Keene upgrade from 5” to 6”?

Aquatek · May 25, 2025

Hi everyone,
We are converting an old 5” Keene single motor dredge to a 6” and I was wondering if anyone has a recommendation for engine/pump size? We have the chance of a Honda GX390 at 11.7hp but is that enough power? The pics below are as it is presently (5”).
Thanks,
John

russau · May 25, 2025

What pump (GPM) goes with that eng.? and normally what depth are you going to be diving in and the length of hose you will be using normally ?

Aquatek · May 25, 2025

russau said:
What pump (GPM) goes with that eng.? and normally what depth are you going to be diving in and the length of hose you will be using normally ?

It’s not my dredge so i’m just checking on what pump we’re using. The river is max 6 feet and the hose is 20’ which is good! Soon as I can get the pump size i’ll get back. From what i’m reading it seems the GX390 might be a little light 🤔

Aquatek · May 25, 2025

Ok, we are running a P350 in 5” mode on a 9hp honda and it works well in the 6’ depth.

russau · May 25, 2025

with your engine that you stated and your P350 pump you should be good to go! It appears that (with your picture) you will need a water heater & air . that snow on the bank looks cold !

N-Lionberger · May 27, 2025

Yeah you should be fine with that motor at 6 feet.

Aquatek · May 28, 2025

russau said:
with your engine that you stated and your P350 pump you should be good to go! It appears that (with your picture) you will need a water heater & air . that snow on the bank looks cold !

I was doing 4hrs and with my drysuit I was fine 👍

russau · Aug 29, 2026

Thats a fine looking rig you have there and she enjoy the update and get back to being used ! I sure wish I was U with her !!!!! Post some pics of her in used and your gold !GOOD LUCK !!

russau · Aug 29, 2026

russau said:
Thats a fine looking rig you have there and she enjoy the update and get back to being used ! I sure wish I was U with her !!!!! Post some pics of her in used and your gold !GOOD LUCK !!

I was building a 5 inch when "my plug" got pulled and ended my days of glory! You can't imagine how bad I miss it now that I can't do it any more !!!

Quinc · Sep 8, 2026

If the engine needs a little more power there are some simple mods you can do for 20-30% more power while keeping the governor in tact. Thinner head gasket, advanced the timing 4 degrees with an offset flywheel key. Ditch the stock air filter setup and use a velocity stack with open element filter, exhaust header with high flow muffler (or no muffler if sound is not an issue) and if you still need some power you can get a midrange camshaft. Then jet accordingly.