My buddy has a Lowe 18x60 jon with a tunnel hull and jet outboard. He has been frustrated with the performance. I don't know anything about tunnel hulls and told him I would ask on here. I did ask him if the tunnel was vented and was told 'no'. I'm thinking from what I have read that may be his problem. He told me his motor has a five inch set back jack plate. The boat is stock as made at the factory. I believe his motor is a 90/60 hp.
Thanks

I don't know ton about tunnels but venting would be bad with a jet. Also all the jets I've seen don't run a jack plate. The foot sits right off the back of the boat. With the tunnel it will sit above the bottom of the boat.

Netman, I'm no expert by any means, but I have built a bunch of prop tunnel hulls and have had a good luck with them and a bunch of happy users.

Theres a lot of misconception on the whole vented tunnel thing. The vent in the tunnel is not really meant to do anything as far as clearing air from the water stream heading to the motor, and correcting any sort of turbulance ot cavatation issues. The vent is to break a surface friction, or vacuum that is created when a tunnel hull is running on step. The water running up the tunnel creates a difference in water pressure and the back of the boat, and actually sucks down or wants to squate at speed. The vent in the tunnel is meant to break that suction and regain the speed that you would normally loose in switching to a tunnel on an other wise simular hull.

I've never built or fooled with a tunnel for a jet foot. I do know that the manufactures build two different jets for props vs jets, with teh jet tunnel being all together different, and usually a lot less of a tunnel then on a like sized prop boat.

Is it 2" tunnel for jet or 6" for prop?

I did some research last night and seen the tunnels for a prop and a jet are totally different. I sent some links to my buddy. I cannot answer the question about the tunnel as the boat is about fifty miles away.
I believe you guys have answered the problem based on what I read last night.
Capt thanks for info on the vent. My mind was thinking of the misconception route.