Engine RPM gov. limit?
 

In an earlier post I mentioned that I had changed props and the engine was
only reaching about 2200 rpm.

My (new) MD2B manual indicates this engine should produce 25 hp at 2500 rpm.

Yesterday while running the engine in neutral at the dock I noted that the
governor is limiting the engine rpm to 2200 rpm.

I hesitate to tamper with the governor settings and the OEM seal wires are
still in place.

I wonder if I should investigate this situation or be satisfied with the
2200 rpm since my boat reaches hull speed at this rpm.

Any comments or suggestions would be appreciated.

Steve
s/v Good Intentions

Definitely don't mess with the governor without consulting a pro.

The engine should be able to reach "red line" in neutral, and it
shouldn't be hurt by pushing it right up to 2500 in neutral, as long
as its warmed up and has fresh oil, etc. If it will do this, there is
probably nothing wrong with it.

If it gets to hull speed at 2200, then that's all you're going to get
from it. Changing the prop might allow you to rev higher, but you're
already at over 85% of max, and that's what is often recommended for
small diesels, so my vote is for leaving it where it is.

I friend has just repowered with a Yanmar 3YM, and claims he was told
that he can run all day at 3600. I'm skeptical, however, and never
run my 3GM's at over 3200. I curious about other opinions on this.


Steve wrote:
In an earlier post I mentioned that I had changed props and the engine was
only reaching about 2200 rpm.

My (new) MD2B manual indicates this engine should produce 25 hp at 2500 rpm.

Yesterday while running the engine in neutral at the dock I noted that the
governor is limiting the engine rpm to 2200 rpm.

I hesitate to tamper with the governor settings and the OEM seal wires are
still in place.

I wonder if I should investigate this situation or be satisfied with the
2200 rpm since my boat reaches hull speed at this rpm.

Any comments or suggestions would be appreciated.

Steve
s/v Good Intentions

On Tue, 14 Jun 2005 08:15:56 -0700, "Steve" wrote:

In an earlier post I mentioned that I had changed props and the engine was
only reaching about 2200 rpm.

My (new) MD2B manual indicates this engine should produce 25 hp at 2500 rpm.

Yesterday while running the engine in neutral at the dock I noted that the
governor is limiting the engine rpm to 2200 rpm.

I hesitate to tamper with the governor settings and the OEM seal wires are
still in place.

I wonder if I should investigate this situation or be satisfied with the
2200 rpm since my boat reaches hull speed at this rpm.

Any comments or suggestions would be appreciated.

Steve
s/v Good Intentions


Since you are getting fairly close to the advertised top RPM, a good
question to ask might be "Is my tachometer reading correctly?"

Depending on your tachometer arrangement, there are several ways the
tach may be mis-reading. Mine senses the frequency of the AC produced
by the alternator, and probably (I haven't had reason to look, yet)
has a calibration adjustment, since the alternator speed vs engine
speed will depend on pulley diameters.

Talk to a mechanic to see if he has some independent means of
measuring engine RPM. I recall seeing a portable mechanical tach that
could be held against the end of the crankshaft.


--
Peter Bennett, VE7CEI
peterbb4 (at) interchange.ubc.ca
new newsgroup users info : http://vancouver-webpages.com/nnq
GPS and NMEA info: http://vancouver-webpages.com/peter
Vancouver Power Squadron: http://vancouver.powersquadron.ca

"Steve" wrote in news:H46dnTjcLcIoaTPfRVn-
:

I wonder if I should investigate this situation or be satisfied with the
2200 rpm since my boat reaches hull speed at this rpm.


Relax, Steve. It ain't gonna plane at 2500 RPM, either.....

Call ahead and tell 'em you're gonna be a week late. Throttle it back to
1200 RPM and enjoy the ride. You didn't really want to get back to the
dock, did you?

--
Larry

Why is everybody in a boat in such a hurry??
.....unless we're out of beer....

Peter Bennett wrote in
news.com:

Talk to a mechanic to see if he has some independent means of
measuring engine RPM. I recall seeing a portable mechanical tach that
could be held against the end of the crankshaft.



Strobotac. Mine's circa 1960. Turn the dial until the flashing xenon lamp
makes the shaft look like it's standing still, then simply read the dial.

Most tachs are way off...especially if the belt slips a little.
The same guy who calibrated the fuel guages calibrated the tachs, I think.

--
Larry

You know you've had a rough night when you wake up and your outlined in
chalk.

On my old Yanmar 1gm, I suspected the tach read low and eventually a
mechanic with a strobe verified this. The tach sensor is a little coil
mounted next to the flywheel that senses when each tooth goes by. I
suspect that either there were broken teeth (I never saw any) or maybe
corroded teeth, or maybe the tach meter was whacked.

wrote in
oups.com:

maybe the tach meter was whacked.

Analog frequency meter. The timing capacitor in them changes value and
they read wrong.

There IS an easy solution that is very accurate:
http://www.tinytach.com/tinytach/diesel.php
Even comes with a runtime hour meter that only times when the engine is
actually running...not when the switch is on.

--
Larry

You know you've had a rough night when you wake up and your outlined in
chalk.

I think it simply doesn't count running hours until it see RPM's on the
Tach. No RPM's (probably under a threshold of 100 RPM or so), no hours
counted.

"Dave" wrote in message
...
On Thu, 16 Jun 2005 01:20:22 -0400, Larry W4CSC said:

There IS an easy solution that is very accurate:
http://www.tinytach.com/tinytach/diesel.php
Even comes with a runtime hour meter that only times when the engine is
actually running...not when the switch is on.

Interesting item, Larry. Any idea how the transducer detects that an
injection has occurred?

--
Ken Heaton & Anne Tobin
Cape Breton Island, Canada
kenheaton AT ess wye dee DOT eastlink DOT ca

"Ken Heaton" wrote in
news:zSqse.76368$tt5.39986@edtnps90:

I think it simply doesn't count running hours until it see RPM's on the
Tach. No RPM's (probably under a threshold of 100 RPM or so), no hours
counted.


That's it. If it displays RPM, it runs the little clock.

We used TinyTachs on jetskis because of the crappy dream-o-meters jetski
companies put in them to make you feel wonderful....30-40% over reality.

I even saw one on a GoPed!...(c;

By the way, you don't have to provide it power. It will run a whole year
on a 9V alkaline battery.... That reduces the wiring to one wire and
ground....on the diesel. In a gas engine, there's no wiring at all! You
simply wrap the little wire coming out of it around any convenient spark
plug wire and it detects the pulses firing the plug by capacitive coupling
to the open-ended wire. You then select 2-stroke or 4-stroke to tell it
whether to count every pulse or every other pulse.

--
Larry

You know you've had a rough night when you wake up and your outlined in
chalk.

The Volvo MD (series) diesels all have a electrical pickup on the timing
gear housing. Not sure what type it is, only that it has two wires and they
go to the OEM tach.

Since these engines are intended to run without any dependance on a
electrical system (can be hand cranked) the tach circuit seem to be on it's
own as well.

Since the engine and OEM instrument are new I would suspect that the tach is
correctly matched to the engine.

Not much use talking to a Volvo dealer about this, since they don't deal
with these engines since production stopped 25 years ago.. Anytime I mention
this model to a dealer they 'recoil' and start bad mouthing it as 'old
technology' and try to sell me one of their "Turbo Charged Tractor" engines.

Me? I love them! This being my second of this model. I have accumulated
enough spare parts to keep it running for the next 25-30 years.

Steve
s/v Good Intentions