Return to the home page...

Go Back   Moyer Marine Atomic 4 Community - Home of the Afourians > Discussion Topics > General Interest

Reply
 
Thread Tools Display Modes
  #1   IP: 69.156.124.149
Old 10-15-2008, 10:08 PM
Dave O Dave O is offline
Senior Member
 
Join Date: Nov 2007
Location: Port Credit, ON
Posts: 74
Thanks: 0
Thanked 1 Time in 1 Post
Uneven RPM

Late this season I noticed that I am getting uneven RPM when in neutral at the dock.

After the engine warms up and still in neutral, engine speed periodically increases or decreases apparently "at will". The symptoms are exactly as if someone was adjusting the throttle up and down. The engine does not die ... it runs smoothly without hesitation. No roughness. Just as if an invisible hand was moving the throttle lever up and down somewhat. It is periodic.

I had the same problem last year. During the winter I did a complete tune up including adding a new carb. The problem seemed to be solved, but it has reappeared during the last 2-3 weeks or so.

I do not notice this when the boat is underway ... but that may simply be because engine speed it typically higher and I can not evaluate RPM as easily.

Today I took a look at the throttle connection at the carb and did not see any movement that might explain the situation.

I do not have a tach.

Does anyone have any suggestions?

Thank you

Dave
C&C29Mark I
Port Credit, ON
Reply With Quote
  #2   IP: 38.118.55.136
Old 10-16-2008, 11:39 AM
Don Moyer's Avatar
Don Moyer Don Moyer is offline
 
Join Date: Oct 2004
Posts: 2,811
Thanks: 0
Thanked 183 Times in 124 Posts
Dave,

Assuming the problem occurs mostly at idle, this scenario is usually caused by the idle RPM being set by the end of the cable travel and not by the set screw on the carburetor throttle arm. You can check this by looking closely at the end of the idle set screw to be sure it seats firmly against the stop pin.

Don
Reply With Quote
  #3   IP: 64.231.200.110
Old 10-17-2008, 11:16 PM
Dave O Dave O is offline
Senior Member
 
Join Date: Nov 2007
Location: Port Credit, ON
Posts: 74
Thanks: 0
Thanked 1 Time in 1 Post
Thank you Don. I took the boat out for another run today and unfortunately the problem has worsened.

At idle in neutral at the dock I am getting the uneven RPM described earlier. I checked the idle screw and it seems to be positioned "OK".

However, now underway, I am experiencing the same thing and this is the first time I have experienced that.

I don't have a tach but:

1. Engine is fully warmed up
2. Running at about 2.5 - 3 knots consistent no wind
3. No change on my part to the throttle.
4 Am experiencing the same "up and down" engine speed I described earlier. Seemingly at will RPM will decrease, then increase (back to the original setting) and then decrease and increase with no change in the throttle position. It as become a bit of a cycle. During all this the engine is smooth.

Can anyone suggest further things to look at? The carb is new in the spring and I imagine that any blockage or dirt would cause roughness? Any restriction in the fuel supply would do the same?

Is this most likely a linkage issue? Or perhaps the mech. fuel pump is starting to fail and is thus delivering inconsistent fuel flow?

Thank you

Dave
C&C 29 Mark I
Port Credit, ON.
Reply With Quote
  #4   IP: 38.118.55.136
Old 10-20-2008, 08:02 AM
Don Moyer's Avatar
Don Moyer Don Moyer is offline
 
Join Date: Oct 2004
Posts: 2,811
Thanks: 0
Thanked 183 Times in 124 Posts
Dave,

These RPM excursion episodes are the most difficult to diagnose of any
problem I can think of - thankfully, they don't happen very often.

If the throttle cable is not the problem (you could station someone at the
engine to actually observe the throttle arm on the carburetor to see if it
is moving), here are a couple other suggestions:

1) Vacuum leak. Vacuum leaks will sometimes come and go in tubing joints
as with a loose fitting on a scavenge tube, a defective PCV valve on an
Indigo Electronics crankcase venting kit, etc.

2) Also in the category of a long shot, a small flat piece of scale just
ahead of the main jet could sequentially block fuel as it is moving from the
main passage through the main jet. If you have access to the carburetor you
can remove the main passage plug and drain the main passage into a clean
glass jar (this is the lowest point in the carburetor) to check for dirt in
the fuel. While the plug is removed, it's also a good idea to flush a bit
of fuel through the carburetor by operating the fuel pump a few seconds.

3) Also, as a generic suggestion, always think back to the time a problem
began and try to figure out if anything else changed in the engine's life;
like some kind of maintenance action.

Don

Last edited by Administrator; 10-19-2017 at 07:05 AM.
Reply With Quote
  #5   IP: 165.89.84.89
Old 10-18-2017, 03:54 PM
tmcdonagh tmcdonagh is offline
Senior Member
 
Join Date: Oct 2017
Location: Buzzards Bay
Posts: 18
Thanks: 14
Thanked 1 Time in 1 Post
RPM excusions

I am experiencing this same problem. Any new insight on the problem?

Thanks, Tom

Any
Quote:
Originally Posted by Don Moyer View Post
Dave,

These RPM excursion episodes are the most difficult to diagnose of any
problem I can think of - thankfully, they don't happen very often.

If the throttle cable is not the problem (you could station someone at the
engine to actually observe the throttle arm on the carburetor to see if it
is moving), here are a couple other suggestions:

1) Vacuum leak. Vacuum leaks will sometimes come and go in tubing joints
as with a lose fitting on a scavenge tube, a defective PCV valve on an
Indigo Electronics crankcase venting kit, etc.

2) Also in the category of a long shot, a small flat piece of scale just
ahead of the main jet could sequentially block fuel as it is moving from the
main passage through the main jet. If you have access to the carburetor you
can remove the main passage plug and drain the main passage into a clean
glass jar (this is the lowest point in the carburetor) to check for dirt in
the fuel. While the plug is removed, it's also a good idea to flush a bit
of fuel through the carburetor by operating the fuel pump a few seconds.

3) Also, as a generic suggestion, always think back to the time a problem
began and try to figure out if anything else changed in the engine's life;
like some kind of maintenance action.

Don
Reply With Quote
  #6   IP: 64.134.69.61
Old 10-19-2017, 01:12 PM
tenders tenders is offline
Afourian MVP
 
Join Date: May 2007
Location: Harlem YC, City Island, NY
Posts: 1,439
Thanks: 46
Thanked 259 Times in 170 Posts
I’ve had mild symptoms that might fall into this category that were caused by occasional sticking valves. The solution was to put a few shots of Marvel Mystery Oil into the fuel, in the dosage recommended on the bottle (1 ounce every 10 gallons, I think, but don’t quote me on that).

I do this for all the fuel that goes into the boat’s tank, and the valves do not stick any more.
Reply With Quote
The Following User Says Thank You to tenders For This Useful Post:
tmcdonagh (05-29-2018)
  #7   IP: 162.233.58.75
Old 10-19-2017, 07:40 PM
pknier's Avatar
pknier pknier is offline
Senior Member
 
Join Date: Oct 2004
Location: Manitowoc, WI
Posts: 44
Thanks: 3
Thanked 1 Time in 1 Post
Do not count out a developing "water in the fuel" problem...from my experience with our motor...at high speed it would change slightly in RPMs and sound slightly different...Did not make much of it until it stopped idling at low RPM and then hard starting. During the troubleshooting process, found water in the sediment bowl and then in the separating filter...cleaned and replaced and we are fine...back to excellent low RPM idle - no variation in the high-speed RPMs and no variation in sound
Reply With Quote
The Following User Says Thank You to pknier For This Useful Post:
tmcdonagh (05-29-2018)
  #8   IP: 71.179.128.129
Old 10-19-2017, 08:03 PM
sdemore sdemore is offline
Senior Member
 
Join Date: Nov 2016
Location: Pasadena, MD
Posts: 230
Thanks: 84
Thanked 43 Times in 33 Posts
Two cents on my recent experience. I was seeing a similar thing, more in cruise than at idle and more the harder I pushed it. Turned out that the reversing gear needed to be adjusted. It was never really hitting a good neutral position and the clutch was slipping intermittently. Readjusting the reversing took care of it on mine.
__________________
Steve Demore
S/V Doin' It Right
Pasadena, MD
Reply With Quote
The Following 2 Users Say Thank You to sdemore For This Useful Post:
Administrator (10-20-2017), tmcdonagh (05-29-2018)
  #9   IP: 165.89.84.89
Old 09-04-2018, 10:05 AM
tmcdonagh tmcdonagh is offline
Senior Member
 
Join Date: Oct 2017
Location: Buzzards Bay
Posts: 18
Thanks: 14
Thanked 1 Time in 1 Post
RPM excusions

I routinely experience RPM excusions. This weekend I noted the amperage meter reflected the RPM excursion. When the RPM dropped, the AMP meeter went high, when it returned to "normal", the AMP meter needle returned to the zero position. My chartplotter (B&G) can display voltage and I noted high voltage (15.2-15.8) when RPM dropped and 13.2 volts when RMP dropped. I have always had poor battery charging with my boat. I am on the 2nd house battery after 5 years. Perhaps my Alternater and/or voltage regulator is bad? The alternator appears to be stock/original and there are no markings or model numbers that I can see. Any suggestions?
Reply With Quote
  #10   IP: 141.239.218.236
Old 09-04-2018, 12:54 PM
roadnsky's Avatar
roadnsky roadnsky is offline
Afourian MVP
 
Join Date: Dec 2008
Location: Lake Mead, NV
Posts: 3,104
Thanks: 24
Thanked 467 Times in 309 Posts
Quote:
Originally Posted by tmcdonagh View Post
When the RPM dropped, the AMP meeter went high, when it returned to "normal", the AMP meter needle returned to the zero position. My chartplotter (B&G) can display voltage and I noted high voltage (15.2-15.8) when RPM dropped and 13.2 volts when RMP dropped. I have always had poor battery charging with my boat. I am on the 2nd house battery after 5 years.
•How long do these episodes last?
•What kind of batteries?

15+ volts is a likely reason for your toasted batteries.

Quote:
Perhaps my Alternater and/or voltage regulator is bad?
Very likely.
Our resident DC experts will be along soon and can suggest some testing for you to perform.
__________________
-Jerry

'Lone Ranger'

1978 RANGER 30
Reply With Quote
The Following User Says Thank You to roadnsky For This Useful Post:
tmcdonagh (09-04-2018)
  #11   IP: 165.89.84.89
Old 09-04-2018, 02:58 PM
tmcdonagh tmcdonagh is offline
Senior Member
 
Join Date: Oct 2017
Location: Buzzards Bay
Posts: 18
Thanks: 14
Thanked 1 Time in 1 Post
Thanks for the reply Roadnsky.

High voltage periodicity is anywhere from 10 to 60 seconds followed by random 10-60 low voltage. I have standard flooded Lead acid batteries installed.


Quote:
Originally Posted by roadnsky View Post
•How long do these episodes last?
•What kind of batteries?

15+ volts is a likely reason for your toasted batteries.


Very likely.
Our resident DC experts will be along soon and can suggest some testing for you to perform.
Pics of the unlabelled alterator attached.

Thanks,

Tom
Attached Images
  
__________________
S/V SERVUS
Tartan 30
Hull number 513
Reply With Quote
  #12   IP: 141.239.218.236
Old 09-04-2018, 03:37 PM
roadnsky's Avatar
roadnsky roadnsky is offline
Afourian MVP
 
Join Date: Dec 2008
Location: Lake Mead, NV
Posts: 3,104
Thanks: 24
Thanked 467 Times in 309 Posts
That's an original stock MOTOROLA 35A alternator.
I think, given the short durations, that you have a regulator issue.
I can give you a few suggestions...

BUT, let's wait for the guys who know more about this to help us along.

Paging Dr's Neil and Joe...


EDIT - Could you post a pic showing the area of that alt where the wiring is connected please.
The opposite side of where the pulley is. Also we're looking for a tombstone looking casing
__________________
-Jerry

'Lone Ranger'

1978 RANGER 30

Last edited by roadnsky; 09-04-2018 at 03:41 PM.
Reply With Quote
The Following User Says Thank You to roadnsky For This Useful Post:
tmcdonagh (09-05-2018)
  #13   IP: 24.152.132.140
Old 09-04-2018, 05:38 PM
ndutton's Avatar
ndutton ndutton is offline
Afourian MVP
 
Join Date: May 2009
Location: Torrance, CA
Posts: 9,619
Thanks: 198
Thanked 2,208 Times in 1,425 Posts
Quote:
Originally Posted by roadnsky View Post
BUT, let's wait for the guys who know more about this to help us along.
Paging Dr's Neil and Joe...
Nah, you don't need me. Roadnsky is all over this. The regulator is done, 15+ volts is murder on your batteries and heaven forbid you have electronic ignition. Instead of replacing the regulator on an old, low capacity alternator it might be an excellent time to improve your charging system. If you agree, be sure the new alternator is ignition proof.
__________________
Neil
1977 Catalina 30
San Pedro, California
prior boats 1987 Westsail 32, 1970 Catalina 22
Had my hands in a few others
Reply With Quote
  #14   IP: 71.178.80.35
Old 09-04-2018, 10:37 PM
sastanley's Avatar
sastanley sastanley is offline
Afourian MVP
 
Join Date: Sep 2008
Location: Solomons, MD
Posts: 7,016
Thanks: 1,134
Thanked 600 Times in 442 Posts
Quote:
Originally Posted by ndutton View Post
Nah, you don't need me. Roadnsky is all over this. The regulator is done, 15+ volts is murder on your batteries and heaven forbid you have electronic ignition. Instead of replacing the regulator on an old, low capacity alternator it might be an excellent time to improve your charging system. If you agree, be sure the new alternator is ignition proof.
+1 what Neil & Jerry said. If you have had issues in the past, now is the time to come up with 2.5 good-old-boat bucks ($250). (New boats a boat buck is $1000)!

Jerry, that sideways pic is good enough to tell me with 95% certainty that is an OEM regulator attached to the outside. I am not sure how it has survived this long and still be serviceable at all!!

Common options are replacement of the entire thing with a proven unit like what Moyer sells (55A), or if you are intent on keeping the 35A Motorola, take it to a local shop for a rebuild..they will test the alt. and then can probably get you a regulator, which I agree is most likely suspect. The stock regulator that bolts on the outside of the alternator is 13.8V output..adequate for its time, but a little low by today's standards of 14.2-14.4v for lead acid batteries, along with the low by today's standards 35A output. I suspect that cost to be over $100, but probably less than $200 for a rebuild.
Below is a link to Moyer's offerings, which is my recommendation also. The 55A is about $230 and should solve all of your problems, unless you have extreme battery loads (I do find it very interesting you have B&G instruments on your T-30!! ). I would heartily consider new over rebuilding the old one..but that is your call. Taking yours to a rebuild shop for an estimate may help you decide. If you don't have a reliable shop around and want to try to fix the existing, we can discuss further about finding some regulators on the internet for your 35A, but then we are in experimental land.

https://moyermarine.com/product-category/electrical/
__________________
-Shawn
"Holiday" - '89 Alura 35 #109
"Twice Around" - '77 C-30, #511 with original A-4 & MMI manifold - SOLD! (no longer a two boat owner!!)
http://www.moyermarine.com/forums/signaturepics/sigpic3231_6.gif

Last edited by sastanley; 09-04-2018 at 10:55 PM.
Reply With Quote
The Following User Says Thank You to sastanley For This Useful Post:
tmcdonagh (09-05-2018)
  #15   IP: 70.186.110.20
Old 09-04-2018, 11:09 PM
CajunSpike's Avatar
CajunSpike CajunSpike is offline
Senior Member
 
Join Date: Jan 2018
Location: New Orleans, LA
Posts: 240
Thanks: 222
Thanked 41 Times in 31 Posts
Hoping this is useful...

i used to have a shrimp boat with a diesel engine.
I found and installed a NAPA single connection alternator to power all the electrical winches and accessories.
https://www.napaonline.com/en/p/RPS7152PS

Besides the mount, there was only 1 wire connection required, the hot to the battery.

Would this be appropriate(assuming the mounting works) to put on an A4?
__________________
Bill L.
1972 Ericson 27
Hull #61
Atomic 4
Reply With Quote
  #16   IP: 24.152.132.140
Old 09-04-2018, 11:45 PM
ndutton's Avatar
ndutton ndutton is offline
Afourian MVP
 
Join Date: May 2009
Location: Torrance, CA
Posts: 9,619
Thanks: 198
Thanked 2,208 Times in 1,425 Posts
Quote:
Originally Posted by CajunSpike View Post
Would this be appropriate(assuming the mounting works) to put on an A4?
Sure. I've had one for years and it has performed well. I'll confess however I've had three modifications done to it:
  1. AC tap for an alternator driven tachometer added
  2. 14.7V internal regulator replaced with a 14.0V (might be a 14.2V, can't remember for sure right now)
  3. Excite wire added
The excite wire wasn't my idea, it was done by the shop when they replaced the regulator. It gets the alternator producing immediately rather than having to rev to 1000 RPM to wake it up. The first time I connected it to the coil + terminal and it performed exactly as expected, sort of. Sure enough it was charging at the launch but the single wire circuitry backfed 12V + to the excite wire so when I switched off the ignition the engine kept running. Not cool. The solution was to connect the excite wire to the starter solenoid R post, energized during starting but disconnected after startup. Way cool.

The picture is pre-modification
Attached Images
 
__________________
Neil
1977 Catalina 30
San Pedro, California
prior boats 1987 Westsail 32, 1970 Catalina 22
Had my hands in a few others
Reply With Quote
The Following User Says Thank You to ndutton For This Useful Post:
CajunSpike (09-05-2018)
  #17   IP: 70.186.110.20
Old 09-05-2018, 01:31 AM
CajunSpike's Avatar
CajunSpike CajunSpike is offline
Senior Member
 
Join Date: Jan 2018
Location: New Orleans, LA
Posts: 240
Thanks: 222
Thanked 41 Times in 31 Posts
So the unmodified install looked like it was plug and play then.


Good to know in a pinch.
__________________
Bill L.
1972 Ericson 27
Hull #61
Atomic 4
Reply With Quote
  #18   IP: 24.152.132.140
Old 09-05-2018, 04:05 AM
ndutton's Avatar
ndutton ndutton is offline
Afourian MVP
 
Join Date: May 2009
Location: Torrance, CA
Posts: 9,619
Thanks: 198
Thanked 2,208 Times in 1,425 Posts
Quote:
Originally Posted by CajunSpike View Post
So the unmodified install looked like it was plug and play then.
Almost. I neglected to mention a minor modification to the lifting eye bracket made with a grinder to allow sufficient swing.
Attached Images
 
__________________
Neil
1977 Catalina 30
San Pedro, California
prior boats 1987 Westsail 32, 1970 Catalina 22
Had my hands in a few others
Reply With Quote
The Following User Says Thank You to ndutton For This Useful Post:
CajunSpike (09-05-2018)
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
uneven sooting of plugs Figment Troubleshooting 1 07-24-2006 09:48 AM


All times are GMT -4. The time now is 01:41 PM.


Powered by vBulletin® Version 3.8.9
Copyright ©2000 - 2024, vBulletin Solutions, Inc.


Universal® is a registered trademark of Westerbeke Corporation

Copyright © 2004-2024 Moyer Marine Inc.

All Rights Reserved