OMC, wouldn't this be better? 1954 bigtwin 25

[kodibass]

I have read several post about fuel pump conversions, Mikuni type pumps--, briggs type pumps-- bypass replacement etc. Well I was digging through my OMC parts pile and found this pump, Isn't it the same basic design as the other two? I cannot remember what it came off but I think it was a late 80's 35 hp Evinrude, I pulled the intake cover on my 1954 25 hp Bigtwin Auqasonic and plugged one of the channels and will run a pulse hose to the pump, I have seen several post asking will a Mikuni type pump deliver enough fuel to run the bigtwins, I think this pump should. I have come across a few of these 3 line OMC pumps. Am I missing something here?

 

[Mas]

Re: OMC, wouldn't this be better? 1954 bigtwin 25

The newer OMC pump might be too big to allow the hood to close??

Mas

 

[1946Zephyr]

Re: OMC, wouldn't this be better? 1954 bigtwin 25

If you can get the pump to mount on the bypass cover, you should be okay. The '54 Big Twin doesn't have the hood that closes. It has the halves that attach by screws, individually. The re-closable hoods, didn't appear on the Big Twins/RD's until 1955. There were other big changes to the shrouding, mid-sections and lower units in '55 as well. If the bypass covers were the same from '54 to '55, then you could mount a bypass cover from a 28hp of the early 60's with a factory fuel pump. If not, then there are posts here where people have mounted factory fuel pumps on the bypass cover, by adding a plate, between the bypass cover and fuel pump. Or, you can drill and tap a hole in the bypass cover and install an elbow fitting and mount the fuel pump elsewhere on the powerhead. That option will leave you open for just about any kind of fuel pump you want.

 

[HighTrim]

Re: OMC, wouldn't this be better? 1954 bigtwin 25

Any of those pumps will deliver enough fuel, remember all they do is fill the fuel bowl, which lasts a while on its own.

I have use Mikunis, the bigger/older OMC pumps, and the newer small ones from the 9.9/15s. The main thing is how you want it mounted and how much room you have. I personally feel it is best to use a factory one on the bypass cover, but if funds/access to one limits you, or if you are doing a 5.5, there is nothing wrong with the Mikunis.

There is a member on here that makes an adaptor plate too if you want to go that route.

 

[kodibass]

Re: OMC, wouldn't this be better? 1954 bigtwin 25

Yea' I'm thinking the mikuni just because its smaller, Mine has the hood that comes in 2 halves and screws together It also has a crack in one of the halves but still screws together somewhat. I'm missing the spark plug cover so I'll make one , Also mine does not have any kind of cowling pan (?) Is this normal or is something missing (?). Then I just did the points/condenser and noticed there is no stop switch. I will post some photos soon, It has the kooooolest throttle / tiller system I have ever seen! cheers