okay, I got a 9 hp robin mud buddy longtail
I would like to keep the frame as it is in decent shape and up the Hp to something like in the 16-18 hp range.

I have read alot of post about problems with shaft size and props getting ripped out of the water. what i need to know is how big of a motor could a frame like i have handle.

just an explanation of why i want such a drastic motor size swap i just went from a bottom to a 1648 mod v and am in need of some power.

also if i do go threw with this and suggestions on prop size?

Search, this has been talked about.

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My advise, if you are buying a 16-18 briggs... get the 23 and thank me later, they are all the same block.

also i am looking at a 13.5 hp robin anyone have any idea of performance outta that size motor on a 1648 mod v. because im confident that motor would work on the frame i got

I am no speed demon i just need some power to move me another person and gear in choppy water

I had your exact setup, but I stepped up to a 23 on the 9hp frame.

How long is the drive shaft? Mine was 63".

I had to move the pivot point forward on the frame almost 3" AND bend the trim tab up a considerable amount to keep the prop under the water at full speed. Also I went with a 8.75x6 prop.