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'Miss Dot's" Gray Marine Model 70

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tuobanur
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'Miss Dot's" Gray Marine Model 70

Post by tuobanur » Sun Feb 28, 2016 2:24 pm

Hey guys and gals, been thrashing these past months trying to get Miss Dot ready for the Sunnyland show, had a mishap a few months back that did some serious hull damage but I have just about got that all fixed. The problem I'm having now is with the engine which also had a little something to do with my mishap. Trying to figure out if the problem is with the carburetor, having trouble getting it cranked and when I do it will only run at high RPM, as soon as I idle it down it shuts down and is even more difficult to restart. The carb is a Zenith 9255 up draft, have checked the tank for venting and all of that is good and is getting gas. Had to pull the carb off a while back to adjust the valves and while I had it off I changed a small gasket on the main needle valve because of a leak plus it would not lock the needle valve. Got that corrected and adjusted the valve to the recommended 2-1/4 turns out for the prestart with the final adjustment to be completed under load.
Any help with this matter would be greatly appreciated.
Terry
1941 Model 101 (16') Deluxe Runabout "Miss Dot"

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tuobanur
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Re: 'Miss Dot's" Gray Marine Model 70

Post by tuobanur » Sun Feb 28, 2016 2:30 pm

By-the-way, it hasn't always done this, this problem started the last time I had it out back in September.
PS. I only run non-ethanol.
Terry
1941 Model 101 (16') Deluxe Runabout "Miss Dot"

joanroy
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Re: 'Miss Dot's" Gray Marine Model 70

Post by joanroy » Mon Feb 29, 2016 6:38 am

I'd go with the process of elimination and work my way back to the carb. Start with a compression test and then check out everything related to spark/ignition. Could be weak spark problem. If everything else checks out OK then I'd take off the carb and go through it again. Did the problem start after the engine was worked on or did the stalling problem just come out of the blue?

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tuobanur
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Re: 'Miss Dot's" Gray Marine Model 70

Post by tuobanur » Mon Feb 29, 2016 9:18 am

Out of the blue, was running great.
Terry
1941 Model 101 (16') Deluxe Runabout "Miss Dot"

Howard Lehman
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Re: 'Miss Dot's" Gray Marine Model 70

Post by Howard Lehman » Mon Feb 29, 2016 9:46 am

Several years ago I had two boats, a 1954 Riviera and a 1941 Deluxe Runabout, each with the thee down draft carb KBL engine. I had the engine of the Riviera rebuilt, and the other boat's engine was to have been rebuilt and completely "gone through" by a very competent shop before I bought the boat, but that had occurred years before. I had both sets of the carbs rebuilt by a competent mechanic, one set ran well, the other didn't. The engine that ran poorly would only run at fast RPM, it couldn't idle, nor keep running at any other RPM. I suspected something else was wrong with the engine of that boat as the carbs had been rebuilt, so I switched carbs from one engine to the other. After firing up both engines, the other engine now ran poorly, so it was easy to lay blame onto one set of the carbs. Another check of the poorly running carbs showed nothing obvious. I inquired about a place that only rebuilt carburetors with an "ultra sound" process (I hope I'm not remembering the term/process incorrectly). In speaking with the owner of the shop about my problem, he said that the solutions available today to soak the carb parts in is not as strong a solution as it was in "the good old days", as those solutions were considered dangerous by EPA.......which I could understand. He said the new technique gets at the built up stuff in all of the little passageways, clearing everything out. Each carb would be thoroughly cleaned, and rebuilt correctly and set up so that all I would have to do was mount them on the intake manifold, and the engine would run like new. Hard to believe, but I told him to go ahead. Not long after this, the 3 carbs were done, I set them back on the engine, hooked everything up, and cranked the engine over. It started, ran at all RPMs, and didn't stall. When on the water, the engine ran great with no problems. Although I'm not entirely sure that I stated the term for the process used correctly (I said ultra sound), it worked great, and I have used that shop for other carbs and have always been happy with the results. I hope this is helpful. Good luck, Howard

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Re: 'Miss Dot's" Gray Marine Model 70

Post by joanroy » Mon Feb 29, 2016 1:52 pm

As suggested by Troy in another post, it's called ultrasonic carburetor cleaning.

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Re: 'Miss Dot's" Gray Marine Model 70

Post by jim g » Wed Mar 02, 2016 11:34 am

Idle circut is probably stopped up.

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tuobanur
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Re: 'Miss Dot's" Gray Marine Model 70

Post by tuobanur » Wed Mar 02, 2016 3:31 pm

Thanks to all, hope to figure it out this weekend, will keep you posted.
Terry
1941 Model 101 (16') Deluxe Runabout "Miss Dot"

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tuobanur
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Re: 'Miss Dot's" Gray Marine Model 70

Post by tuobanur » Mon Mar 07, 2016 10:26 am

Thought I would follow up on my fix. Most of the info I have been using for the initial start-up is from the original maintenance manual from Gray Marine, in the manual (for the carb.) it states that the main jet to be backed out 2-1/4 turns from the close position and the idling valve to be backed out 3/4 turns from the close position.
After checking the carb for air leaks and finding none I moved back to the adjustments, as it turned out for this particular application the main valve was backed out 2-1/2 turns and the idling valve required 1-1/4 turns. The idling valve was the main culprit for it not wanting to run at idle and the reason I say that is when I first tried with an additional 1/4 turn it was a little better and the more I added the better it got, I didn't go past the 1-1/4 turns. All is good now and the engine purrs at 500 RPM's.
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Terry
1941 Model 101 (16') Deluxe Runabout "Miss Dot"

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