What is your jet drive "sweet zone"?

[mickjetblue]

I am almost ready to start my monkey rigging raising of my "new" '99 Johnson
jet drive. Since I'll be drilling 1/2" holes, I'd like to hit the "sweet zone" on the first go.

If you can help with any info about your "sweet zone" experience, I'd greatly
appreciate it. I have to raise it 6 and 3/4" for the front lip of the intake to be exact
with the bottom of the hull, not counting the extruded fin. I'll be using 4" aluminum
angles for the new mount, and some 2" x 6" pieces as a filler across the top.

Thanks.

 

[dajohnson53]

Re: What is your jet drive "sweet zone"?

In general, you want the front lip of the intake to be just even with the bottom of the boat. You can see from the illustrations in all or most of the websites below, the engine should be trimmed so the intake is angled foward to catch the water, tucked in close to the transom.

Here's some helpful websites:

http://www.fish.state.pa.us/boatcrs/jet/jetboard.htm
http://www.scottandjenn.com/etomite/index.php?id=22
http://www.outboardjets.com/FAQ.htm
http://www.sschapterpsa.com/ramblings/outboard_jet_maintenance.htm

One disclaimer: I have a Paralift jack plate on my outboard jet. Therefore I really don't know exactly where my intake is re: the bottom of the boat. I adjust the jack plate up up for trailering and starting (to position it for the safety latch, not because of clearance), then down a little deeper to take off. I then adjust back up if need be to the "sweet spot" which is just lower than where it would start ventilating. I have a little tick on my jack plate indicator gauge and I pretty much set it at the same spot every time. Maybe one of these days, I'll check to see where that actually is. But with the large setback, I doubt if my sweet spot is the same as a conventional transom mount. I also adjust the trim a little, although now I pretty much keep it tucked in.

The Paralift is not ideal for an outboard jet - it causes quite a bit of setback (about a foot), which I don't think is optimal for an outboard jet. It came with my boat/motor and I think the rig was originally set up for a prop (I have the prop lower unit too). If I had it to do over, I'd get a conventional jack plate that only has 3-4 inches of set back. A manual one would probably work fine because after you get it set up, it doesn't need to be moved for trailering or operation.