determine if the water circuit through the exhaust elbow is running freely from the roads pump, check the exhaust elbow if ifhas never been changed it's probably just blocked or partially clogged,
far as I know the RPM gauge (tachometer) is a hall effect in other words it has a sensor on the flywheel teeth, I but I also have determined from many hours of reading is all Yanmar tachometers are "off" good luck
 
DeniseO30

DeniseO30

.
Feb 26, 2009
716
Oday 30 Anchor Yacht Club, Bristol PA
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