Help Me! Jon Boat/Jet Ski Conversion Idea Bounce

[rogerdodger56]

I trout fish and as we all know, lower units and stationary rock do not play well together. I have a 1542 older grumman and a yamaha 650 wave runner jet drive I want to mate together.

I will take any input on these thoughts and any ideas. Very few websites on this subject provide useful info other than "look at what I did".

Here are my thoughts:

Maximum speed

I will make an aluminum framework for mounting the engine and jetpump that will bolt to the hull. The flatted hull of the jonboat will have more drag than that of a jet ski hull. If I mount the frame work on the outside of the hull, I could create a "pad" using "marine foam sandwhich" 24" +/- for reducing wetted surface underpower. Also idea considering is expanding bottom width with foam sandwhich and creating 2 "tunnels" on each side of pad to increase lift?!?!?! all of this should create a stiffer hull without extreme weight added.

Next is issue of ingesting sand/pebbles etc. Since the water intake/higher speeds is not a primary equation, if the jet pump water intake is widened and lengthened and an intake grate is fabricated can this offset the use of a grate with narrower slots. most aftermarket grates have a scoop or shovel to assist in directing water at higher speeds (my guess) but speed is not the issue. I want to minimize pebble ingestion - sand, well probably can't avoid.
If I could get 20s mph I would be happy.

As a point, the grumman has issues. It is a forward and stern deck (now to minimal framework) 5 of the ribs are fractured in half where decks were not framed out (foam sandwhich to repair). I paid little for it and it came out of florida. The previous owner must have hit EVERY oyster bar in the intercoastal and it must have leaked like a sieve 'cause every rivet on the bottom had a dollop of silicone on it. I have no clue how it planned with a 100 hershey kisses on the hull.