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 Post subject: W50 surging RPMs
PostPosted: 27 Apr 2019 10:02 
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Skipper

Joined: 24 Sep 2013 09:20
Posts: 385
On a 7 hour motor sail passage, I started having regular RPM surges up from 1850 to 2000 without moving the throttle. It only would last about 2-3 seconds then back down. It was happening as often as a couple times a minute. It didn't seem to happen at all at low RPMs like 1200. I'm about 50 hours from last Racor filter change and haven't changed the on engine filter in a long time. Planning to change the filters. Am I on the right track here? I posted this question on a FB group, and in addition to changing the fuel filters, people have also mentioned an air leak could cause it. But, I don't even know where to start looking for that or how to fix. Next passage for us will be the Mona from Dominican Republic to Puerto Rico so need to make sure I have it running good. Anybody had this exact thing happen and know what it is and how to fix it? Thanks, Zach

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Zach Duncan
SV Holiday
Hull# 280


 
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 Post subject: Re: W50 surging RPMs
PostPosted: 27 Apr 2019 12:34 
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Skipper

Joined: 13 Feb 2011 21:19
Posts: 227
Location: Canyon Lake, TX
When my engine surges, it usually dies. Rant Sucks air and dirt from the bottom of the pickup tube.

If your engine isn't dying, it's a very small air leak. And it has to be between the tank and the first fuel pump. Obviously, as after that it would leak fuel. Can't help after that. Sorry.

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Wayne
Master and Commander of the Sailing Vessel Impetuous
Rider of Waleli Honda 1800 VTX
Subservient to no man except SWMBO
Any day without dock lines is a GOOD day!


 
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 Post subject: Re: W50 surging RPMs
PostPosted: 27 Apr 2019 16:28 
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Skipper

Joined: 24 Sep 2013 09:20
Posts: 385
Great info. I'll tighten all my hose clamps and check the fittings between the tank and the low pressure pump.

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Zach Duncan
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Hull# 280


 
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 Post subject: Re: W50 surging RPMs
PostPosted: 27 Apr 2019 16:43 
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Skipper

Joined: 16 May 2009 08:06
Posts: 173
A clog in the dip tube can cause air to leak in through the Racor.


 
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 Post subject: Re: W50 surging RPMs
PostPosted: 27 Apr 2019 18:23 
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Skipper

Joined: 14 Jul 2012 20:36
Posts: 411
Double check the Racor filter and the top seal. Break the compression fitting at the elbow on top of fuel tank, with 1/2 clear pvc hose pull a suction with your mouth. Should have very little restriction, if it does, blow into the elbow That means something is stopping flow. Pull the sending unit, get a hand pump with the clear pvc tubing, attached to a wood dowel and suck the bottom of the tank till clean.

Air leaks and HP fuel pump next to troubleshoot. The fuel pump, can act totally different after the engine has been run. The diesel fuel warms up, in the pump, the viscosity thins down and an older pump can't feed the demand.

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 Post subject: Re: W50 surging RPMs
PostPosted: 27 Apr 2019 23:25 
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Skipper

Joined: 29 Dec 2006 09:38
Posts: 579
Also could be that your tank vent is clogged. If you see bubbles in your racor—it might just be that spiders have sealed off the vent. I had that happen a couple times. Another way to test is to open the cap on the tank wen it is surging—if it stops, it is the vent. Also the pick up tubes on the old Tartans have a screen that clogs. Remove it. You do not need it and it causes more problems that it is worth. Tartan eventuallly stopped putting one in their tanks.
Ray Durkee


 
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