Correct engine RPM range

pbyrne · July 19, 2023, 12:47:13 PM

Quote from: Noah on July 19, 2023, 12:24:33 PM
No clue, I am not a mechanic. Others may respond with more helpful info. However, if your boat goes 6+ knots (confirmed by GPS in slack water) with tach reading 1600, I suspect your tach is reading incorrectly.

LOL. Fair enough.

Something else that came to mind is that the boat was just moved to a marina where we used the marina's fuel. Prior to that it was jerry can fed from Shell Gas Pumps. I'm thinking maybe I should consider the possibility the filters need changed.

Previously, they were changed infrequently from what I can tell. It was on my list for fall maintenance with the oil change for winterization.... but maybe it needs to be done now? Seems wierd that a top up ONCE would cause an issue with filters though...

Ron Hill · July 19, 2023, 03:11:54 PM

pby : If you are going 6 kts or more thru the water @1600rpm - right off the top of my head I'd say you have a bad tach!!!

Check it with your laser tach instrument!!

A few thoughts

KWKloeber · July 20, 2023, 02:01:07 PM

If the Tach is off before you trash it exercise the DIP switches or rotary switch setting. Contacts can become oxidized and produce false readings. There's troubleshooting for that in a manual for the gauges. If you don't find it on C34 Wiki I can probably find it elsewhere.

Ron Hill · July 20, 2023, 02:48:55 PM

pby : I believe that the tach range for your engine should be 0 to about 2800 rpm (maybe slightly more when not in gear!!) Idle should be about 1000 rpm so it idles smooth and doesn't rattle you teeth!!

Try Ken's suggestion about cleaning the Tach wire connections at the alternator. Hard to tell you which colored wires on your alternator?? (mine are the white and the brown wires)

A few thoughts

Breakin Away · July 20, 2023, 02:59:32 PM

Westerbeke's spec for maximum RPM of the M35B is 3000. You should achieve it underway in forward, or you may be over -propped.

AndyBC · July 20, 2023, 07:52:36 PM

My M35B can only get to 2800 rpm (tach reading) before the lever physically hits the binnacle guard. At 2300-2400, I'm going 7 knots in calm waters.

KWKloeber · July 20, 2023, 09:03:24 PM

Andy

I presume that there are no harness plugs -- so that the Tach signal is wired directly to the alternator?

pbyrne · July 21, 2023, 05:34:36 AM

Quote from: Ron Hill on July 20, 2023, 02:48:55 PM
pby : I believe that the tach range for your engine should be 0 to about 2800 rpm (maybe slightly more when not in gear!!) Idle should be about 1000 rpm so it idles smooth and doesn't rattle you teeth!!

Try Ken's suggestion about cleaning the Tach wire connections at the alternator. Hard to tell you which colored wires on your alternator?? (mine are the white and the brown wires)

A few thoughts

I'll do that! I found some photos that might help, but I don't see any wires in them, so maybe not very useful.

pbyrne · July 21, 2023, 05:36:52 AM

Quote from: KWKloeber on July 20, 2023, 02:01:07 PM
If the Tach is off before you trash it exercise the DIP switches or rotary switch setting. Contacts can become oxidized and produce false readings. There's troubleshooting for that in a manual for the gauges. If you don't find it on C34 Wiki I can probably find it elsewhere.

This it?

pbyrne · July 21, 2023, 05:54:07 AM

Quote from: AndyBC on July 20, 2023, 07:52:36 PM
My M35B can only get to 2800 rpm (tach reading) before the lever physically hits the binnacle guard. At 2300-2400, I'm going 7 knots in calm waters.

That's what I remember the boat doing last year. It's not quite doing either of those numbers, and that's why it feels like something is off. Other than the tach literally isn't reading more than 1800 full throttle...

KWKloeber · July 21, 2023, 01:24:41 PM

This sheet from Vee 3 speaks to contact oxidation.
I have other gauge troubleshooting guides from Vee 3 that I will upload when I have some time.

Ron Hill · July 21, 2023, 03:19:48 PM

pby : The picture needed is the REAR of the alternator where the tach wires attach.

Noting the alternator paint job - I find it nearly impossible to believe that the adjusting nut on the top bracket has paint that has never been broken!!!! Factory Paint???

A few thoughts

KWKloeber · July 21, 2023, 05:13:44 PM

Unless the PO had done any rewiring of the alternator, the factory schematic says that the tach signal is Brown #14. And unlike the earlier Universals, Westerbeke ran it thru the RV plug (no reply about whether the harness plugs were previously eliminated.)

To drive the Tach the Alt needs to send an alternating current signal -- something like 4-5 volts minimum.
Easy peasy to check at the "S" terminal on the Tach.

Craig Illman · July 22, 2023, 06:18:25 AM

An unrelated observation from your pictures. Your hoses are 23 years old. You should consider adding their replacement to your project list.

My 2 cents.....

pbyrne · July 22, 2023, 08:29:43 AM

Ok. Used the laser tach and the following was observed at the slip in neutral.

Idle:
Tach: 800
Actual: 1000

Full throttle to the stop:
Tach 2500
Actual: 3000

All linkage and stops looked correct and working as expected when moving through motion by my lovely wife and I watched it.

Checked racor and found no water and diesel looked clean to the eye. Have heard that marina is sensitive to fuel quality and there are no reported issues with fuel at marina.

The problem I have is that we didn't see 2500 on the tach but 1600, and the engine didn't sound like it has running full out.

Some local folks have said they have had issues with weeds at the head of the channel that require clearing when boat feels sluggish ...not sure if that was the issue?

All I can say is that at the slip in neutral the engine sounded good.