Ok I'll give some more info, I have a 16' 4winns Marquis with a 75hp.
Mercury 20" transom on it. The problem is that the 75 is not enough
power for slalom skiing starts so I bought a 120hp. Johnson, the 4winns
is rated @ 125hp. Maximum. Then I found out that the Johnson has the
extra longshaft, after I bought it of course. So now I am trying to
decide what would be the best way to go in terms of cost and
performance. Any advice? I was concerned about the extra stress (if
any) on the transom from lifting the motor an extra 5" on a jack plate,
or any possible performance improvement from the Prop being further back
and away when trimmed up at speed if anyone has done this. I was also
planning on mounting the jack plate on the pre-drilled mercury transom
mounting holes thereby eliminating the need to drill more holes in the
transom. Or would it just be easier/better to find a decent used hull
with a 25" transom. Who made a 25" transom in a 16'-18' ski/fish open
or closed bow V-hull boat? If any one knows. Thanks. Tom.