Zipwake trim tabs or Jack plate

[David Anderson]

Since changing my batteries from AGM's to Lithium's and lost 150#'s my Ranger 620FS with a 250HO G2 seems to porpoise a lot more at cruising speeds(30 - 40 MPH). The motor is mounted as high as it can go, I run an RX4 x 20 pitch, and I have to trim in the motor in more than before to settle it down. Not that this is a huge problem but when trimmed down my gas mileage drops by 15% or more. Sometimes with the wrong load I cannot stop it without increasing the speed to over 40. It feels like my motor is now mounted too high and thinking that either Zipwake trim tabs or a hydraulic Jack plate would help the situation. I suspect the jack plate would give me more options when fishing more guys or bigger water. Any thoughts as I have never run a jack plate before but understand the concept of both. Thanks

[Waxy]

Originally Posted by David Anderson

Since changing my batteries from AGM's to Lithium's and lost 150#'s my Ranger 620FS with a 250HO G2 seems to porpoise a lot more at cruising speeds(30 - 40 MPH). The motor is mounted as high as it can go, I run an RX4 x 20 pitch, and I have to trim in the motor in more than before to settle it down. Not that this is a huge problem but when trimmed down my gas mileage drops by 15% or more. Sometimes with the wrong load I cannot stop it without increasing the speed to over 40. It feels like my motor is now mounted too high and thinking that either Zipwake trim tabs or a hydraulic Jack plate would help the situation. I suspect the jack plate would give me more options when fishing more guys or bigger water. Any thoughts as I have never run a jack plate before but understand the concept of both. Thanks

Both will likely solve your problem.

The trim tabs/zip wakes will help control your porpoise, but they work the same as trimming in, they push the bow down. The result will be the same, you’ll lose fuel economy by creating more drag. Trim tabs are an awesome upgrade, but in my opinion, they aren’t the best way to go about fixing a porpoise.

The jack plate will let you adjust the height to eliminate the porpoise, AND, maintain maximum fuel efficiency. I use the jackplate on my Warrior for exactly this purpose every time I’m on the water. The best height for top speed is NOT the best height for cruising or rough water. With the jackplate, it’s always optimized with the quick push of a button. It’s a major upgrade.

Waxy

[hempbake1]

Sounds like you need to correct a prop/ motor height issue first. Motor height will affect how you carry the bow. try having someone sit on the bow step and see how it rides. If it helps then your prop is trying to raise your bow too high. hence the porpoise. Thats the cheapest route of diagnosis. Lower your motor 1 hole and see what happens. If it's running to high now it will lose bite and porpoise. You may not need anything like a jackplate, but they are nice for complete and accurate adjustments based on weight and conditions. Don't try and correct a porpoise issue with zipwakes, thats not what they are for. Also if it's not a Pro series ranger you cant add zipwakes. transom is not flat enough for mounting.

[bbheli]

Originally Posted by David Anderson

Since changing my batteries from AGM's to Lithium's and lost 150#'s my Ranger 620FS with a 250HO G2 seems to porpoise a lot more at cruising speeds(30 - 40 MPH). The motor is mounted as high as it can go, I run an RX4 x 20 pitch, and I have to trim in the motor in more than before to settle it down. Not that this is a huge problem but when trimmed down my gas mileage drops by 15% or more. Sometimes with the wrong load I cannot stop it without increasing the speed to over 40. It feels like my motor is now mounted too high and thinking that either Zipwake trim tabs or a hydraulic Jack plate would help the situation. I suspect the jack plate would give me more options when fishing more guys or bigger water. Any thoughts as I have never run a jack plate before but understand the concept of both. Thanks

Trim tabs will give you more options. Jack plates are great for efficiency and to move the motor away from the boat for less turbulent water and to allow you into even shallower water. If the centerline of the prop is even with the bottom of the keel line you wont gain anything going higher except for skinny water. Also motor to high will result in the prop letting go in turns and lack of bow lift. Sometimes porpoising is caused by too much bow lift and dropping the motor will give it more bite and make it worse.

In a 20' boat weight and center of lift is an issue. Trim tabs will solve it and will also level the boat based on the load positioning. Past that active trim if your not great at trimming the motor will give you optimal RPM's

[REW]

All of the above.

[Waxy]

Originally Posted by bbheli

Trim tabs will give you more options. Jack plates are great for efficiency and to move the motor away from the boat for less turbulent water and to allow you into even shallower water. If the centerline of the prop is even with the bottom of the keel line you wont gain anything going higher except for skinny water. Also motor to high will result in the prop letting go in turns and lack of bow lift. Sometimes porpoising is caused by too much bow lift and dropping the motor will give it more bite and make it worse.

In a 20' boat weight and center of lift is an issue. Trim tabs will solve it and will also level the boat based on the load positioning. Past that active trim if your not great at trimming the motor will give you optimal RPM's

Mounting outboard too high is just a bad, actually probably worse, than mounting it too low, due to the potential for a loss of control. That's why most OEMs/dealers error on the side of lower when mounting the outboard.

Porpoising is due to there not being consistent thrust for the given speed and trim angle to hold the bow up. As the prop goes back and forth between grip and cavitation, it causes the bow to be lifted and dropped repeatedly. In really bad cases, it becomes harmonic and can cause severe bouncing.

The simplest solution to prevent a porpoise is to just eliminate trim angle to zero, or even negative trim, and eliminate bow lift. The problem is, that's pretty inefficient. The jackplate allows you to tune a third variable in order to find the ideal mix of grip and bow lift, and will allow you to use some positive trim angle in order to increase efficiency. In my experience, motor height changes as small as 1/2" can have a significant impact on handling and performance. It can be the difference between efficiently cruising with or without a porpoise. The key is the ability to adjust all of the variables to find the most efficient setting that balances thrust and lift.

I'm a HUGE fan of trim tabs, I'd never want to own a boat without them. They will solve the porpoise, but so will just trimming the outboard all the way in. You're doing the same thing with trim, and it's free. I do think that a lot times, a porpoise is created by using too much positive trim for the given speed because we all want to "get the bow up", when in reality, the boat would run better and more efficiently with less trim and a lower bow.

Waxy

[Scooter112]

I am not sure that zip wakes are able to be put on your boat as you listed it only as an FS and not the FS Pro. The FS Pro is the only model I am aware of that can have zip wakes added because of a change they made to the hull.

I have a 621 with a jack plate and love having it now that I understand how to use it. You raise the motor all the way up for take off and as you come up on plane lower the jack plate and trim up the motor. This creates bow lift and gets the boat out of the water when calm for efficiency and good mileage. When rough you find a mid point that allows you to keep the prop gripping the water and control the bow height depending on what the waves are alike.

The other big advantage of the jack plate is you can raise the motor when loading and keep it trimmed down without worry about hitting bottom.

If I were you I would first play with the motor height and drop it a hole to see how the performance changes before spending the money unless you want a jack plate.

[SLE]

Originally Posted by Scooter112

............. You raise the motor all the way up for take off and as you come up on plane lower the jack plate and trim up the motor. This creates bow lift and gets the boat out of the water when calm for efficiency and good mileage........

Your backward here buddy. For best hole shot, you trim the engine down as far as it will go, lower the engine with the jackplate, and then once out of the hole and up on plane you begin jacking the plate up (raising the engine) and trimming the motor up. When you know your boat well and where it runs best, you can trim and run the jackplate up at the same time to the optimal positions and then tweak each slightly a tick at a time to get the most out of the boat.

Back to OP, either will solve your problem but I'll second that there's a good chance you won't be able to use zip wakes unless your have the 620 FS Pro hull that has the notched out areas for the interceptors. You maybe able to run a more traditional tab such as a Bennit or Powertran if you choose this route.

A combination of jack plate and prop will also likely solve your issue, with the engine mounted in the highest position, you may have your issue right there. Just lowering your engine one or two bolt holes may remedy your proposing problem. A jackplate will give you the flexibility to raise or lower on demand depending on water conditions and the specific prop your running to get your motor at the optimal height. I feel like this is the proper solution and while trim tabs would also solve it, your really covering up the issue with them and not actually fixing it. I have a Bobs extreme jack plate and zip wakes and find them equally valuable but for different reasons.

[SLE]

I will note on the holeshot discussion that I don't need to run my plate all the way down, but somewhere between 2-3" up on the plate yields the best results while I'm between 4" and 5" up on the plate for the best top speed. So I truly don't use the bottom 2" or the top 1" unless I'm at the dock in skinny water or on shore wiping the engine off and trying to reach the top of the cowl, lol. so with 6" of true adjustment, I only use 3" of actual adjustment for optimizing how the boat runs on the water.