27gdlt. Kohler. My cav plate is bent to almost a 45 deg angle. Still running too deep, i have to put all my weight down on handle to keep it running level, prop NEVER blows out. This is my 13th longtail and never had one i couldnt make work. Boat is a 1648 seark MV, not a crawdad model. But ran great before i put blind on. Have a tach headed my way to verfiy rpms. It was running a little deep before i bent plate down but now its even deeper. Males zero sense. Anyone see something like this?

Pic?

#CFFITR
#TheGhostBoat
#whoneedsphysicsihaveamudmotor

Only pic i have on my phone. Had to grab a screenshot from a video. Ill get a better one tonight.

No you didn’t!

A better view of setup

It should definitely not be bent that far down.

What is your transom height and what is the length of your LT?

I’m going to say you have a tall transom model mounted on a short transom boat....just my guess.

Semi drawn to scale.

I’d say the shorter transom creates steeper angle of entry for the cav plate compared to ideal set up on a tall transom. But, I’m from Louisiana ... and have only owned one long tail.

according to your graph (which i got a kick out of btw, engineer by trade) my setup should run more shallow since my pivot point is closer to the water making it less of an angle. What i dont get is it was running semi deep before i built the blind on, so i bent the tab down to give me some more upward pressure. Now its running even deeper than before i bent the tab. I know the blind added some weight to my rig and shes riding a little low now but longtail shouldnt be running this deep. Im gonna verify tach numbers hopefully tomorrow to make sure im turned up enough.

I measured tonight plus checked serial number its a 72" shaft on a 15" transom.

Had a chance to talk to previous owner. He had the same issue fighting it running deep. It also causes the nose of his boat to plow and take on water. So something isnt right with this motor. Im beginning to wonder if the angle of the cavitation plate is wrong and it sits at an angle in the water causing it to dive.

That garage sure is looking tidy!

That garage sure is looking tidy!

my shop is a nightmare right now, after the blind build i havnt had a chance to pick up yet.

So i think you were on to something in your reply above. I have a 15" transom and the boat is riding low due to load. So the cavitation plate will have a forward bend when its riding just below the service causing it to want to dive. What are my options at this point?

bolt on trim tab
add pods or hunt deck to raise ass end of boat to change angle
raise transom (not a fan of this one)

had a chance to talk to Warren this morning a little bit, he thinks that my problem lies in the rpms. that the engine is overloaded with too big of a load and cant turn fast enough to get any speed.... This still doesnt account for the fact that even at slow speeds the prop wants to dive like a submarine. I dont doubt that i need to turn my rpms up but i also dont think that that aside from top speed my rpms are going to affect the prop diving that much esp in deep water. In mud if it was biting and augering down then ya.

First, start thinking two or three steps ahead....last resort would be to cut off the cav plate and put a new one on at different angle or one that you can adjust.

Just ideas here...
1. Cut slits on each side of the front of the cav plate to create tabs on the front to bend up.

2. Maybe cutting holes with a hole saw across the front of the cav plate to allow water to flow through the plate instead of forcing it down.

Either of the above could create an air bubble in front of your prop, though. Maybe a combo of 1 & 2??

Like I said, experiment with fully expecting to replace it. May figure something out.

Before making any permanent changes, bend it more, and then some more. Like Coco said though, if it got a few more RPMs and MPHs it may smooth out. I know when I load my boats way down some adjustments are required from running empty and vice versa..

I understand the loading up the engine if there's not enough power for the load, but the engine bogging has zero to do with the prop end of a longtail wanting to dive. The force of water against the cav plate or any other metal in the water, and angle of the prop has everything to do with it. The engine turning a certain rpm doesn't matter. Does your boat sit lower with the load in it? Sure. Should it cause that thing to dive? No way. I know you mentioned not wanting to build up the transom, but you need the cav plate to be less affected by the water. Bend it more or raise your transom to get the angle of attack of that plate more neutral


#CFFITR
#TheGhostBoat
#whoneedsphysicsihaveamudmotor

Take the cav plate off and try it.

here are some better pictures of my setup and on my rig:

20190730_203223.jpg

20190730_203230.jpg