Nostalgia76

i got myself a 50th birthday present. 1998 Baja islander. Boat seems in good condition. Only issue is it sends to porpoise around 45-50 when I try to trim it up. If I trim it a little early it seems to cavitate as it tries to accelerate or starts surging and doesn’t want to go. Any help is appreciated. Sorry if this has been addressed before. I tried to search the board and couldn’t find answers.

thanks in advance.

Guess I should add. 7.3L, bravo 1 running mirage 23P “Baja” prop

AmiableDave

When it starts to porpoise. Trim it down

Nostalgia76

If I do that it starts loading up and slows down. Or starts surging like it’s cavitation or something

Nostalgia76

sometimes it seems to just load up and doesn’t want to get out of the water

bajaman

23" prop is a little ambitious, but definitely do-able depending on how strong the engine is. I had a 208 Islander, 454 power for 30 years...it much preferred a 21" prop (I ran a labbed Mirage). The 212 has a 20 degree deadrise at the transom whereas the 208 has a 17 degree...so a bit of difference there. Anyway, you may want to play around with weight distribution. On my 208 it NEVER had any porpoising issues until I added weight to the back...firstly when I added a second battery and the secondly when I installed a big cooler in the engine bay. After that, at top speed I had to deal with porpoising, couldn't trim it out, couldn't run through it. In its early days it easily ran mid to high 60s, but once the bouncing started, I never took it up much past 55 - 58 mph. That hull was a handfull at top speed anyways so...yeah.
So, play around a bit with the weight, see if it makes any difference. You might benefit from the installation of trim tabs if not on already.

Nostalgia76

Thank you. It’s got tabs but I think I need to rebuild the cylinders. Might need to redistribute weight too. Apparently big motor and full fuel tank aren’ta great combo