Hey guys, had owned 8 talons..got out of it and moved up North, looking at Jetboats and most guys want Sportjets for the weight savings 400 or v8 for the power! I thought wait a minute I know a motor that covers both, under 400lb and 300hp...

Welcome to the forums. While the 4g is a good platform, im not sure how it would perform in a harsh marine environment.

Im interested to see where this would go. You working with an inboard or outboard? Have you thought of the cooling, water and oil? Our motors put out a lot of heat, especially if you are trying to sustain a heavy load on the motor.

Better be a light boat, dont expect any crazy mph, at all, unless setup with a very large impeller and wait for boat to plain over and get going, and with direct drive and the load being put on the 4g, it will be in boost always, and you'd be better off with a v8 in there, would be better of with a bravo drive ( prop) instead of a jet drive (impeller),

If you decide to stay this route be prepared for many many impeller changes/ custom cut impellers, intake (bottom of boat) adjustments and shoe changes for the amount of load(amount of water) being shoved into jet drive, also a Kiel in the hull before jet drive might need to be added, to pick the boat up another inch or two

Gl on your venture!

Heat isn't a problem, jet boats are the easiest plumbed , cold lake water running through motor consistently, you will need custom tunes as well, cold coolant will basically have the stock ecu maps in cold start fuel maps


Inboard/ outboard different than jet, outboard especially considering that includes the motor and drive in one package, inboard is like a bravo drive as I stated, some gearing not direct drive

Jet is direct drive 1:1( its all in the impeller choice, and boat setup)

look at my profile pic. 18' all aluminum, heavy bottom... cooling water is NOT a problem.. there is always a constant supply of VERY cold water.

this HAS to be a JET and a 4g can make v8 torque in the same rpm range so im pretty sure it will get out of the hole!, the 2l ecotech has been used for years and does fine and its 200/180

this is not the same , but is a bit of inspiration, RB30

There's one around someone did it like 5 years ago. I Thiimk I've even seen a 4g as an outboard mounted vertically. Keep it low compression and keep the timing low and it'll hold up. If you run high rpm for long periods you'll probably need a drysump, or at least a scavenge stage for the head.

I've seen the posts with it but there's no follow up, there are a couple others where people wanted to do it and no more Posts

this is, from what i have thought of, my biggest decision. impeller selection...you don't want to be undersize and have to run higher rpm ( more fuel and wear, it's always under load) I think better to have run out of HP @6k to push any more water....my build is more torque /low end hp. BUT the question is what is a reasonable expectation of power without destroying the motor in a month
with the Hamilton its pretty easy to choose, only the 212 would work power wise.. but with the AT309 or AT312 (,http://www.americanturbine.com/information/impeller_chart_sd312.htm) it gets a bit more difficult

I can't wait to read more about this!!!

That would be a really sweet setup. I love seeing these motors crammed into different projects.