Formula boat porpoising

[iw8surf]

Originally Posted by BroadHopper

The only time my bird do that is when the outdrive tab is too high. I would lower the outdrive tab until the boat attitude is fine. Normally I use the trim tabs to level the boat. Or create a bigger wake for surfing. Both trims all the way down.
When taking off the outdrive tab is down to keep the bow down. When I hit speed, I normally raise the outdrive tab until there is an increase in rpm. Rarely do I trim to the point of porpoising. If I do I back down.
I only use the trim tabs to level the boat from Port to starboard. Sometimes if I have a lot of people and full tank, trim tabs all the way down can help you get out the hole.
Since you have the Bravo III I suspect you have a lot of torque (6 blades vs 3). I have driven Formula SS with Bravo III and never porpoise.
I have a Bravo II. I switched from 3 blades to 4 with much better overall performance. I urged anyone with a 3 blade to upgrade to 4.

We are surfing behind a Formula?

[Bootkie2]

You are not crazy. The trim on the 270 is VERY sensitive.

The porpoising has been documented on BoatTest when they reviewed the 270

CTRL-F "porpoise"

https://www.boattest.com/oem/386/boats/3651/0/

[XCR-700]

Originally Posted by Bootkie2

You are not crazy. The trim on the 270 is VERY sensitive.

The porpoising has been documented on BoatTest when they reviewed the 270

CTRL-F "porpoise"

https://www.boattest.com/oem/386/boats/3651/0/

Well I think we have clearly established its just how this boat runs as delivered.

A better trim gauge would have helped me better understand whats going on, and I plan to share that with Formula.

I also cant help but wonder if a different prop set would have any impact.

As BroadHopper said a few posts back, in a regular single prop Bravo drive switching from a 3 blade to a 4 blade prop is well worth the cost. Wondering if its the same with a 2 prop Bravo III drive. Its a big expense to change 2 props but if the end result is a noticeable change I might be willing to pop for it.

[Woody38]

Not that there is any connection to the present problem. Several decades ago on Cape Cod I knew someone with this happening. I don't remember the make of boat, however, they added an extension of several inches, possibly 6", to the hull. The situation was resolved. I do not know but the boat may have been stored incorrectly causing warping of the hull. Weird.

__________________________________

I am a retired workaholic and continuing aquaholic

[Bootkie2]

I'm not sure a new prop set up would yield a big difference. The 8.2 with B3 out of the box is already a great pairing for that boat. What you've got here has more to do with the engineering/design of the boat itself.

I hear you though. I would be frustrated too if the Gauge showed a very low trim position and she was still porpoising (or close to it).

There were already a few comments about the sender/limit switch. +Another Vote for checking the sender. You could have the dealer check and re-calibrate the trim sender. That could possibly help you gain some better readings on the gauge. Those sender units are notoriously crappy (break all the time). Something could be going on there (even at 35 hrs).

[Descant]

OK. I'm not a Formula guy,but it now sounds like a hull/drive mismatch that can be overcome by very careful use of trim. "C'est possible?"

[XCR-700]

Hummm,,,, Based on what I have learned from you all and other reading, it appears to be a case of a different hull than I have had in the past, and learning to drive this particular hull.
It also appears that Formulas run more hull in the water/wet than other brands, and that appears to be by design. Which is fine now that I know it, and as a plus, it makes for a very good/very solid ride in Winnipesaukee weekend water conditions. It is clearly slower than other brands, which surprises me given the 8.2 Mag engine but it is also a long and heavy boat with no creaking and rattling that I have seen in other boats. So I guess these are trade-offs and with the Winnipesaukee speed limit and the way we use our boats I don’t need 50+ MPH speed, so not being a high speed boat is not a problem for me. Sounds funny even saying that as I recall when 35 or 40 MPH was fast ;-) Guess times change.

It does appear to be a poor selection of trim gauge, as the gauge range is too wide and does not best display the limited trim range this hull allows.

And I still wonder how Bravo 3 drives respond to aftermarket prop upgrades? Is it similar to other drives, or not worth the cost???

Thanks to all for your thoughtful insight

[Taz]

Originally Posted by Bootkie2

You are not crazy. The trim on the 270 is VERY sensitive.

The porpoising has been documented on BoatTest when they reviewed the 270

CTRL-F "porpoise"

https://www.boattest.com/oem/386/boats/3651/0/

It did not appear in photos and reading BoatTest that it has a stepped hull but based on the BoatTest write up as previously mentioned it appears this hull acts like a stepped hull in that very little trim is needed or should be used.

[Dave R]

Originally Posted by Taz

It did not appear in photos and reading BoatTest that it has a stepped hull but based on the BoatTest write up as previously mentioned it appears this hull acts like a stepped hull in that very little trim is needed or should be used.

I had two boats with stepped hulls and the single prop one liked plenty of trim with the a high lift 4 blade prop. The one with a Bravo 3 liked about 20% positive trim but was not very sensitive to trim.