Return to the home page...

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

Reply
 
Thread Tools Display Modes
  #1   IP: 107.77.204.34
Old 06-24-2021, 09:57 AM
mwh2319 mwh2319 is offline
Senior Member
 
Join Date: Jul 2020
Posts: 16
Thanks: 6
Thanked 0 Times in 0 Posts
Unhappy HELP, Max 1200 RPM in forward, too slow

HELP, Max 1200 RPM in forward, too slow

My Atomic 4 starts rights up and in neutral will go up to 4000 RPM easily. But when I engage the transmission in forward it goes to a maximum of 1200 RPM.

I will admit the bottom of my boat, and probably my propeller too, are dirty. Which accounts for part of my boats slow speed of 1 MPH in forward. The hull speed is 6 MPH. Water temperature and oil pressure are fine.

But why will my Atomic 4 not get up to a recommended cruising RPM of 1800 RPM in forward gear?

Any thoughts would be appreciated.

Thanks,
mwh2319
Reply With Quote
  #2   IP: 207.32.171.10
Old 06-24-2021, 11:50 AM
capnward's Avatar
capnward capnward is offline
Afourian MVP
 
Join Date: Aug 2012
Location: Deer Harbor WA
Posts: 335
Thanks: 41
Thanked 147 Times in 107 Posts
If that was happening to me, I would take the carburetor apart and clean it, making sure no jets are clogged, including the small vents in the throat. At the same time I would replace the inline filter. You can drain the water separator to see if it is catching any water in the fuel. If you have a brown goo in the carb, that is caused by ethanol. Or maybe something is wrapped around your prop or shaft. a fuel pressure gauge would tell you if there is a fuel restriction before the carb. 1 mph is slow for 1200 rpm. When the bottom of my boat was incredibly fouled, I could still get 3 knots.
Reply With Quote
  #3   IP: 165.225.20.156
Old 06-24-2021, 11:55 AM
Surcouf's Avatar
Surcouf Surcouf is offline
Afourian MVP, Professor Emeritus
 
Join Date: May 2018
Posts: 361
Thanks: 328
Thanked 163 Times in 123 Posts
1 knot? that is reallllly slow.

Many different potential reasons...
- obvious one is of course a very dirty prop.... anyway you can anchor in clean water and remove barnacles?
- while in neutral at low speed, remove pulg wire one by one, to check that all cylinders are firing.
- after that it gets more complicated: fuel (pressure gage ok before carb? carb cleaned? no water in your fuel?), air (no problem on suction?), exhaust gases (unlikely, but is your exhaust pipe rubber? how old? Mine was crumbled inside, and "closed 75%", but still able to get 5 knots out of it), spark (spark plugs? spark plug wire test?), and compression (but to get only 1 knot, you would need at least 2 cylinders not running properly... A4 easily push most boats at 5 knots on 3 cylinders...)

The more educated Afourins will likely have more idea...
__________________
Surcouf
A nostalgic PO - Previously "Almost There" - Catalina 27 (1979)
Reply With Quote
The Following User Says Thank You to Surcouf For This Useful Post:
TimBSmith (06-24-2021)
  #4   IP: 72.69.36.126
Old 06-24-2021, 12:30 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
Invoking Occam's Razor, absolutely positively clean the hull and prop before removing a fastener from anywhere on the engine. Significant drag from a barnacled prop present exactly the symptoms you're describing.
Reply With Quote
The Following 2 Users Say Thank You to tenders For This Useful Post:
Easy Rider (06-24-2021), Sam (06-24-2021)
  #5   IP: 70.67.6.75
Old 06-24-2021, 07:42 PM
Easy Rider's Avatar
Easy Rider Easy Rider is offline
Afourian MVP
 
Join Date: Feb 2007
Location: British Columbia
Posts: 139
Thanks: 231
Thanked 30 Times in 20 Posts
I totally agree with Tenders. Do the basic stuff first. Make sure the prop and hull are clean - including the very bottom of the keel. Even a few barnacles on a prop will cause what you are describing.
__________________
Chuck

71 Ranger 29
Reply With Quote
  #6   IP: 32.211.28.40
Old 06-24-2021, 09:57 PM
Al Schober's Avatar
Al Schober Al Schober is offline
Afourian MVP
 
Join Date: Jul 2009
Location: Uncasville, CT
Posts: 2,002
Thanks: 16
Thanked 578 Times in 405 Posts
1 MPH??? While cleaning your prop, take a swipe at the knotmeter paddle. My knotmeter transmitter was removable from inside the hull - I just had to keep my bare foot over the hole while I cleaned it. Yes, it would grow barnacles too!
Reply With Quote
The Following 2 Users Say Thank You to Al Schober For This Useful Post:
Surcouf (06-25-2021), TimBSmith (06-24-2021)
  #7   IP: 47.38.39.58
Old 06-25-2021, 08:49 AM
Bayou Sailor's Avatar
Bayou Sailor Bayou Sailor is offline
Senior Member
 
Join Date: Sep 2020
Location: Mandeville, LA
Posts: 51
Thanks: 48
Thanked 18 Times in 9 Posts
I have had a similar issue. If your original prop was replaced with a larger or if it went from a 2 blade to a 3 blade it will reduce your max RPM somewhat. That combined with a dirty prop can cause extreme RPM loss.
Reply With Quote
  #8   IP: 107.77.203.38
Old 06-25-2021, 10:03 AM
mwh2319 mwh2319 is offline
Senior Member
 
Join Date: Jul 2020
Posts: 16
Thanks: 6
Thanked 0 Times in 0 Posts
Thanks everybody, very helpfull.
Reply With Quote
  #9   IP: 134.41.132.177
Old 06-25-2021, 03:22 PM
Mo's Avatar
Mo Mo is offline
Afourian MVP
 
Join Date: Jun 2007
Location: Halifax NS,
Posts: 4,470
Thanks: 292
Thanked 411 Times in 272 Posts
Last week I looked at a guys boat. He thought it wasn't running as good and not making the speed it did last year. First I looked at his firing order and checked his plugs for fire...all good there. Then looked at his distributer cap and the two hold down screws were rusty...not touched in years. We took it for a ride on the water and I got in the lazerette, loosened the 1/2 bolt on the dizy and rotated slightly... got her rpm back...knew then that he needed to get that cap off, replace it, and lubricate the centrifugal advance. With a little fooling around he sorted that out and it worked fine. I set the timing for him under-way a day later.

If the bottom is clean, prop is clean, engine seems to run fine in neutral generally I look for a sticking valve...Once you have cleared the prop and barnacles on the hull as culprits, in your particular case I'd check that the engine is handing out the power. Check compression, check fire, check timing...the small stuff. Then look at the weird stuff like a stuffing box too tight.
__________________
Mo

"Odyssey"
1976 C&C 30 MKI

The pessimist complains about the wind.
The optimist expects it to change.
The realist adjusts the sails.
...Sir William Arthur Ward.
Reply With Quote
The Following 2 Users Say Thank You to Mo For This Useful Post:
JOHN COOKSON (06-25-2021), Sam (06-25-2021)
Reply

Tags
rpm

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
reverse gear adjustments gilbert landin Reversing Gear 12 10-17-2013 08:31 PM
How much force is normal to put into gear? JimM Reversing Gear 19 07-24-2012 02:49 PM
Forward and Reverse Gear Adjustment Issues CraigRun Reversing Gear 12 05-17-2012 09:15 PM
Update - Engaging Forward Gear domagami Troubleshooting 1 05-27-2010 01:23 PM
Pressure on the drive lever to fully engage? Andy Mck Reversing Gear 6 10-08-2009 10:33 AM


All times are GMT -4. The time now is 05:23 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