New owner - tachometer jumping around,Intermittent

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Tsoman
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Joined: 4/15/24
Posts: 2
New owner - tachometer jumping around,Intermittent

Hello 
I am a new owner of a 1994 Catalina 36. I bought it last September and sailed it a few times before I winterized it and had it hauled out for the winter. Before I bought it, I had an inspection done and the boat and engine were in great condition.

It's back in the water now and I went sailing last Sunday. It was kind of rough, around 25 knots of wind  and choppy, but I noticed when we were motoring out, when I gave it throttle, the RPM's displayed on the tachometer were jumping around. I could not hear any difference in engine speed and I couldn't feel any loss or surge in power. The needle would move a few notches up and down once or twice per second. The voltage reading stayed consistent right in the middle. 

after I ran the engine for a while, it stopped doing this. 

Do you think this is probably an issue with the tachometer itself, or a loose connection? I am hoping to use the boat, but I don't know if I should get this addressed first. Seems kinda minor but I really don't want to get stranded.

If it could be a connection issue, could someone tell me where to look to possibly tighten it up and see if that helps?

also, when I had the engine serviced recently, the technician noted that the alternator was mounted wrong. $500 to remount it correctly. Could there be a connection here?

thank you
 

 

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Haro
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Joined: 11/7/14
Posts: 420

I do not know where to start my experience. When I bought my c36, it had a broken wire on the alternator that made the tach stop working. This wire is on the back of the alternator and it is listed in the manual for your engine.
The real problem was a cracked alternator bracket causing excess engine vibration which broke the wire.
Then on a long engine cruise the bracket broke and the alternator was hanging from its front bracket. This caused loose belt and inconsistent tach reading.
The only other reason is that the regulator turns off charging the batteries since the batteries have reached full charge. This happens if you have solar panel.
To test this condition turn on the fridge compressor and the regulator will start charging and your tach will be steady.
While you ate working on the alternator,  install a #8 stranded wire from the ground lug of the alternator to the shunt on the non-battery side. This will prevent damage to the alternator due to loss of ground, as the hinge bolts do not provide reliable ground.
Save your money,  do the work yourself if you would like to have it done right.
Read more on my website listed on my signature.

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pkeyser
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Joined: 5/18/13
Posts: 668

You might also open the instrument pod and jiggle some wires with the engine running. The tach likely has a small slotted disc on the backside of the housing. This is a potentiometer that can be rotated back and forth to calibrate the tach. Try turning it back and forth a couple of times and then return it to the original position. Internal corrosion is common to this part and can create tach issues. "Exercising" it removes the corrosion.   

Paul & Wendy Keyser
"First Light"
Rye NH
2005 C36 MKII #2257
Wing, M35B

Tsoman
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Joined: 4/15/24
Posts: 2

Thank you both! I'm going down to the boat today to work on another project of replacing a leaky potable water hose. I will take a look at the alternator and take a picture of how it's mounted. I also noticed that my blower does not seem to be turning on. I don't remember if it was working last year or not.

dhickmanii
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Joined: 7/27/18
Posts: 32

I would also add there there is a screw in the back of the tach to adjust it for different alternators. If it wiggles too freely, it can cause erratic tach needle movements. Usually from working to not working. It's the one that has the gauge marks around it.  Either A, B,C,D or 1,2,3,4.  I can't remember which. 

David
Mobile, AL
S/V Beach Belle
1983 Catalina 36 Mk I #154

Std. Rig, Fin Keel, M25

Army Sailor
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Joined: 11/2/23
Posts: 8

Thanks for the info on the solar panels.  I replaced the entire charging system on my boat when if fried the first day I was sailing it.  Since that time, the tach would work for awhile then shut down.  It does connect to the regulator, so and I do have solar panels, so that could certainly explain why it turns itself off after awhile.  I always thought it was some kind of regulator setting I couldn't figure out.

It never worried me that much as it seems pretty hard to run my engine much over 2200 RPM anyway.  The throttle starts to hit the console above that.

Lanealoha
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Joined: 2/13/20
Posts: 79

My experience was much like Haro explained.  Cruising down the coast of Baja last November, my wife was at the helm.  I awoke from a nap and asked her about the engine temp, she said it was fine, then I asked what RPM we were at and she said it says 0, 0!??  So I check the back of the tach, wires are solid, then I decide to see if I can follow the wire so I step down below and then I see oil flooding out from the engine compartment.  Kill the engine I yell!  Engine killed!  I open the engine compartment and as Haro noted above, the alternator bracket had snapped in 2 places and my alternator was dangling on the floor, after it managed to unscrew the oil filter and dump a Valdez-esque amount of oil on the cabin sole.  8 hours later we had the mess cleaned up, fashioned a splint for the alternator bracket out of an aluminum I Pad stand and then we were back on our way....the tachometer wire was disconnected from the alternator which is why it wasn't providing a readout.  About a week later the tach went out again, this time it was due to being chaffed through somewhere along the run so I replaced it all together.  Replace the alternator bracket before yours breaks, may be a lot cheaper to take the current bracket to someone to have it fabricated for you or spend $500 at Cat Direct...

David Lane
S/V Grace
88' Catalina 36'
Oxnard, Ca
 

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pkeyser
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Joined: 5/18/13
Posts: 668

Dave-
Do you have the M25 Engine? 

Paul & Wendy Keyser
"First Light"
Rye NH
2005 C36 MKII #2257
Wing, M35B

dhickmanii
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Joined: 7/27/18
Posts: 32

Yes.  Maybe you were talking to me. Too many Daves. 

David
Mobile, AL
S/V Beach Belle
1983 Catalina 36 Mk I #154

Std. Rig, Fin Keel, M25

Lanealoha
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Joined: 2/13/20
Posts: 79

This Dave also has the M 25 XP....

David Lane
S/V Grace
88' Catalina 36'
Oxnard, Ca
 

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