Outboard too high...

Bought an '84 1651 Polar Kraft and have been going through and modifying areas that needed improvements and repairs. The transom was definitely a full repair along with a bunch of leaky rivets. Anyways, after I had achieved a moderate level of water-worthiness I mounted my outboard on it and took it for a maiden voyage to see how it would do. For the most part it was great, the slight v-hull and coast guard front took the waves better than my old flat bottom and it really moves with my old Mariner 48. But, the outboard is too high. Throws around a 6' stream either side of the outboard at full speed and the tiller pulls toward the port side. No cavitation, but pretty moderate pulling force. Its been my experience that the motor is high in this condition. Problem is the outboard is sitting directly on the transom. Moving it out and down won't allow the outboard to tilt properly. Thinking my only option is to cut down into the top of the transom to lower. Any thoughts, experiences?

Sent from my SM-G973U using Tapatalk

If you need to lower it then get a transom jack. That will set it back and you should be able to mount the motor where you need it. That should also allow you to tilt the motor however you need to by raising the motor up first.

On my flat bottom jon, I tried raising the outboard from the transom by 1 inch incremental shims. Found 1" on that boat to be perfect and 2" acted like the condition I have now on the mod-v Polar Kraft...

Sent from my SM-G973U using Tapatalk

The pulling to the side could be the fin above the prop needs adjusting. Do you have the motor tilted in as far as it can go?

JL8Jeff said:

The pulling to the side could be the fin above the prop needs adjusting. Do you have the motor tilted in as far as it can go?

Click to expand...

Fin above the prop is straight back and the tilt was set to the other transom. Outboard needs to raise away from the transom 5 to 10° for the top to run flat with the water.

Sent from my SM-G973U using Tapatalk

The fin should probably be turned a little to offset the prop torque so you can make adjustments to that to see if it gets rid of your pull. Do you have any pictures showing the motor in the running position with the boat on the trailer? Were you getting any porpoising while running?

JL8Jeff said:

The fin should probably be turned a little to offset the prop torque so you can make adjustments to that to see if it gets rid of your pull. Do you have any pictures showing the motor in the running position with the boat on the trailer? Were you getting any porpoising while running?

Click to expand...

I did not take any pics of the outboard on the new boat other than on the kickstand. It was just a quick swap to try out the boat then swapped back. The pic shown is the outboard on my old boat before the swap. It works great on that boat, top is flat to the water at full speed, fin is set straight with no pulling. Its a heavy flat bottom jon. The Polar Kraft is much lighter with a bit more angle to the transom so the prop is more towards the boat. The trial run of the newer boat had close to 200lbs up front and started to porpoise when close to full speed. I will be adding more weight to the boat; decking from front to back mainly and hopefully that will cure the porpoising. Along with the fuel tank and battery under the front extended deck.

Sent from my SM-G973U using Tapatalk

This pic shows my dilemma in using anything rear of the transom to lower the outboard. Its really tight between the clamp area and the forward section to the tiller. I would have to cut out the transom anyways, I believe, so notching the transom may be my only option with this setup.

Sent from my SM-G973U using Tapatalk

The measurement from the transom + shim of my old boat is 16 ¹/²" and works great. New boat transom is 16 ³/⁴". Only real difference is 1/4" and the new boat has a full keel where the old boat has only a middle rib. Suppose the keel + the mod-v hull be making the big difference?

Sent from my SM-G973U using Tapatalk

Tough to tell with that picture and the motor tilted up. My hull is a jet tunnel so I can't compare but a 1/4" difference would make you think it should run the same. But it could be the transom angle and where you have the motor set. When I start to trim my jet out, I get a lot of spray from the foot. The cavitation plate should behave similar so if you have it trimmed out too much it will lead to spray.

Once I seal up the leaks I've found I'll set the outboard back on and take it back out to check for other leaks. I'll take more pics of the trim angle then. I'll mess with the tab also, but I tried that when I had close to the same issue with my other jon and it had no effect. It took lowering the outboard to correct the issue...

Sent from my SM-G973U using Tapatalk

Update: I did take the boat back out to check for leaks and found some more rivets leaking. I did not remount the outboard though, so no pics. However, I have acquired a different outboard. It's a '79 35hp Evinrude that's a long shaft. I definitely have some things to figure out and I'm gonna put things on hold for now. I have a couple big projects to work through first and hunting season is soon approaching. This boat will have to wait until next year...

Sent from my SM-G973U using Tapatalk

Since the weather has warmed its time to revisit this topic. I have decided to go with the long shaft Evinrude 35 to power this boat. I used a straight edge and figured out that the transom is dropped 5½" to accommodate a short shaft outboard. I mounted a temporary block of wood to the transom to simulate that mounting height for the long shaft and that put the cavitation plate fairly even with bottom of the boat. Its now ready to hit the water for testing...

Sent from my SM-G973U using Tapatalk

Got the chance to run my Polar Kraft this last weekend and the new outboard height worked perfectly. No tiller steer and a normal wake behind the boat. Got up to 27 mph with an 11 pitch prop. Plenty of power from the outboard to go up to a 13 and possibly match the speed I was getting out of the boat I just sold with the bigger outboard. I have a lot of remodeling to do, including raising the transom. I just purchased a tig welder and it's already showing its worth sealing up leaky rivets. It should help me make this boat all I want it to be.

Sent from my SM-G973U using Tapatalk

Getting the Polar Kraft a bit more set up how I want it. Done a lot of work and have a lot left to do. Fuel tank and battery are up front and the weight transfer along with my significant other/fishing partner up front also has changed how my outboard height works. The cavitation plate is now around an inch out of the water at mid to full speed and the prop pulls in some air especially on turns. I'm not gonna change the height its at just yet though. I have a bit more weight to add throughout the boat so once my build is complete I'll adjust the height then. Hopefully just a few more weeks and I'll be at that point...

Sent from my SM-G973U using Tapatalk

Glad you got your motor height issue worked out. I actually had the same problem of motor too high but already had a 20" shaft motor. I needed about 1.5" more down length to avoid ventilation at a normal tilt angle.

I installed a fixed height setback/jack plate but mounted it flipped, that is, put the normally boat side of mount on the motor side. This bought about 1" more down length, and with the setback (since it's at an angle) bought another 1" down length. Together that put the motor in a sweet spot.

The other thing I could have done was because I have Panther Tilt Unit, is mount that lower on the transom. I didn't want to drill new holes in an already old transom so tried the setback/jack plate first which worked out.

My boat has little fixes like these. I really need to do a full refurb job when time allows.

I've been trying to balance what I need to make the boat as functional as possible within the design of my build, something that money is definitely playing a factor. I wanted all aluminum hatches, but that changed to plywood because of all the other changes with my build, money and time. Now I need a starting battery, which will mount by the transom. Feeling the crunch because season as almost here...

Sent from my SM-G973U using Tapatalk

Took mine back out over the weekend to check for leaks and test my adjusted outboard height. I dropped it to 4⅞", a compromise between the two heights I've had it and a fear of going too low. This time I went alone and the outboard performed great with the cavitation plate just on top of the water. I haven't experienced any tiller steer with this outboard even too far out of the water. Weird thing is it will run at almost full throttle and I can let go of the tiller and it doesn't reduce speed (don't really care for that).

Anyways, there's no slippage or cavitation in turns, but now I have a porpoising issue above 22mph, goes 28. Not a problem with my normal fishing partner. My fuel tank, battery and anchors are all up front. Guess I'll be putting my starting battery up front also. Using all aluminum for the front deck framing to keep this boat as light as possible didn't turn out the way I expected...

Sent from my SM-G973U using Tapatalk

I reduced my leaks down to one rivet, which I fixed. Since the hull is finally leak free I installed the lower deck framing and deck. Picked up a starting battery and made a bracket to mount it up front. I also made an elevated platform for the bow for lighting. I'll try to get in another river run with it to see how it performs this weekend.

Sent from my SM-G973U using Tapatalk