Jet/transom angle

[Creekchub]

I’m trying to tweak my new to me boat’s performance and I’m concerned about the jet angle. There are transom wedges installed that increase the angle of the motor. I measured the angle of the transom with a carpenter square and it close to 5” which I think equals about 20 degree minus the wedge angle. Should I try to remove the wedges? The motor looks to a little low too and the motor is mounted as high as it can be on the highest holes. Maybe add a manual jack plate or other option?
Thanks

 

[JL8Jeff]

I would run the boat the way it is and see how it feels. Keep an eye on the sprayback to see if it comes over the stern. My boat is a jet tunnel hull and it would porpoise at pretty much any angle, even tucked in all the way. I had to add the transom wedges to get rid of the porpoising. So if your boat has the wedges, it might be needed. I played around with multiple heights to get the best performance and no spray back over the transom. Dou you have any good pictures showing your motor in the running position? Here's a picture of mine trimmed all the way in.

 

[Creekchub]

I’m not sure this picture is good enough to see the angle but the more I look at it the rear of the foot seems too low

 

[JL8Jeff]

Yeah, that looks like it should be a couple holes higher on the mounting bracket. It should be tucked in closer to the bottom of the boat. I went 1 hole higher on mine and got a lot more sprayback over the transom so I went back down to where it is now. That looks like it could go 2 holes higher but if it's already at the highest point, you would need to drill new mounting holes in the transom or go with some riser brackets.

https://www.amazon.com/T-H-Marine-Cmc-50012-Extension/dp/B003S8XX5A

 

[Creekchub]

Thanks for the suggestions. Much appreciated

 

[JL8Jeff]

I don't know if you can run the wedges with the riser plates so you may want to try one change at a time to see how it affects performance. If you remove the wedges and leave the motor at the current height, you may get porpoising at higher speeds which would mean you need the wedges even if you raise the motor with the riser plates. What length shaft is the motor? You might have a longshaft (20") and need a shortshaft (15") motor to be able to keep the motor installed lower on the transom. My motor is a shortshaft and even with that, it's sitting 2 to 2-1/2" above the transom to get the foot tucked in to the top of the tunnel. My boat would porpoise with the prop outboard that was on it when I got it and then it also would porpoise with the shortshaft jet. It took the wedges to get rid of the porpoising so you may run into the same situation. I think that has more to do with the weight distribution and transom angle.

 

[Creekchub]

I’m not sure the motor length but assumes
It’s 20” since my transom is 20”

 

[JL8Jeff]

I’m not sure the motor length but assumes
It’s 20” since my transom is 20”

My transom is around 23" but 20" at the tunnel and I have a short shaft jet and it's still lifted 2-1/2" at the transom. Do you have any pictures showing the motor as it's mounted at the transom.

 

[Creekchub]

Not sure this is this best picture to show my set up

 

[JL8Jeff]

That's a tough situation. If you do have a longshaft (20") motor, then it looks like a shortshaft (15") would be close to working perfectly. It's not easy finding shortshaft jets though. It looks like you would need to go up 2 holes to get the foot just under the bottom of the boat. But even with the riser brackets, you would need new holes at the bottom for sure and the top looks like the bolts would need to go through the transom cap. Unless the riser brackets have the holes countersunk and you can use counter sunk bolts to up against the transom and through the riser bracket and then the motor bracket.

 

[Creekchub]

Would a manual jack plate help raise the motor?

 

[CedarRiverScooter]

If you raise the motor anymore, please consider reinforcing the transom. There is a lot of force up high, beyond what it was designed for.

A big knee brace would be a cheap upgrade. Someone else on the site had square tubes going horizontally into the rear seat, which is even better.

 

[Creekchub]

Great idea. There is a custom jet boat company about two hours away (james river jet) I may give them a call and see if they’d be interested in some fab work and raising the motor too.
Thanks for the feedback!

 

[JL8Jeff]

You might be better off having them raise the transom by building it up. You would still need to have holes redrilled for mounting the motor in a higher position. Definitely check with them to see what they think of your current setup and what the best course of action might be.