Help with outboard set-up on transom

[RRocket]

First, I'd like to say how grateful I feel to have found this forum! I am dealing with this from a position of ignorance; I've never had to adjust much of anything on any watercraft I've operated. So now that I have to, I'm totally clueless! I am hopeful some of the experts here can guide me to where I need to be since the local "experts" seem to know as little as I.

DETAILS: My boat is a Scout 365. It's similar to a Ka-Boat I'd say. The transom height from factory is 12". My Suzuki DF2.5hp has a transom top-to-cavitation plate distance of 17.5" despite being a short shaft. So that would put the cavitation plate 5.5" below the water, which is too deep per the outboard owners manual which calls for 0-1" below.

WHAT I DID: I asked for some advice from various locations and how to get a more appropriate depth. It would seem I'd need to make a riser. Which I did. A small issue with asking the local "experts" was whether the cavitation plate measurement should be from 0-1" below the TRANSOM or below the PONTOONS, which are the absolute bottom of the boat. Opinion was 50/50! So I went with BOTTOM OF PONTOON.

RESULTS: The transom turned out well and looks OEM. See images. This puts the outboard cavitation plate .25-.375" below the pontoons. For further troubleshooting reference, this puts the same plate approximately 2" below the transom. So not a great deal of difference between bottom of transom and absolute bottom of boat/pontoons.

At up to 1/3 throttle, boat runs 8km/h. Beyond and at full throttle..no change. Bow rides high. Boat not planing. Not a sharp, beautiful wake behind boat.

Now I understand this boat/motor combo isn't meant for speed. But similar boats with same power reach nearly 15km/h when they are planed out.

My question is...what now? I'm clueless how to proceed to "fix" this. Lower engine? Raise engine? Hydrofoil installed on cavitation plate? Go on a diet? LOL [emoji38] I'm 185lbs and realize having more weight forward is helpful.

Any ideas?? Also not sure if this post is more appropriate in General or Motor forum.

Thanks so much for any insight!!

[paintman]

Too much weight aft? If you look at their own video it shows the driver well forward & using a long tiller extension.
https://scoutinflatables.com/products/scout-365 on the 'Product' page.

Outboard trimmed too far out?

Outboard too small? Again, for your boat their site shows maximum size of 3.5hp and recommended size 3.5hp.

[Blankton]

2.5hp is very small. I've not heard of much planing with that kind of motor. Do you have examples of that boat planing with that size motor?

All of the messing baout with transom height etc will only become beneficial if improving the planing behaviour. At displacement speeds it won't make much odds and I'm not convinced that engine can get you on the plane, especially if you weigh 185lbs.

You could try a tiller extension and get well forward. Before Wasing any more money you could try a diy one with a bit of old waste pipe.

[lightning]

You're going to struggle to get that boat planing with a 2.5hp

l have a Zodiac 285s with a solid floor/air keel. With my Mariner 6hp the boat would plane, but it took a bit of effort to get going. Once planing however it would achieve around 14mph.

To get the boat planing l had to use full throttle on the 6hp and it took a few seconds to get past the 6mph "hole"

So with a 2.5hp l imagine you'd have to have absolutely ideal conditions and it might do it if you are lucky.

[RRocket]

Based on my (minimal) knowledge of this, it seemed I needed less angle on the outboard to get the prop closer to the transom to alleviate the bow high attitude.

So I made a "wedge" to sit at the top thereby pushing the prop closer to transom. I also moved slightly forward in the boat.

And voila! 18km/h with my 2.5hp! I also have a hydrofoil ordered for the cavitation plate. Am excited to see if that helps.

I really am thankful for all the replies.

[RRocket]

Installed hydrofoil today. It's quite large!

Have not tested yet.