MBL is a PIA

Ken Miller · Post by **Ken Miller** » Wed Jun 08, 2011 5:15 pm

I have a 1950 U-22 with MBL power. During restoration the engine was "remanufactured", totally gone through, but came back missing and not running correctly. It was subsequently broken down and the heads shaved and seemed to be fixed. Then we had more episodes where after a few minutes of use it would begin cutting out and missing, etc. We noticed that there was a short segment of rubber hose spliced into the fuel line and some debris/sediment in the fuel bowl, so we ran an all new 3/8" copper fuel line from the tank to the pump and cleaned out the fuel bowl. While it ran for nearly three hours without any problem this past weekend, as we exited a no-wake zone and went to accelerate she began missing and cutting out. This is the behavior she has exhibited all along through many attempts to correct. It always happens after either going through a no wake zone, idling for a short period of time, or turning the boat off for a short period of time (i.e. stop to talk to a friend in another boat). Then when I go to accelerate it does this. It was also exhausting blue smoke at the time, and only at the time, this was happening. Otherwise, it ran like a scalded cat. Can anyone advise where to further troubleshoot? Thanks.

Ken Miller

tom king · Post by **tom king** » Wed Jun 08, 2011 5:49 pm

what is the condition of your gas tank? could it be getting debris from the tank into the carb?

Ken Miller · Post by **Ken Miller** » Wed Jun 08, 2011 6:48 pm

During restoration the tank was removed, cleaned, lined and re-installed. I now realize I would have been better off with a new tank and wish I had done this. I have pulled the fuel bowl and found a small amount of very fine black sediment (finer than sugar):

Thanks for any replies.

Ken Miller.

mbigpops · Post by **mbigpops** » Wed Jun 08, 2011 7:50 pm

Maybe your idle is set too low and too much fuel goes in when you try to accelerate.

drrot · Post by **drrot** » Wed Jun 08, 2011 8:28 pm

Ken,
Try running it feeding from a small fuel can. Put a hose barb inthe fuel pump and put some fuel hose on it to the can. Have someone hold it while you go for a ride. Leave the engine box on shore.

Capn Taz · Post by **Capn Taz** » Thu Jun 09, 2011 5:27 am

It sounds like a vapor lock or fuel boiling situation. After sitting or idleing it would have time for the fuel to heat up in the lines as you are not using as much.

Check the route on the fuel lines. Did they get moved, are they to close to the engine where they might be getting excess heat?

Is the intake getting proper water flow? Check to see if it is getting hot. It could be boiling the fuel. That is why they have water lines cooling intakes on boats. Possibly one of the water jackets got plugged while putting the engine back together. To much sealant or a gasket shift can cause that. The line injecting water into the manifold could be corroded or plugged as well.

Just a few thoughts. I had an old dodge that loved to vapor lock on me, especially after idling for a long time.

Good luck, be sure to let us all know what you find!

Wood Commander · Post by **Wood Commander** » Thu Jun 09, 2011 7:04 am

I have found the water jacket going around the intake passage on M series intake manifolds can get totally clogged up and not let weater through. AND, the clog can remain moist enough to freeze in the winter and break out that section of the manifold. So there is a possibility that your intake charge is not getting cooled.

I spent many hours with a heated and bent piece of 1" flat bar with it's edge ground down to a sharp point, chiseling the hard, solidified sediment out of the passages (one of them on a replacement manifold) on my cruiser. It was extremely hard work, the rounded passage is extremely hard to work in.

After I had the passages cleaned out, I drilled and tapped drain holes in the manifolds for removable plugs so that they could be drained and cleaned out.

gbraker · Post by **gbraker** » Thu Jun 09, 2011 7:49 am

Brett;

What was the sediment made of?

Was it just mud. What would prevent that from happening?

Would you have to use heat exchangers?

Regards

Gary

tom king · Post by **tom king** » Thu Jun 09, 2011 8:56 am

sediment is a concern. the jets on a zenith carb are easy to block. I would recommend trying what Jim Staib suggested.

gbraker · Post by **gbraker** » Thu Jun 09, 2011 5:10 pm

Trying what Jim said would at least isolate the problem.
Right now we don't know.

Seems like it could be sediment in the bulb. You slow down and use less gas so it isn't flowing rapidly & the crap settles , then when more gas is called for the crap in the sediment bulb mixes with the increased flow and impedes the gas flow.

I had a car that acted that way years ago. It turned out to be a screen at the input to the carb that was being blocked when more fuel was called for. Cleaned the screen and problem gone.

Ken Miller · Post by **Ken Miller** » Thu Sep 22, 2011 12:13 pm

Capn Taz wrote:It sounds like a vapor lock or fuel boiling situation.

This past weekend I had a mechanic friend (used to be a Ford dealership service manager, has had Jeeps etc. with Herc engines) go out on the boat with me---he said the same thing, sounds like a vapor lock/fuel boiling situation or definitely a fuel failure issue.

First let me say what has most recently been done to the boat and any feedback would be greatly appreciated. The boat has a brand new Rayco fuel tank, brand new 3/8" copper fuel line (no rubber spliced in as was before I got the boat), new coil, new plugs. Re-manufactured MBL with Pertronix and 12v conversion. Running with 100% petroleum ethanol-free 93 octane fuel.

We idled out of the no-wake zone and went to accelerate (2400-2500 RPM) and the boat immediately began cutting out just like it always has. Mechanic observed the boat for several minutes (at 2400-2500 RPM--not even planed off) before adjusting anything. After 10-15 minutes, he touched the fuel line--it was not even hot. He began adjusting the carb setting, a little at a time and even back to where it was (my point here is he did not go hog wild and screw up the settings all at once). After 20-30 minutes he got to a point where he had both screws completely out and the boat was still having the same symptoms (2400-2500 RPM, cutting out--not planed off). He covered both holes with his fingers, and then uncovered them quickly, and then covered them again, and the boat didn't even show any signs of his manipulation. He also noticed that at the same time the engine cuts in and out air bubbles come into the fuel bowl. He was able to manually manipulate the butterfly to open all the way and the boat ran (redline) at 3100 RPM smooth as silk. His advice to me is to buy a new fuel pump and a new carburetor and start from scratch. Can anyone make any observations from this and offer any further advice? Thanks in advance for any responses.

Ken Miller

maritimeclassics · Post by **maritimeclassics** » Thu Sep 22, 2011 2:56 pm

I went through the same thing once, it turned out to be the fuel pump. The pump was not bad but was on the way out.

RRGadow · Post by **RRGadow** » Thu Sep 22, 2011 5:53 pm

maritimeclassics wrote:I went through the same thing once, it turned out to be the fuel pump. The pump was not bad but was on the way out.

Sounds like the fuel pump to me...they can do some wierd things when they are going thru the long slow death.

57 chris · Post by **57 chris** » Fri Sep 23, 2011 6:51 pm

All posts here are leaning toward fuel.. which might very well be the problem but if all else fails check your ignition system, points etc. These symptoms sound a lot like a problem I had that was a bad set of points!

Craig

Niqjh · Post by **Niqjh** » Fri Sep 23, 2011 7:34 pm

Have you tried with regular points, w/o the Pertonix? I had a similar experience years ago on an old Firebird car. Put points back in place of electronic ignition and all was well. The old ohc 6 would hit 7000 rpm easily. Was a head turner back in the day. sometimes the electronic ignitions have little issues. Easy to test anyway.

Good luck, keep us posted...

MBL is a PIA

MBL is a PIA

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