Porpoising Boat

[jwd22782]

I just purchace a 1860 lowe roughneck with an Evenrude 90 Jet outboard. The center console is in the middle of the boat. With a heavier passenger sitting in front of the console it rides fine. But by myself or if passengers sit next to me it porpoices pretty rough. Any suggestions on fixing? It also has a tunnel hull.

 

[jwd22782]

It is trimmed down all the way and has sponson pods that are about 1/2" above the bottom of the hull.

 

[Scott Danforth]

Throw a cooler in the front, or get wedge shims

 

[jimmbo]

Move any movable weight, gas tanks, anchour, further forward. Tunnel Hull, do you mean Catamaran? Tunnel Hull was often used to describe a type of racing hull.

 

[jwd22782]

Scott,Ok if I need to add wedge shims how to I attach them? It runs good with all the gear weighing down the front but if I need to go light its a little scary for me! So how would you attach the Shims. I have some and was told to use an apoxy. Could I just Drill them into the sponson pods?

 

[Scott Danforth]

They clamp under the motor transom clamp

 

[ondarvr]

Jets don't normally have porpoising issues because there's very little bow lift, but the tunnel can cause unusual problems.

​Make sure the motor can trim all the way down, there can be an adjustable bar that limits its movement down.

​Check the bottom and make sure it's flat, if it's bent in it may cause odd problems.

​And like others have said, move anything forward, battery, cooler, anchor, lunch, anything. You should have a tool box, they're never light, put it up there.

 

[QBhoy]

Can you adjust the trim angle of the jet nozzle like traditional jet drives (like Hamilton etc) ?

 

[jwd22782]

The marine dealer I bought the boat from tunned the nozzle to where it sits barely below the top of the tunnel. So I could get the most power out of the boat. The sponson pods in the back ride just above the bottom of the boat like 1/4". Can trim tabs be used with the sponson pods or should the pods be removed?

 

[ondarvr]

Can you adjust the trim angle of the jet nozzle like traditional jet drives (like Hamilton etc) ?

It's an outboard.

 

[ondarvr]

The marine dealer I bought the boat from tunned the nozzle to where it sits barely below the top of the tunnel. So I could get the most power out of the boat. The sponson pods in the back ride just above the bottom of the boat like 1/4". Can trim tabs be used with the sponson pods or should the pods be removed?

​All he did was set the motor height, you still need to set the trim correctly, yes trim tabs can be used, but motor trim comes first.

 

[jwd22782]

There is 6 positions for the trim height but there no pin in any position hole.

 

[ondarvr]

And do you have it trimmed all the way down?

​If the transom is too vertical then it will limit the amount trim in the down position, this is where the shims or wedges come into play, they are placed between the motor and the transom so the surface has more of an angle, this allows for more travel in the down direction..

 

[jwd22782]

Yes it is trimmed all the way down. It is an outboard. The jet intake is angled up towards the boat I'd say about 20 degree angel. I am taking it out this weekend again and will try the added weight in the front but if that still doesn't work I will try the shims. Thanks for all the info.

 

[aspeck]

No Title

Here is an example of a transom shim and how it is installed. This is probably the way you will need to go ...

 

[ondarvr]

Yes it is trimmed all the way down. It is an outboard. The jet intake is angled up towards the boat I'd say about 20 degree angel. I am taking it out this weekend again and will try the added weight in the front but if that still doesn't work I will try the shims. Thanks for all the info.

​The intake will always be at an angle like that, it's the output nozzle that matters, it should point down slightly.

 

[QBhoy]

It's an outboard.

Understood...but it's a jet drive.
Not too familiar with the outboard/jet propulsion, but thought is may have a nozzle adjustment ? Was worth the question....please excuse my ignorance. It will be unfamiliar to most, I'm sure.