Severe Porpoising Need help fast

[dazk14]

Re: Severe Porpoising Need help fast

The Amita4 is aluminum and ~$112 at iboats.

It should be able to turn a larger pitch prop, however we don't know how much load you are carrying.

Start with the free foil and see if you can get the boat to settle down a bit.

 

[Budget33]

Re: Severe Porpoising Need help fast

Thanks for your help Dazk14, I will try the foil first. Typical load is 4 adults and 5 small kids, haha. then someone out of the bunch is tubing sometimes 2 tubes. So def looking for power vs all out speed

 

[QC]

Re: Severe Porpoising Need help fast

finally some direction,

If direction is a foil, then I am very concerned considering your lower unit is already too low. But I hate foils, so I am not objective. May actually work though.

Remember the direction to check the straightness of your bottom? You should still heed that

 

[jestor68]

Re: Severe Porpoising Need help fast

Might one of these wedges help to get more trim in if there isn't enough angle in the transom?

 

[QC]

Re: Severe Porpoising Need help fast

Good thought ^^^^^

 

[JimS123]

Re: Severe Porpoising Need help fast

It looks like the bottom bolt is bottomed out . You would have to drill that hole higher to lift the motor . I think ..
As mentioned straight edge the hull to the vent plate and see exactly what ya got .. I have a little porpoising problem myself so I am very interested on how you get this solved ..

Yup, I missed that, The bottom hole was not properly drilled in the first place. There should be enough flexibility to use all 4 top holes.

OMC designed their motor mounts with 3/4" between holes. The top hole should put the motor flat on the transom. Don't underestimate the magnitude of the differences. The last outboard I had was run in all 4 holes, each time charting the speed, rpm and doing a full performance curve at each position. The sweet spot is usually somewhere in the middle. Unfortunately, it takes a lot of work to do the evaluations.

I am a firm believer of foils, and have used them on numerous boats since they were first invented. Three of my boats currently run DoelFins. For your circumstances, don't even waste the time. Its not what you need.

 

[Budget33]

Re: Severe Porpoising Need help fast

QC, I did check the bottom of the boat, its straight.

Jim, I also had a foil on my last boat and loved it, I can get one for free so won't be a total waste. What would be your suggestion for a first step? Trim tabs?

Also there seems to be difference of opinion on which way the motor should go, up or down?

 

[roscoe]

Re: Severe Porpoising Need help fast

Remember, the lead edge of that foiled needs to be above the water when on plane, just like the anti ventilation plate.

So the motor needs to go up.

 

[QC]

Re: Severe Porpoising Need help fast

QC, I did check the bottom of the boat, its straight.

Sorry, just went back and I had missed that. Post #29.

 

[Budget33]

Re: Severe Porpoising Need help fast

Qc, no worries

I'll get a look today to see if I can raise the motor the 1 bolt hole. I'm not sure if there is enough room for my steering linkage where it comes through the side of the boat

 

[Budget33]

Hi All,

Sorry to bring this back from last year but wanted to give an update. I installed a hydrofoil and tested the boat last friday. Wow! what a difference, with just me in the boat the porpoising is gone!, very happy. I only had enough time to test the boat for about 20 mins but with the engine trimmed down all the way the issue is gone. I will be doing more testing this Sunday so I will update further. Also, I made no other modifications except for the hydrofoil.