1988 30SS/31SS Porpoising
 

Hey guys was wondering if anyone can help out here. I have an 88 30SS with stock 454's that I am guessing to be the 330's. I have run both the Mirage 23p 3 and the Bravo 1 24p 4's and the boat just wants to porpoise. I have to run the trim all the way down and sometimes even tabs too if I have many ppl in the boat? Very frustrating and I don't know what fixes it? Not sure if I am just that under powered or what? Any suggestions or info would be great thanks!!

Bravo drives?
Are they properly aligned?
Is the bottem straight? You may have some rocker or hook.
Cavitation plates and skegs ok?

Yes Bravo Drives. I think they are properly alligned. I measured them once and thought they were right, but will sure check them again if you have any suggestions? I need to check to bottom to see about the hook. Cav plates seem fine and the skegs only have a little missing off the rear lower corner?

shortys will fix this problem !

I'm leaning toward a bottem issue. Are there any heavy loads in the cabin that could be throwing off the balance? Also, what speed does this happen? The 31 does porpoise at some lower speeds if given any trim. Was it better with the 4 blades?

That is what I am afraid of too. Nothing really heavy in the front. The very is used for extra life jackets, noodles, floats and couple other things, but nothing heavy. It is pretty much the same at all speeds. The only way I can get any trim out is if I tab down a pretty good bit. I am not real sure what the bottom should look like or how to check it to see either? I was told the 4 blade should help the problem, but I don't think there is much difference between the 3 and 4 blade props. Thanks again for even taking the time with this.

too much stern weight and or a rocker in the bottom of the hull . Get a long straight edge out and put against the bottom from the last 8 to 10 feet of the hull. A hook helps sucks the hull down so alot of boat manu's add them in to help a hull plane better. A rocker can add a little speed and free up some hull but can make a boat porpoise. Thats what I would check. Good luck

it could also be WATER in the foam between the floor and core !!!! the older ones had that issue with the foam !

I still say u need to run faster and lift the drives...( NOT TRIM ) lift them ( shorties ) !!

mine had SBC and alphas...did 62 MPH max..never had an issue exsept the water in the foam !

Ok great I will check that and see what it looks like. I will let y'all know what I come up with. Thanks again guys!