Porpoising - 311
 

Morning folks!

Another great weekend in the books! We went to Harborfest, and enjoyed friends, food, and boats; fireworks for the finale! Yesterday was set up for cleanup and rest. Surprisingly, the boat stayed pretty clean despite three young kids with food and drink, as well as guests coming onboard while we were anchored for the show... we had a full boat!

So yesterday I had the boat to myself (we overnighted the boat local to Harborfest), and got to play around some without having to worry about the kids getting banged up. Overall I had fun, but man does she porpoise! Trying to get her trimmed out is where I'm running into problems.

I have marked my indicators so that know where neutral is with regard to trim and tab position. Neutral trim is at 5/6 mark, and tabs are on 3. These indicate a position that is on the same plane as the hull bottom.

Typically, I'll leave the drives tucked in and tabs set at 3 unless I need to get on plane quickly (I'll drop them to 9 and bring them back to 3 once going). Generally. she gets on plane without much trouble (though dropping the tabs. Keeps the bow low so I can see). Once on plane, I'll bring the trim to 2/3 and leave there because she'll start to bounce as you go up in trim. The porpoise gets so bad that the boat will leave the water (see pic below).

Is it normal to run the 311 with negative trim most of the time? I would think she'd want a little positive trim to run best. Negative trim puts the bow in the water leading to bow steering (a very unsettling feeling).

502 MPIs with CMIs, 300 hours, TRS drives with nose cones, 27P Mirages. RPM at WOT is 4700-4800 depending on load.

Should I add some weight up in the bow?

At what speeds are you talking about when porpoising?

Cruise... 3K to 4K. I've been running on the ICW here lately so running WOT hasn't been an option because of traffic.

TomZ,

These are the same props from the CBFF run, correct?

My 292 (Modified 454 Mags w/ Bravo's and 26P B1 Props) loves to porpoise and will do so if not constantly adjusting trim/throttle during operation. I have been able to find the "sweet spots" and the corrections needed to quickly calm her down. Although your 311 is obviously longer and heavier, both boats have a lot of weight towards the rear. The following is my typical "settings"

Tabs - Never used them, ever. So i can't give any input here.

Planing - Drives tucked in, on plane around 2600 RPM in very short time.

Cruising with some chop - Drives at 2, engines at 3000 RPM

Cruising (95% of the time) - Drives at 3.5, engines at 3600 @ 50 MPH

WOT - Drives trimmed out a hair off the indicator and one blip back In on the switch, engine at 4900 @ 70 MPH (Fully loaded yesterday, 135 Gallons, Coolers, 7 people)


I will use 3600 RPM as my example because I am typically at that RPM..

My porpoising occurs if I trim up too fast without clicking up the throttles a bit (up to around 3600). I alternate a burst on the trim switch, with a click on the sticks until I reached my desired trim and RPM. If I trim from full tucked to 3 or 4 without moving the sticks, she starts jumping pretty good. If I start to feel the porpoise while I am cruising, I will raise the RPMs by a couple hundred and bring it back to 3600 or trim it IN briefly then back OUT.

Porpoise Mode is activated more easily if I trim anywhere past 5 below 4000 RPM. If i am above 4000 RPM and I trim out from 3.5, the boat really opens up around 5/6 on the indicators and pulls hard to WOT.

Apologies for all that information, but that has been my experience so far. My 292 takes some driving to keep the ride smooth but I enjoy making adjustments while cruising. I have put ~30 Hours on my boat so far this season so I have had a lot of seat time to get everything figured out with my setup. Coming from the 223 to the 292, there was a little bit of a learning curve but I am sure others will post their experience with these old birds.

At WOT in chop I can trim her out and run hard for the most part, but even just under WOT the porpoise is there. Video link below is running about 43-4400, trim about 5/6 if I remember correctly.


https://m.youtube.com/watch?v=UBOqoD...ature=youtu.be

If all the way down is zero neutral shouldnt be at 6, its about 3.5 on mine, same with tabs.

anyway, for me 3k i run about 1.5-2 on drives, no tab. From there its more trim with more rpms up to about 7 or 8 wide open still no tab.
if im running through heavy chop and rough water i put the tabs at 3 or so maybe more if real rough, also may use one tab in strong crosswinds.
no porpoise issues.

Josh, your experience is similar to mine. And yes, same props as the run. Stacy and I got 69.8 out of the GPS speedo and Navionics spinning to 4800 so I'm pretty happy with them (though they do need a little cleanup).

My thing is that once the porpoising starts it's hard to get her to stop without tucking the drives back in a good bit. Perhaps more seat time will help.

My understanding is that the 311 has rocker built into the hull. Maybe that's contributing to the negative trim needed for cruise. I'll need to read up on that aspect.

We used a straight edge to gauge neutral trim angle... the cavitation plates were in plane with the hull's running surface at 5/6.

Maybe I'm wrong with what's considered neutral?

Interesting question...

Is drive trim angle set by the hull's running surface, or by its waterline? And how does the 311's rocker play into this? I'm guessing the porpoising has a bit to do with it.

The 311 doesnt have rocker, its a straight bottom hull. The 272, 242, 206 have it.
Do your indicators read zero when the drives are tucked in? Both my 272 and 311 all were neutral at about 3-3.5 both tabs and drives.
I do think you are over trimmed thats why you are porpoising, with a gps nudge them up till you stop gaining speed you should be good to go. Some water in the bow tank can help the ride.

I've read that the 311 has a light rocker (opposite of the hook on the smaller hulls). Maybe the information was wrong, who knows.

My indicators for the trim do not go to 0... they're adjusted so that they're on the hash mark between 0 and 1 (maybe a little closer to 1). She was like the this when I got her.

Ive thought about adding water up front to smooth her out.

When you say neutral, is that with the cavitation plates being in parallel with the running surface or with the waterline?

I had a different drive but my experience was run the drives neutral no pos or neg trim. I used my tabs more than anything when on plane. I would try that n stead of tucking the drives to get rid of a porpoise. I would cruise 40 at 3800.

It's doesn't matter what the number is on your indicators as long as you know where level is. I think you might need a little cup put in your props to carry the bow better. What's happening is it's catching and lifting the bow and falling again. And will just keep going like you're on a trampoline. Are the props Plus or straight Mirage ? Also dropping some tab won't hurt while cruising.

They're Mirages. The concensus seems to that the 311 likes the Mirage and not the Mirage Plus. I wish I had a set to try. If I moved to a Mirage Plus, I'm thinking the right one to try would be a 25P. This could be a prop issue... I remember that our Cigarette Bullet porpoised a good deal running these props (they came with the boat). We went to a set of Bravo One 26P's and the boat loves it.

Dropping the tabs doesn't seem to help much, unless I really drop them.

I have everything marked. Again, what's considered level? Cavitation plates level with the running surface, or level with the water line/ running attitude? I'm thinking running surface... if that's the case I'm way off from running her at level (on the indicator).

level = propeller thrust in a straight line from running surface i.e. neutral trim

Straight edge on bottom of boat, set your drives till prop shaft is on same plane
Tabs: straight edge on bottom of hull sticking out under tab, measure distance front and rear to make equal. Notice how high tab is mounted on transom back edge make the same.
Don't be afraid to play with the tabs, do the equal/same time a stab at a time and give the boat time to react,
back edge 2" down at cruise is not a lot,

That's how I have her set up (I have thin red vinyl tape marking neutral), and I am never able to get even close without porpoise setting in.

I'll give it a try over her weekend.

Speaking of which... I need to plan some time where it's just me and the boat... no plans to meet anyone or hang out. Seems something's always going on. We've been using her a lot, and it's not even summer (this is a good thing), but I need some one-on-one time with her to explorer her settings and boundaries and such.

FYI... Going to cross-post this in the prop forum. I'll keep both threads updated.

Use the Tabs, Thats the reason they go down that far!

your original question asked if it was normal to run with negative trim and i answered yes, up to a certain rpm. You can over trim it till it porpoises then bury the tabs to tame it but it will scrub speed. Basically below 3k trim is slighty negative then goes positive more and more with rpm and speed. Not sure what other answer you are looking for?

At 3k RPM, the trim is negative. At 4k rpm the trim is still negative. If I try to move toward less negative, she starts to bounce.

At first, I thought this was normal because I was out in the 'Bay in some good rollers, porpoising, but still running 50-53-55 MPH at 35-3800. The porpoise seemed to fit the conditions, and I guess I just didn't know any better. Going on a run with some buddies onboard, their thoughts were she shouldn't be running like this for the conditions, and to back the trim off, which I did and she settled. Later, we measured everything because we wanted to figure the limits, and we were surprised that we were not able to gain anything close to positive trim at the RPM we were running.

So... running her back to the marina Sunday, I tried playing with the trim, and got a lot of porpoise in relatively smooth water. The drives were a tick and half off of fully tucked in... anything more than that, and I could just about get the whole boat out of the water due to the porpoise. During the run where Josh shot the video from the Chesapeake Bay Friends and Family event (included earlier), they could see my props coming out of the water... we weren't going that fast, and the water wasn't that rough. That was with the trim set at about neutral. I don't think that's normal, and I'd like to figure out why.

It seems weird that your neutral trim is around 6. Everyone i have seen is neutral around 3. Your speeds seem good, you spinning props out or in?

This video is right at 70gps, trimmed to about 7.5

this is in glassy water, probably around 2,

Maybe ya need to try some 4 blades..I have a set of 24 pitch hydromotive I ran on my 330hp 311. I'm trying to trade them for a set of 24 bravos, but with your bigger motors they might work great on your boat. I can only spin them too 4000 rpm.

My 311 with 502 Mags and Bravos with Mirages.
I always kept the nose light. Anything heavy was stored as far aft as possible.
Anything less than 40 mph, Drives "just up from full down" (like 1). Tabs at 4/5.

Glass water, 50+mph cruise, Drives 4, Tabs 4
Rough Chop 2'+, your choices are below 30mph or above 50mph. Above 50, use more tabs to keep boat level peak to peak, run drives close to neutral.
WOT - keep drives around 4, raise tabs as speed increases, when tabs are fully up, start bringing the drives up. Mirages will keep a good bite to around 7 on the drives, above that will lose a bit of speed and add rooster tail.
4900 rpm, 23 Mirages, 1.36 drives. 72 mph with <40 gallons of fuel and 2 or 3 people. Anytime it had over 75 gallons of fuel, in smooth water, it couldn't break suction on the outside hull chines and it hurt it a couple mph.

But once you START porpoising, you have to pull the drives in, or add tabs to kill it, then you can bump them back up some. You can be porpoise-free, and then 2 or 3 swells timed just right will START the porpoising.

If you put kids in the front bed, and tell them to brace their feet against the "ceiling", you can INTENTIONALLY porpoise for them. They love it. If the water wasn't rough, they would do it with no bracing, and float in the air as the nose comes down. You can exaggerate this a bit with the throttles... Wives don't care so much for that.

I will try and get to this later but there is no way you should be having this issue. I had the same exact set up and it was rock solid. My guess is you have a prop issue but I will read this more later. For now i have to get to work.

Run a late generation 302, which I understand to be quite similar to the 311 that came the next year. While I didn't have the extent of the porpoising problem you have, things got all kinds of better when switching to Bravo 4 blade props. Nose came down, sub WOT speeds increased, and over all just a better SOTP feel. Did lose a bit at WOT, but that was still a good trade for me. Run TRS like yours, so have to be careful of not overloading the props on hole shots, but shouldn't do that anyway; it ain't a ski boat.

How much HP do you have for your motors? Are they 420hp 502's or? If they are 420's then IMO you are spinning way to much prop. Try a 23 or 25 at most. 23 on mine was more user friendly for day to day but my 25's gave me a little more top end. Thing is to get that top end I really had to trim it out like crazy. I can not imagine any more pitch then that. Try a plus 23. Again this is assuming a 420hp motor or close to it.

The 502s are the 415 variety (415, 425, 430 depending on who you ask... regardless... more torque than a 420). I had 23 Mirages on her, and she'd peg the rev limiters. Best I could get out of her speedwise was 65-66. Again, she would bang the limiter way too early hence the move to the 27s that I had access to.

I did some testing this evening... results in the next post.

Took the boat out this evening and here are some observations... I took a voice recording after my testing, and for the most part, below are my findings.

Fully tucked in, the indicator is at the slash between 0 and 1.

Getting on plane is no issue.

Tests conducted at 3-3200 rpm.

If I run the trim up in large bursts, I get ridiculous porpoising. The boat will porpoise so bad that she'll begin to get the drives out of the water enough to unload the props.

Restarted the test...

If I slowly bump up the trim, I can alleviate the severe porpoise, but I mean it has to be a "tap tap" on the buttons. If I miss, she starts the cycle all over, and I have to tuck the drives in to get her under control. With this method I can get to neutral, but the steering becomes extremely vague. Steering inputs are delayed, and she feels loose. Looking out the back, she's throwing a steady prop stream with a near parallel pattern out about 100 feet behind the boat.

Neutral is at the slash between 4 and 5.

I can get beyond the neutral point, but I have to tap the trim incrementally, and increase the throttle. I took her to about 4200 with this method but ran out of room.

I think two things are hurting me.... nose cones and props.

Thoughts?

At 3200 if you trim the boat too much it will ALWAYS porpoise. There isn't enough power to carry the nose. There is no need to trim it that much as those rpm. When I'm at those rpms I hardly ever will get the trim past 1-2... I use more input with the tabs.

I think your your indicators are wrong. It should not throw a rooster tail at neutral trim. Almost scientifically impossible actually cause the prop shaft is neutrality inline with the bottom of the boat which actually is still at a downward angle cause of the way the boat runs in the water. If it is feeling loose that means the boat is starting to lift, but it shows Ike feel really lose at 3200rpm. Not going fast enough to get these heavy pigs out of the water at 40-50mph..my boat actually has a slight twitchy feeling at these speeds and any steering input is very noticeable.

Nose cones should not cause a porpoise.

I just got back in from looking it over again. Using a straight edge, the drives are level/neutral at 4-5 on the indicators. We looked it over THREE TIMES. All three times, same results.

To clarify... I never said the boat was throwing a rooster tail. The propeller stream was in the water (as you would expect to see behind the boat while running). I have never produced a rooster tail with this boat even with the trim up at the edge of the indicators.

I agree on the twitchy feeling. That's exactly what I'm experiencing. On another front, I found that the steering is very loose at the transom assembly. We held the tillers and tested movement; the drives are tight, and the play is at the actuator. I'll need to get in there and investigate/fix.

I'll post more later... I'm late leaving the office for an appointment.

Tom, Quick question was the condition this bad when you had the 23's? You will NEVER see a rooster tail with a 311 and TRS drives. If you do make it go away because you are about to blow your drive. ;-) I am almost positive you have a set of props that do not agree with your boat. The fastest props I had for my 311 were 25 mirage pluses that were labbed by BBlades. They got me to 72mph best speed and 70 all the time on GPS. That is about the best you will see with one of these boats. I may still have them and could work something out with you if you want to try them or even buy them. They won't work on my 353. have you tried a WOT run yet to see what it will do? It must be so slow out of the hole with the 27's. I know going from the 23's to the 25's was a huge difference on my boat as far as speed out of the hole.

I'm definitely interested in the props... if you could shoot me a PM with details, I'm sure we can work something! Thanks!

I've never seen a rooster tail with this boat. Best I've had her to speeswise is 69.8 on GPS... this was in a light chop out in the Currituck Sound (NC). She doesn't seem too slow out of the hole; I'll time her next time, but she gets right up fairly well and is comparable to the Cig Bullet when it had the same props. I'm sure the torque of the 502s is helping a great deal. The 23s planed a little quicker, but not by much. I only ran them a couple of times before I swapped... the boat porpoised similarly.

Your old props were 23 mirages? So odd. Would be interesting to see if maybe you have more rocker then most in your hull. If you put your strait edge on the bottom of the boat is it flat or is there rocker or hook? Also just grasping at straws but turning props in or out and have you checked your drive alignment? Just for reference my boat was a 98 with 420hp 454's so we should be almost the same numbers and performance. I am on my way out door so have to run but did you say you had nose cones on there? I had my boat with and with out nose cones and I felt it was better with out them. I believe I was turning in but will have to try and make sure of that for you.

If you know someone with a set of bravo 1 4 blades I would suggest trying those for sure. You will love the difference the 4 blades make. Also are your props spinning in or out? mine porpoised pretty bad when i bought it. the props were spinning in. since the switch to spinning out, the boat is much more stable, and rides so much better. I can trim up with no porpoise until about 4-5 at 3200 rpm.

I'll break out the straightedge to check it out. How far forward should I be looking? There is no hook in the hull; I've already check that. She's perfectly flat for the first three feet.

The props are turning out.

I have not checked alignment (I mentioned in another thread that I would), but I've gotten information from all over the place about what it should be. They are set very much toe-in at this point (by my eye), but the prop streams seem to be where they're supposed to be; I'll check this weekend. If I'm reading right, I should be slightly toe-out (1/8 to 1/4 inch) on the bullet compared to the prop shaft. I read something where Formula changed their set up to dead even/parallel, but I only read that in one place.