Tracker jon boat/motor issue

I have a 15x42 Tracker Jon boat I bought new last year. I installed a 9.9 Johnson on it and noticed a issue where if I turned hard left I would get the spun prop effect, I marked it and took it back out. Off with the prop and everything still lined up. So last year I just dealt with the issue by not turning hard left issue solved. Well about a month ago I bought a 35 hp Johnson. Took some time to have a shop go threw the lower unit so it would pass a pressure test and got it back last week. Long story short I took it out Friday and had the same issue only it happens when going strait once on plane. Off with the prop marked it took it back out. Checked it, lines still lined up so I ruled a spun prob out again. Now I'm puzzled, The bottom of the boat lines up with the cavitation plate and when I was out I tried all the trim settings with no luck at all. Seems like the best setting is the one closest to the transom. Still I noticed right before it happens I'm planed out and increasing throttle to a little over half way. The cavition plate is pretty much even with the water line. I'm not sure if this is really normal but it almost seems like the motor is mounted to high because you can almost see the prop before it skips and starts reving up higher in RPMs. Seems really weird to have two different motors with the same type issue. Am I over looking something? The transom is strait on the top where the motor mounts I've noticed some are cut kinda like this ------\____/------- At this point I'm lost and really dont know what to try next. Ideas and advice would be greatly appreciated.

Short shaft motors, on a long shaft transom ?????
That would make it look like the motor is mounted too high.

Transom measures 16 3/4. Everything looks right I just measured the top of the mount to the cavition plate which turned out to be 16.5.

sounds like its " blowing out' in turns. I not a big fan those fins ,but in your case I think it would help keep the prop hooked up.

What do u mean hooked up?

k4jns said:

What do u mean hooked up?

Click to expand...

He's saying that a hydrofoil may keep the prop from ventilating.

hooked up meaning to have water to push as opposed to air.

Sounds like motor mounted to high or not trimmed right.

It could also be a bump or depression in the hull close to the stern. Is it nice and flat back there? Even 1/4" can make a difference.

An option is a jack plate. Pushing the engine back a few inches allows it to be higher in relation to the hull.

Its strait but the bottom of the boat has five ridges running from the front to back the length of the boat.... Like for water to sit in I guess... There about a inch deep could that be it?

Those are strakes.

I'm talking about a bump or depression parallel to the beam.

There's a special word for it - someone here will know.

If you are talking about a "hook in the hull" (ridge or bulge at the stern)....a hook will cause the bow to stay down when getting up on plane. Some manufacturers actually design them in, on purpose. I don't think a hook would cause what the OP is describing.

Blowing out, which is what I think the OP is describing, could be anything from too much power during the turning; the wrong prop; motor too high...and on and on.

Certainly a Doel type fin MIGHT keep water on the prop, but they have other negatives...and might not work at all.

I don't know anything about proper propping, but I'd talk to a good prop shop if I were the OP.

regards, richg99

Post a pic. showing the motor and the bottom of the transom, maybe someone can spot the problem.

A big enough dent in the bottom of your hull will cause ventilation.16 3/4" is a bit high for a shortshaft.Did someone add material to the the transom?Is it possible to lower it without cutting?If not you may need a bracket or Jackplate.I have done some experimenting with motor height and found that the highest position before it just starts to ventilate will yield the highest speeds.Even one inch of length will slow the boat.Not sure of the physics but it must be something other than just the extra resistance of a small piece of midsection below the waterline.

Maybe these pictures will help? I cant figure it out hand hate to go buying stuff if im not even sure it will help.

looks like it too high in the top pic. If the transom has not been altered,you're gonna need a jack plate to set motor back or a some kind of bracket to lower it some

No it hasn't been altered its all there with factory welds I bought the boat new. So I'm not understanding how I'm suppose to drop the motor?

k4 search this site for images of jackplates and you will see that it will allow height adjustment up and down.You may have remove or shorten clamping screws but you should be able to lower it a few inches without having clearance issues.Another solution would be to buy a longshaft parts motor swap out the shaft and mid section and raise your transom.Cheaper just to make up a jackplate.An aftermarket powertrim unit like a cmc mounted a bit lower may work as well.If you do make a plate make sure the tiller bracket and front of motor will clear transom when tilted up.Good luck mw

Having a hard time with the pics you posted. In the first, it looks like the cav plate is about an inch higher than the bottom of the boat, although the level appears crooked. The second pic looks like your setup is just about right.

So the question, in the first pic, is the level straight with the bottom of the boat? If so, your cav plate is high. If you build/buy a jackplate you shouldn't have to lower the motor as you can increase motor height with additional setback.

You're engine is too high - perhaps as much as a couple of inches.

In the second picture i agree it looks fine. In the first one, the level is strait with the bottom of the boat. When in the water it looks like the "jet" from the prop is facing up when at full speed not level either. I guess what i'm trying to say is the wake from the prop comes up like three foot from the back of the boat in a up ward direction if that makes since. If i was to convert it to a long shaft it would be way to low I believe. I've had many boats and have never noticed this. I did some reading and they say the tracker's transom is vertical rather then at any type of angle. I have no clue as to how a jack plate really works? What do I need to buy?