85 hp fuel pumps, carb questions.

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85 hp fuel pumps, carb questions.

Postby amuller » Thu Aug 10, 2017 7:51 pm

My V4 project is almost ready for the river. Controls working but really wants a new throttle cable.

Fuel pump is 433390. This pump and similar seems to fit a whole lot of OMC motors. They only cost $20 or so from various online sources. This one seems to work OK, but am wondering: Are repair kits available for these if needed? Maybe not worth bothering with for the cost of a new pump?

Do people here think the ty-raps for hose clamps are OK? OMC seems remarkably casual about fuel lines compared to Merc with it's fancy threaded fittings.

Carbs: Hated to do it, but knowing what will happen to a cylinder if a carb bore goes lean, I took them off. Glad I did because the bowl gaskets are sort of dissolving and shedding bits. I don't see any other carb issues.

I only really need the bowl gaskets but might as well replace the flange gaskets. The material I found obviously did not hold up. (Actually, one black one didn't, one tan one did better but is still slightly swollen.)

Anything else I should pay attention to on these carbs? I ordered two Sierra 18-7046 kits.

Breather pad in pan under carbs seems fouled enough to limit air intake.

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Location: Rhode Island

Re: 85 hp fuel pumps, carb questions.

Postby fleetwin » Sat Aug 12, 2017 10:21 am

OK, first, I would not mess with the fuel pump if it is working OK....Perhaps just order a repair kit and keep it onhand, that will ensure the pump never quits....
Next, the issue is not really using tie wraps, but reusing old fuel lines that have hardened and stretched. Clamping down on old fuel lines with metal worm clamps will not solve a sealing issue, they will just weaken the fuel lines further and break flimsy plastic fittings. So, my answer is that good tie wraps (not cheesy stuff that will melt/stretch) will secure/seal decent fuel lines just fine, don't waste time and money using worm clamps. The fuel pump only develops about 3-4PSI fuel pressure. Replace worn fuel lines, and don't try to substitute molded fuel lines (ones with preformed bends) with conventional straight hose, the bends you add might end up kinking.
The important thing to check/clean in those carbs are the high speed fixed jets. Did you remove them? Don't try removing them if you don't have the correct jet screw driver, you will bung up the threads and create loose debris in the bowl. The jets might look clean when looking through the straight passage in the bowls, but they tend to develop a fine coating of crud on their passage walls which is not visible to our eyes. This is enough to cut down the opening a few thousandths of an inch, which is enough to create a lean condition at high speeds and resulting powerhead damage.
Passing a pipe cleaner soaked in carb cleaner through the jets while still installed is a pretty great way to clean them thoroughly, you will see the color change on the pipe cleaners which is from the fine coating of crud on the jet walls. Again, please be careful not to create debris by leaving pipe cleaner fur in the bowls. Needless to say, the carbs should be cleaned and have kits installed, old gaskets/floats might disintegrate while running plugging passages partially.
Remember, this engine was made back in the late 60s, with good gas, and probably has relatively high compression. So, even if the jets are perfectly clean, the engine might need a bit more fuel at high speeds to deal with todays fuels. You may consider removing the jets, noting their size, then ordering jets .002" larger. We can help you get the correct part number for the larger jets once you have the old ones removed if you decide to go this route.
I agree with you about the intake pad under the carbs, does seem restrictive...No harm in removing it, just a noise baffle....But, the only other thing to watch out for is water spray/rooster tails when running at high speeds. The pad does help deflect some of this spray, removing it will just make it easier for water spray to enter the carbs...

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