G21 porpoising

[stud303]

2015 G21 550. We bought it last fall and love the boat but we are having a problem with it porpoising at cruise speed.
Anything over 20 mph the bow starts to rise and fall and get worse until you pull out of the throttle and then get back in it slowly.
I have filled the bow up to 100% and emptied the rear and this somewhat cures it but Im curious to see if this is a common thing on G21's
If all ballast is empty and I have over 4 people I cannot drive over 20 mph without it starting to porpoise so bad I have to slow down.
I have it on "back to dock" and ncrs on "low" sensitivity.
This seems crazy for a 100K boat.

[ScooterMcgavin]

This isn’t common at all from my experience, maybe something going on with your zero off. I would get it looked at by dealer or mechanic.

[nyryan2001]

2015 G21 550. We bought it last fall and love the boat but we are having a problem with it porpoising at cruise speed.
Anything over 20 mph the bow starts to rise and fall and get worse until you pull out of the throttle and then get back in it slowly.
I have filled the bow up to 100% and emptied the rear and this somewhat cures it but Im curious to see if this is a common thing on G21's
If all ballast is empty and I have over 4 people I cannot drive over 20 mph without it starting to porpoise so bad I have to slow down.
I have it on "back to dock" and ncrs on "low" sensitivity.
This seems crazy for a 100K boat.

What is your NCRS at? It should be at 0 when cruising. Can you take a video?

[xxrb2010]

Try NCRS at off when cruising,

Strange behavior for sure, I have a 2016 with the H5 or something like that and the boat is flat as it can be when crusing over 25 or close to 30.

[tchancey]

I have a 2016 with the 550...also in Denver so it's a pretty good comparison. This is my first summer with it, but I haven't noticed that problem. The closest I can say I've come to that was pulling a beginner wakeboarder at 17 MPH with all passengers in the back of the boat. I wouldn't call it porpoising, but the bow would slowly rise & fall as it would lose a little speed then gain it back. I could affect it quite a bit with NCRS settings & probably can eliminate it entirely with a little more experience with the boat.

I'll do some more testing next time out (a little faster) and maybe I can duplicate, then cure it.

Are you running the 17" Acme 2561 prop?

[Kenv]

Guys....your NCRS for cruising should be set to "AUTO"......make sure the green ring lights around the soft key to show it's ON. I've got the 409 in my 15 and have never porpoised. May be something with the 550...but I doubt it....

[stud303]

I have the 2261 prop (15x 14.25). They didn't use the 17" prop until 2016.
I use the auto setting on the ncrs with back to dock. I have tried the high and low sensitivity and also turning it off. No change.
Not sure if it is the zero off, not sure how that works. I do know it doesn't bounce off a cruise control and rev up and down.

As soon as you hit about 20+ mph the front starts to rise and fall and it gets worse and worse until you pull the throttle back. It will get so bad that 1) I won't let my wife drive the boat 2) It is just plain scary if your in the front seat (4' + rise and fall).

I have owned $800 boats and $80,000 boats. This is the worst I have ever seen.
Could it be the ncrs plate is deploying and retracting trying to catch up with leveling the boat off? Something wrong with the computer?

[Cpan13]

I’d definitely check with your dealer. I’ve got a 2014 G21 with the 550 and never had it porpoise like that. NCRS might not be working.

[xxrb2010]

Guys....your NCRS for cruising should be set to "AUTO"......make sure the green ring lights around the soft key to show it's ON. I've got the 409 in my 15 and have never porpoised. May be something with the 550...but I doubt it....

Interresting,

I re read the manual on page 22/23 for my version (2016 Nautique Owner's Manual - LINC 3.0 (G-Series Boats)) and as my speed control is off when I cruise, according to the manual most of the NCRS actions are also off.

So in my case no NCRS when cruising. Will check the green lights around the soft key next time I play with speed control on/off.

[Kenv]

Yeah....try auto for sure. Sometimes I turn it off/on just to make sure it reads it. It will pull the bow down nice for the cruise. Also....my speed control is off when I'm cruising and I still have access to NCRS Auto mode.

[nyryan2001]

I have the 2261 prop (15x 14.25). They didn't use the 17" prop until 2016.
I use the auto setting on the ncrs with back to dock. I have tried the high and low sensitivity and also turning it off. No change.
Not sure if it is the zero off, not sure how that works. I do know it doesn't bounce off a cruise control and rev up and down.

As soon as you hit about 20+ mph the front starts to rise and fall and it gets worse and worse until you pull the throttle back. It will get so bad that 1) I won't let my wife drive the boat 2) It is just plain scary if your in the front seat (4' + rise and fall).

I have owned $800 boats and $80,000 boats. This is the worst I have ever seen.
Could it be the ncrs plate is deploying and retracting trying to catch up with leveling the boat off? Something wrong with the computer?

Run at speed with your NCRS set to ZERO/0. Post up a video showing you running at speed and NCRS at 0.

[wakerider107]

Many wake boats porpoise. MC's would do it if their attitude adjustment plate isnt at 50%. Same with Supra/Moomba.
Something isn't right with your NCRS and it's most likely just not on the right setting. Worst case you have a bad actuator.

[NautiqueJeff]

I agree that something isn't right. Either the weight in your boat is substantially too far back, or there is an issue with your NCRS.

Ryan is right that NCRS at zero is the best for cruising. I didn't believe him when he first started posting about that last year, but I tried it and I agree that it gives the best ride and fuel economy. I always keep NCRS at zero now unless I am pulling a rider.

Even so, any NCRS setting should allow you to cruise without porpoising.

[nyryan2001]

NCRS 0 is the most mellow for wake sports. Smallest wave, bow down, most efficient prop shaft angle. Fastest WOT boat speed here.

NCRS 5 creates the biggest wave for wake sports. Bow high. Most inefficient prop shaft angle. Requires 300-400 more RPM to run NCRS 5 as compared to 0 for the exact same activity which is why there’s an auto NCRS. To not deploy NCRS 5 on launch unnecessarily dragging a huge trough when it’s not needed till 11mph+ for surfing or 23mph for wakeboarding. And also to keep the bow down for good visibility during a launch.... and a faster more efficient (shaft angle) launch.

need to know if the boat is stable at NCRS 0 at speed. Then, is there a difference between NCRS 0 and 5 at speed? Should be at least 1ft of bow rise going to NCRS 5. If not you may have a bad actuator on your NCRS.

[tchancey]

I did some testing this weekend with your question in mind. We had 6 people in the boat (mostly light'ish teenagers). Sometimes they were all sitting in the back, and sometimes mostly in the bow.

I tried everything to recreate your issue. Turned NCRS off for a while & ran in the 20's. No porpoising. I also tried high & low with various settings. Never did I experience the issue you do. I mentioned the prop before because it's the only difference I can think of between our boats. I have a 2016 but I think all else is the same (even our engines & altitude are the same).

Good luck with the troubleshooting. If there's anything more specific you'd like me to try let me know.