Cruisers Forum

Join CruisersForum Today

Thread Tools Rate Thread Display Modes
Old 15-06-2015, 15:12   #1
Registered User

Join Date: Sep 2012
Posts: 16
3GM30F Power loss

Background 1997 Beneteau 321
Just got back from a sail ,on return to moring we were powering into a 25 MPH head wind and falling tide (strong current)
After aprox 45 minutes RPM droped to 1800 for a few seconds then returned to cruse RPM 2500 (engine smoothe)repeated this sequence 2500 down to 2000 RPMs another 4 times
before we were back on mooring,engine runs smoothe in and out of gear ,
Took a few minutes and checked vent line to fuel tank OK
Day 2--Motor cold on mooring engine started on first roll of starter,ran engine ran normally (no load) took RPMs up to 2500 no issues
Took boat off mooring after about ten minutes RPMs droped from 2500 to
1800 then back to 2500 and kept cycling like this , returned to mooring engine stalled during pick up of mooring ,restared without any problem
Any suggestions? Thanks in advance

David Clark is offline   Reply With Quote
Old 15-06-2015, 15:24   #2
Senior Cruiser
colemj's Avatar

Cruisers Forum Supporter

Join Date: Oct 2005
Location: Presently on US East Coast
Boat: Manta 40 "Reach"
Posts: 10,043
Images: 12
Re: 3GM30F Power loss

Dirty fuel filter(s)? Air leak?



You do not need a parachute to skydive. You only need a parachute to skydive twice.
colemj is offline   Reply With Quote
Old 16-06-2015, 06:11   #3
Registered User

Join Date: Dec 2010
Location: W Carib
Boat: Wildcat 35, Hobie 33
Posts: 6,060
Re: 3GM30F Power loss

Sounds like classic dirty fuel filter behavior. I would suspect this first.

Could be a vaccum leak, but not likely unless you've worked on some part of the fuel system recently.

Could be an intermittently clogged vent. This has happened to me on a few monos in very rough weather. Their vent hoses had a dip in them that would fill with fuel when heeled hard in rough weather...then drain when the boat stood up straight.

Could be the pick up tube sucking air...particularly on monos with irregularly shaped tanks in rough conditions with lots of heel.

But, I would bet its just a clogged fuel filter.
belizesailor is online now   Reply With Quote
Old 16-06-2015, 06:17   #4
Registered User

Join Date: Dec 2010
Location: W Carib
Boat: Wildcat 35, Hobie 33
Posts: 6,060
Re: 3GM30F Power loss

Filters always clog at the worst moment. A minor enhancement that can save your butt in these circumstances is to install a pump or bulb upstream of the filter. Then you can apply some positive assist pressure upstream of the filter to keep the engine running those last few feet. Also handy for maintenance use, like priming the system after fuel filter changes.

A vacuum gauge is also handy so you can see the problem developing.
belizesailor is online now   Reply With Quote
Old 16-06-2015, 06:46   #5
Senior Cruiser
Roy M's Avatar

Cruisers Forum Supporter

Join Date: Feb 2007
Location: Southwestern Yacht Club, San Diego, CA
Boat: Searunner 40 trimaran, WILDERNESS
Posts: 2,925
Images: 4
Re: 3GM30F Power loss

Parallel fuel filters, with the vacuum gauge. Mine,also, has a Racor vacuum switch in line with the vacuum gauge. When the vacuum reaches 3 (the yellow zone), it sets off a buzzer and an LED light above the vacuum gauge. Then I pop down and flip the A-B fuel switch to a fresh filter. You then have plenty of time to change the filter. I learned this from making deliveries where the tanks got stirred up and we had picked up crappy fuel. It gives me a great deal of confidence entering a difficult harbor channel in bad weather.
Roy M is offline   Reply With Quote

3gm, 3gm30

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

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
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
Power Loss in Tohatsu 5HP Outboard ssullivan Engines and Propulsion Systems 64 30-11-2015 13:17
3GM30F Intermittent power loss ScuzzMonkey Engines and Propulsion Systems 10 15-08-2013 18:12
Loss of Power - Inboard Volvo Penta Diesel Engine Kiwi@Sea Engines and Propulsion Systems 6 24-11-2011 08:24
Loss of Power StClair Sailor Engines and Propulsion Systems 5 30-04-2010 09:50
Yanmar 30GM30F - Black Smoke, Power Loss FlatHatter Engines and Propulsion Systems 4 15-09-2009 20:03

Our Communities

Our communities encompass many different hobbies and interests, but each one is built on friendly, intelligent membership.

» More about our Communities

Automotive Communities

Our Automotive communities encompass many different makes and models. From U.S. domestics to European Saloons.

» More about our Automotive Communities

Marine Communities

Our Marine websites focus on Cruising and Sailing Vessels, including forums and the largest cruising Wiki project on the web today.

» More about our Marine Communities

Copyright 2002-2015 Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 20:32.

Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2016, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2016, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.