Formula boat porpoising

[LIforrelaxin]

Go out on a calm day, start with the tabs all the way up, to take them out of the equation..... The get up on plane and go to about 3500 rpm... that is where most people tend to cruise... then slowly trim the boat up, see how it re-acts, the the tabs up and out of play, you should find the balance point, where the bow will bounce with the least little ripple.... Once you find that point, trim back down a little, and that is likely where you want the drive when you out and about...

Then put the trim tabs back into play, and use them as your supposed to, to control the attitude of the boat for the given conditions....

Tabs and trim on the drives are for different things, most people don't know how to use them in conjunction with each other... so the best thing is to find where you want the drive, and leave it there, and use the tabs to adjust the boat from then on out.....

[8gv]

What about the trim limit switch and trim gauge possibly being out of adjustment?

Maybe the tucked in setting is still 2°-3° to far up.

Starting there it doesn't take much more trim to reach the porpoise point.

I suspect there is a way of measuring this.

[TiltonBB]

I am surprised that anyone would operate an outboard or I/O boat without making trim adjustments on the drive. I use mine constantly.

When bringing the boat to cruising speed I always leave the drive down. Once I have an established speed I lift the drive so that the bow will rise. This accomplishes two things: Your speed and RPM will increase slightly with the same throttle setting and the ride will be much softer since the bow is not hitting every wave you cross. Generally, it will bring about the front third of the boat out of the water and your MPG will increase with less drag.

I only use the trim tabs to keep the right/left attitude of the boat level and the necessity for that depends greatly on the loading of the boat. The best setting for the trim tabs is all the way up to eliminate drag on the boat. The ability to do that depends greatly on the loading and the hull design.

I realize that everyone has their own way of doing things but this is what has always worked for me over the last 50 years and about 15 boats from 18 to 34 feet. (Two were jet boats and you can ignore using a lot of your experience with a jet boat)

[XCR-700]

Originally Posted by TiltonBB

I am surprised that anyone would operate an outboard or I/O boat without making trim adjustments on the drive. I use mine constantly.

When bringing the boat to cruising speed I always leave the drive down. Once I have an established speed I lift the drive so that the bow will rise. This accomplishes two things: Your speed and RPM will increase slightly with the same throttle setting and the ride will be much softer since the bow is not hitting every wave you cross. Generally, it will bring about the front third of the boat out of the water and your MPG will increase with less drag.

I only use the trim tabs to keep the right/left attitude of the boat level and the necessity for that depends greatly on the loading of the boat. The best setting for the trim tabs is all the way up to eliminate drag on the boat. The ability to do that depends greatly on the loading and the hull design.

I realize that everyone has their own way of doing things but this is what has always worked for me over the last 50 years and about 15 boats from 18 to 34 feet. (Two were jet boats and you can ignore using a lot of your experience with a jet boat)

Very similar to my experience and thoughts.

Well stated!

Thanks for the reality check.

[XCR-700]

Originally Posted by 8gv

What about the trim limit switch and trim gauge possibly being out of adjustment?

Maybe the tucked in setting is still 2°-3° to far up.

Starting there it doesn't take much more trim to reach the porpoise point.

I suspect there is a way of measuring this.

I dont think there is a problem, its more of a perception issue of how limited the range is that this boat runs well in.

Older/smaller/less powerful/differently designed boats seem to allow/tolerate a wider range of outdrive trim, and it appears this one runs in a narrow range.

But I think you are on to something in that maybe Formuls should be looking for a trim gauge that better displays the useful range for this boat. The gauge in my boat is clearly suited for a different boat that allows/tolerates a wider trim range. its basically a worthless gauge as it doesnt display useful information, the range of trim movement displayed is almost impermeable.

So maybe in reality you have helpped me better understand part of my concern, I'm in part basing part of my original concern on what I see in the gauge, very little movement on a gauge with a wide potential range. Like putting a 20,000 RPM tach on a motor that mostly runs under 4000 RPM. Not super use/helpful.

Thanks

[XCR-700]

Originally Posted by LIforrelaxin

Go out on a calm day, start with the tabs all the way up, to take them out of the equation..... The get up on plane and go to about 3500 rpm... that is where most people tend to cruise... then slowly trim the boat up, see how it re-acts, the the tabs up and out of play, you should find the balance point, where the bow will bounce with the least little ripple.... Once you find that point, trim back down a little, and that is likely where you want the drive when you out and about...

Then put the trim tabs back into play, and use them as your supposed to, to control the attitude of the boat for the given conditions....

Tabs and trim on the drives are for different things, most people don't know how to use them in conjunction with each other... so the best thing is to find where you want the drive, and leave it there, and use the tabs to adjust the boat from then on out.....

This is exactly what I did.

What surprises me is how how little trim up this boat will tolerate.

Most boats I have driven never porpoise, you will simply just over trim an lose performance.

Clearly the combination of hull design, length, power and the ability to transmit that power into thrust have created the ability in this boat to porpoise.

Also it appears that Formula has picked an engine/outdrive angle that is very neutral. It neither allows you trim down to an angle that lets you plant the nose in really rough water, nor does it appear to need much trim up to reach the designed planing attitude.

No complaints, just not what I have experienced in the past and seems interesting/unusual to me, as most boat I have driven usually have a pretty wide range of trim they operate/tolerate. I honestly have no reasonable basis to say if this is common or uncommon, I only know what I have see personally and for my this is a different experience. And the experience that MeredithMan describes is pretty much how our boat performed, so it would seem to me there is nothing wrong with my boat per se, nor my surprise by the way it performed compared to my personal past experience.

Thanks!

[LIforrelaxin]

Originally Posted by XCR-700

This is exactly what I did.

What surprises me is how how little trim up this boat will tolerate.

Most boats I have driven never porpoise, you will simply just over trim an lose performance.

Clearly the combination of hull design, length, power and the ability to transmit that power into thrust have created the ability in this boat to porpoise.

Also it appears that Formula has picked an engine/outdrive angle that is very neutral. It neither allows you trim down to an angle that lets you plant the nose in really rough water, nor does it appear to need much trim up to reach the designed planing attitude.

No complaints, just not what I have experienced in the past and seems interesting/unusual to me, as most boat I have driven usually have a pretty wide range of trim they operate/tolerate. I honestly have no reasonable basis to say if this is common or uncommon, I only know what I have see personally and for my this is a different experience. And the experience that MeredithMan describes is pretty much how our boat performed, so it would seem to me there is nothing wrong with my boat per se, nor my surprise by the way it performed compared to my personal past experience.

Thanks!

Sounds to me that Formula has taken the stance that most people buying their boats, don't have a clue as to how to trim and adjust the handling of their boats. Thus, they have made things harder on those that understand how to make a boat perform they way we want.....

What this means, is that to really be able to trim and control the handling of your boat, you need to make more drastic adjustments, so that you get proper trim response... the problem is that would start to void a new boat warranty....

I would talk to a dealership or two, and see what can be done... The wrong answer from a dealership would be, "it is what it is"..........

Sounds to me, the the drive isn't really properly placed, thus you are porposing, because, you boat is riding on the hull further up, and the cavitation plate of the drive, instead of the rear pads of the hull, like it should....