First off ... Welcome to MGB
Please take my statements as just some free wisdom and general FYI from near 35 years running R/C boats
The Homelite engines were for a spell ( Late 1980's - late 90's )used widely in the R/C boat world. These past 10+ years they have all but disappeared from the market replaced by Zenoahs and others.
* Last STRONGHOLD for there use was WAREHOUSE HOBBIES and they may very well still have some support / parts for doing the marine conversions, exhausts etc ....
*** Go to this sites home page and CLICK on the WHH banner ad to go to there site ***
Generally engines SUCH AS THE HOMELITE having a BIG flywheel fan at PTO end make that engine sit MUCH TOO TALL in a shallow engine bay hull such as a cat.
Better suited to a V shaped engine area like a Mono hull where they will mount lower.
POWER ... yes POWER is where these last 15 years of engine tech within the R/C boat hobby has left the 11,000 Rpm sub 2HP Homelites ( Modified ) in the dust of the more compact Zenoah or RCMK engines making near 4HP out of the box and +/- 6Hp once modified. Stock @ 16,000 and @ 18,000+ rpm range modified.
Talk with TONY at WHH and see what he can do for you, Homelite power for a first boat is just fine !! ... Just not much info or support around for them these days
Regards,
Scott