Best pump for a conversion to single hose

tjandrews

Petty Officer 2nd Class
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Aug 4, 2007
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As detailed in another thread, I picked up a 1958 Sportwin at a garage sale a while back. I've done some work on it, and hope to get a chance to check it out on a boat soon. Assuming it's OK, I'll probably want to convert it to a single hose tank eventually. I have but one dual hose tank, and that's earmarked for use with my 1954 10HP Johnson. I have three single hose tanks, so it just makes sense to me to set things up to use one of them.

I've done one conversion already, on a 1956 15HP Johnson, but that one was easy. I already had a bypass cover from a 12HP Sea King (Gale-built) that was a perfect fit and was already tapped for a pump, so I just bought the right OMC-style pump. That one works great.

This time is different. I think finding a bypass cover will be next to impossible, so I'll probably use the drill-and-tap method, or the vacuum-cap-in-the-manifold method. I haven't decided yet. But both require the same type of pump, a more generic one, not designed to be mounted directly to the bypass cover.

My question concerns that pump. There are a LOT of them out there. Different sizes, I'm sure. Different styles and designs. Different qualities, too. I'm asking for opinions on which would be best. I'm looking for three qualities: sufficient capacity, reliability(It's gotta hold up under once-a-year use on vacation), and it needs to fit under the cowl. Cheap, no make that inexpensive, will help, too.

Thanks in advance for any help you can give me.
 

racerone

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Dec 28, 2013
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My way would be to find any pump off a small JOHNSON / EVINRUDE for less that $10 and install a new diaphragm.----Others will have a different opinion.
 

F_R

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Jul 7, 2006
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I believe the 10hp went to fuel pumps in 1959 (?) so bypass covers for 1959-63 are out there if you can find one. Trouble is, they get gobbled up by people wanting to convert.

Concerning the method, I'd suggest the drill & tap over the intake manifold way. It's just so much easier. The Mikuni pumps were very popular until somebody discovered the Briggs & Stratton one will work. I guess it is your choice.
 

Crosbyman

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I've done a few .. if you can't get a bypass cover with pump mounting holes and a pump...as suggested by Racerone & FR

​I think the next best is to mount a standard OMC over an alumuinum plate with a pulse port behind it by drilling a hole in the bypass cover and the plate just behind ... in line the pump's pulse port.... and a gasket .

​just plug the air nipple behind the carb and switch the side connector to single line see photo

..
​second best is a B&S Mikuni made round pump # 808656 with pulsing from a nippled bypass cover ....see photo plug the air nipple behind the carb and install a side single line connector

​last... Square Mikuni /nippled bypass cover .... attached the the rope starter assembly with tye wraps
 

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tjandrews

Petty Officer 2nd Class
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This is the one I did before. Like I said, the bypass cover from the junker 12HP Sea King was a perfect fit. There's another one on that old Sea King that is just the same, under one of the mounts for the fuel tank on top. So, it's too bad the garage sale find wasn't another 15/18 HP model. The 10HP cover is a different shape.
 

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Crosbyman

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here is one I did on a 5.5 (NO BYPASS COVER !!) I used the blocked air channel behind the carb plate method as shown on UTUBE using the "air" nipple
​as my new pulse source. the B&S (Mikuni made pump) was mounted on the back cross-bar using some 90 degree angles cut to fit with one "small leg" bolted to the back cross-arm and the rest were just "triangled" to support the pump using self-locking nylon nuts to stay in place.

​worked out pretty good and worked perfectly. That 5.5 trolled hours on end with no hickups.
 

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