Merc pre alpha trim pump thread sizes help

Jakecsam

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Joined
Apr 15, 2026
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4
Okay so I have a 1980 Chris craft Catalina 25 with a Mercruiser 260 & a pre alpha drive. It has the….
66397A1 76812A4 Reverse Lock Valve Shift and the trim pump that is currently installed on the boat is a MerCruiser 79271A4. I have the two braided metal hoses ran from the outside manifold nicely, but someone has been in here before & seems to have played around. So as it sits right now I have the 2 hoses coming from inside, the 4 connected at the rams all good, a pump that works but no fittings on the pump. I was going to bypass the reverse lockout so I put some plugs into the ports on that and wanted to straight shoot the two hoses from transom right to pump, problem is there’s no fittings on the pump & I’m assuming they’re two different thread sizes. I work at a marine shop so I have tons of stuff laying around I can make work so just wanting some advice on what would be my best option ? I can still run the reverse lockout, would just like some direction possibly ? Thanks in advance.

Also I do have a set of the newer style black & grey hoses that fit into a newer style manifold on the t plate (7-16 inverted flare as opposed to the older braided ones I have that I think are 3/8)
Also have a few other different style trim pumps laying around ( I added photos to this post ) and maybe one of those could be plug and play ? But also hoping I can just get the old existing one plumped properly, seems like a spring and bearing ball might be missing any help is appreciated
 

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Bondo

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Joined
Apr 17, 2002
Messages
71,425
Ayuh,..... Welcome Aboard,...... What I'd do is use the new style plastic tank pump, the black 'n grey lines to the manifold at the transom,......
 
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