I'm thinking fuel filter...Update

[jcollins]

I'll try to describe this best I can. This is the first time since last year that I let the fuel get to a 1/4 tank. The bay was good today. 1' or less chop, no problem. We were coming into Middle River with the usual heavy boat traffic causing confused seas. In there the chop was 2+ from every direction. I went into Sue Creek where the limit is 6 knots. I was running about 1200 RPM. All of a sudden the RPM jumped up about 300. Sputtered a little. I pulled back on the throttle and it idled about 150-200 RPM higher than normal. Did not cut out. We just cruised around the creek for another 30 minutes or so. Storm clouds were coming in so we decided to go back to our marina and wait it out. Leaving Middle River, out to the bay and then back to our marina I ran 3200-3400 to get ahead of the storm. The boat ran fine. Back at the marina the idle was erratic. The storm came and went so we decided to go back out. Started, cut out. Re-started fine. Left the marina at 1700 RPM. Jumped up again to 2000. After that I ran my usual 2500-2700 RPM with no issues. This seems to be happening at 1700 RPM or less. I did not notice any smoke.

I'm thinking I stirred up some junk in the fuel tank?

[jleonard]

"Generally" a clogged filter will cause problems more at higher rpm than at lower rpm.
Surging rpm at lower rpm in my experience has been air getting into the fuel system.
Of course if the filter is badly clogged you could be drawing air into the fuel because of the high vacuum.
So yes, first change the filter and let us know what it looks like.

(I have friends who recently bought a house on Sue Creek...thanks for respecting their shoreline)

[jcollins]

Sue Creek is very nice. I have some friends that just bought a home there as well. I also kept my first boat there. 78 Sea Ray. Have friends at the yacht club and also get my fuel there. Nice anchorage.

[Denis]

I would agree that it sounds like it might be air in the line. Drain the site bowl on the primary filter and see if there is anything in it. I would also change both filters reguardless and fill up the tank. If it starts to build up a vaccuum it could suck in air but it also might be that your fuel guage is off a little and the fuel level is lower than it shows on the guage and with the bouncing around it could pick up air for a second or air bubbles in the fuel. Let us know what you find if anything. Denis

[jleonard]

TTT.
John..did you solve your problem?

[jcollins]

TTT.
John..did you solve your problem?

Before I could solve it, the problem went away. I filled the tank. Since then, it has started fine and idled fine.
I'm still going to change secondary fuel filters and check the primary.

[jleonard]

the problem went away. I filled the tank

Be careful here.....a split pickup tube in the tank can cause problems at lower tank levels (at or below the problem area) and then be fine at higher levels (above the problem). Sucking air will cause the engine to surge.
So take notice next time the tank is low and that might help diagnose.

[jcollins]

jleonard,
Thanks for that information. That makes the most sense so far. I will check it out during winter layup. For now I'll fill up at a 1/2 tank.

[jcollins]

Seems to be tank related. Level dropped to a 1/4 tank and the problem started again. I filled yesterday and once again it went away. So, I'm leaning towards your suggestions about the pickup tube in the tank. The obvious question is where I begin or do I leave this up to a mechanic?

I also noticed a sheen on the water in my slip when I shut down yesterday. This may or may not be related. It's also possible that it was already there since this is the first time I noticed it. Today I'll go back to the marina and let it idle for awhile to see what shows up.

[Denis]

John, I had to lift the hatch over the fuel tank last year to repair some wet balsa core. Use a utility knife to cut the caulk, remove the screws and just lift the hatch. It lifts easily and when off it exposes the top of the fuel tank. From there it should be an easy fix to remove the cover on top of the fuel tank. While the hatch is off you can change or check the fuel filler hose, vent, scuppers and anything else you can get to. You can also make sure your tank vent is supported properly to help during fill up. After you replace the fiberglass hatch, mix a batch of epoxy and pour it in all the screw holes and let it sit. After it's hard, use a pilot drill to start your screw hole, then chamfer to the same diameter as the screw head. Apply silicone caulk in the screw hole and set the screws, then apply a bead of caulk around the hatch as it was before. Let us know what you find in the tank, Im curious. Denis

[jleonard]

I also noticed a sheen on the water in my slip when I shut down yesterday.

Diesels do that.
I'm trying to recall if I ever saw one that didn't leave a sheen and I'm comming up empty.

Level dropped to a 1/4 tank and the problem started again

Sounds like a split or short pickup tube.
I replaced one a few years ago with a plastic one made by Tempo. Cost $10 and was recommended by my marina. End should be approx 1/4 to 1/2 inch off the bottom...cut on a 45 degree angle (eyeball).

[jcollins]

Thanks Everyone!

[RobS]

John, This is basically what you'll have with the rear deck removed, real straight forward once accessed.



The arrow points to the sender and the supply and return lines are next to it.

The epoxy in the screw holes suggestion by Denis sounds like a great idea. As far as re-sealing the perimeter of the deck, use Boatlife "Life Seal", not silicone, 5200, lifecalk, etc. Here's the link. I think I used 2 tubes, maybe a third, the large size that goes into a std caulking gun. It skins real quick so do short runs, maybe a foot at a time, and wipe with a wet rag to get a finished surface. It helps to have a partner for this. Here's the link for the product:

http://boatlife.ipower.com/shop/index.p ... ex&cPath=6

[jcollins]

Rob,
Thanks for the picture. It will help.
Time to fix up those fuel vent lines too.