3GM 30F power loss

[Beneteau 321]

Background 1997 Beneteau 321
3GM30F
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 will trouble shoot further tomorrow
Any suggestions? Thanks in advance

 

[Jim Seamans]

I had this same problem on my H356 with the 3GM30F, but was only dropping 50-100 rpm. I still don't know what was causing it. I came out of the water two weeks ago and back in today. While out, I pulled the exhaust elbow and cleaned it out. Not real bad but what the heck.. Installed new gasket and exhaust hose to muffler. Will be out starting June 21 for about 8 days and will keep an eye on it... real strange

 

[Allan12210]

Check that there isn't a screen crammed up in the fuel pick up tube. You have to extract the tube from the fuel tank and look up inside it. If so, pop it out with an ice pick or some such implement. You have plenty of filtration before the lift pump.

 

[Claude L.-Auger]

Allan may be on to something. 25 MPH headwind, heavy current generally means unsteady boat, i.e. rock & rolling motion. If tank is low and there are some dirty stuff floating around, it will plug up the pick up tube momentarily and thus starve the engine for a few seconds...until the next wave cleans it up...on and off. Once boat is stable at the dock, it should run normally. good luck with the diagnostic.

 

[Beneteau 321]

Up date on loss of power;
Replaced primary and secondary filters,bleed system ,engine started and ran smooth left mooring and when at 2500 RPM same problem resurfaced ,cracked bleeder on HP pump
Air! tried a few more times still getting air
Back on mooring started to trouble shoot suction side of system,eventually found a loose possible broke suction line fitting on top of fuel tank. Unable to get clear access to top of tank,setting up now to cut an access panel to get at top of tank (inside aft cabin)

 

[Beneteau 321]

UP date did confirm the Plastic elbow on the fuel pick up tube was cracked and sucking air ,removed pick up tube and started to source a replacement-area Beneteau dealer never responded to my E Mail either did Beneteau USA
Found a replacement pick up tube (Mermaid Marine on Prine Edward Is) that screwed into top of tank -perfect fit
Suggest other Beneteau ornery inspect this fitting for defects

 

[JCDuffy56]

Hi, did you get around to the fuel tank access port installation? for me, I had bad fuel; had fuel polishing, new filters installed, removed, inspected and clean injectors in July. Now having same problem -- above 2000, white smoke and engine rattle, then next day, engine stalled, restarted running rough and stalled. So, considering access plate to fuel tank to get a much better cleaning done.

thanks,

 

[Beneteau 321]

Cut an access opening about 4" by 6" near top of tank ,drilled small pilot hole first to get position (caution too low and you will drill into tank not a good idea) then marked out the rectangle,drilled a series holes used a dry wall saw to cut out .Cut a piece of 1/4" plywood two coats af cherry stain/Minwax coat of varnish two small mounting screws job complete.Plan to replace Vent line fitting on tank when we lift the boat for the season. (will try to get some pics of install