In cars, size .12, .15 and .18 all have the same block size and can be fitted in the same mounts as each other.
How about in marine engines, what is the biggest engine that fits in a .16 space
Namely a Kyosho .16 engine?

An .18 size engine would most like drop into the motor mount.

JD

Are 18 size engines powerfull enough?

My 16 size (standard kyosho) isn't really powerfull and doesn't get the boat to much speed.
And with a bigger prop, it can't even reach high rpm (from memory a 50mm prop with 1.6 or so pitch)

Oh yeah, they'll haul the mail! Take a lok at the Wild Thing video to get an idea of how fast an .18 will go.
With my limited experience with Kyosho .16's, I've found that they love nitro. A friend had the old Hydro-Jet (I think that what's the name was) hydroplane and one day I dumped some of my 45% into his tank, that boat really woke up!
If you're using the stock Kyosho prop, get rid of it, those things are terrible!

I swapped the prop a few times and I think 1 was a bit better but the boat never got enough speed
Going bigger/more pitch generally meant the engine couldn't rev as much
Going smaller made it rev more without really moving

I'm just thinking of maybe converting the boat to an outboard engine, where they are generally 21 sized
However it's more costly and don't know how the boat would react to so much more weight at the back

Also, at the same time, the boat I have is an inboard outdrive system, and it chews through the dogbone engagement at the back. Probably only a few hours use before I gotta change it over

what type of hull is it ?

A 50mm prop is HUGE for a .16 engine... I would think you would be looking for something 35mm or smaller.

Sean

That is a 15 engine an abs plastic hull you may get away with an 18 for a while , abs plastic has no fibers to help hold the hull together like fiberglass or carbon fiber,ect. so pumpin it up with more power will most likely kill it a little sooner.

It actually says 16 engine. The smaller kyosho boat came with a 15

The hull is a V type.
It's a fairly big boat, at 93cm long