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Posts: 205
| Bought a new 18' Deluxe Jon since I do a lot of river fishing. Boat is 1860 Jon with rod boxes, live well etc. In the stern I have 9 gal fuel tank, one battery and Power Pole on Transom. Dual batteries have been move forward. No addtional weight distribution is feasible. Boat is powered by 50 HP Merc Tiller.
Boat porposes at 21 mph when I am alone and at 23 mph with one passenger I installed a no drill whale tail device which corrected problem but I can't stand it and don't want to be fighting it with trolling motor in current or weeds. Haven't talked to dealer yet but here is my initial plan.
Remove whale tail
Install manual jack plate to get 4 inch set back and raise motor on transom. Add negative transom wedges to get more angle on transom
Thoughts??
Thanks |
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Location: 31 | If those are your only issues with the whale tail, what about just tilting the motor out of the water as needed… a tilt/trim switch in the front would be helpful to tilt just enough of the whale tail out of the water so you still have a rudder. |
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Posts: 1089
Location: Hayward, WI | A set of Smart Tabs might help. Or I have seen people weld on tabs on the back of the boat to act like trim tabs. |
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Posts: 1209
| Lowering the motor will help. Raising will not. Less trim angle. |
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Posts: 32886
Location: Rhinelander, Wisconsin | Trim tabs, 6" manuals if you can find a set. |
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Posts: 205
| Unfortunately the boat has a welded transducer mounting plate right where a Smart tab would go on the starboard side. That would have been a great fix. Dealer says put on the jackplate to get the 4" setback. |
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Posts: 20219
Location: oswego, il | I have a whale tail on my little princecraft and fish rivers with it. Not been an issue with the trolling motor. |
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Posts: 6
| pstrombe - 10/25/2019 9:05 AM
I installed a no drill whale tail device
Where did you find this? I'd like to see if my porpoising
issue might be helped with a fin, but I just can't bring myself
to drill into my shiny new motor.
Sorry, I have no advice for you. |
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Location: 31 | pstrombe - 10/25/2019 9:05 AM
I installed a no drill whale tail device which corrected problem but I can't stand it and don't want to be fighting it with trolling motor in current or weeds.
Thoughts??
Thanks
Not following the reason for wanting to remove the whale tail after it fixed the proposing problem if your only issue with the tail is when casting. Why not just tilt the motor out of the water a little when casting? |
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Posts: 3480
Location: Elk River, Minnesota | Hiya,
Assuming this is a crestliner deluxe jon boat?
When loaded just by yourself, do you have an idea of the rpms you are getting out of the motor at full throttle?
If you are over propped, the motor is not turning enough rpms to hold the bow up, thus the bow rises and falls. If you can try a prop with 2" less pitch, and potentially even a 4 blade prop, you should be able to get the porpoising to stop altogether without the need of a whaletail or a setback. The setback plate would allow you to raise the motor out of the water more, which will give you some RPM's (my gut instinct says this is what you are needing) and will make the center of gravity move back a little, thus making the boat trim more with less trim used.
Depending on where they mounted the motor on the boat (assuming they drilled and bolted), you might be able to move the motor up as well, but there is always a trade off... Moving the motor up gains speed, but increases slip, so the boat will not be as responsive in corners. If you do this with an aluminum prop that has no cupping, you'd be hard pressed to get things working.
Before anything, I'd consider a prop with lower pitch in the same diameter you have and see how the boat performs. If it's new, you should be able to go back to the dealer for the prop. Heck...if I had a prop that would fit your motor and you are in the twin cities area, I'd let you borrow to try...
Steve
Edited by VMS 10/28/2019 7:15 AM
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Posts: 205
| I put a tiny tach on last week and although I was on the water this past week I had three big guys in the boat and wasn't able to really test the boat performance with my normal load. I should have mentioned I am running a 4 blade prop and anticipate taking the boat to Florida in February. I enjoy the shallow water bite around Matlacha and will probably go with the jackplate. Had one on my previous boat and found the additional motor height provided with the offset helpful. I'll know more this weekend as I will be out on Lake Pepin.
Thanks |
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Posts: 3480
Location: Elk River, Minnesota | Hiya,
Any updates?
Thanks!! |
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Posts: 205
| Ran the boat for a couple hours this weekend with normal load. Porposing is minimal and only occurs in light chop. It appears my Tiny Tack is right and I am pulling 4800 rpm at full throttle while doing 23 to 24 mph on my GPS.
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Cavitation plate is approx 2 inches below hull. I'm probably going to do the jackplate. Get the motor back and up slightly before I look at the prop issue.
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Thoughts? |
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Posts: 3480
Location: Elk River, Minnesota | Hiya,
Definitely low on RPM which will be the main issue.
If the plate is that low, it can easily come up close to 3 inches which would get you roughly 300 rpm give or take a few. No doubt it is too low.
If you go jackplate, you'd probably be able to come up a touch higher as well as putting the motor back a few inches will put the prop in cleaner water, and since the water fills the hole the boat made passing over, it can naturally be higher out of the water.
Guessing this is a 50hp 4 stroke, which if my research is correct, max rpm is 6000, so even with a jackplate, I have a feeling you would still be low by about 400 rpms, or roughly 2 inches in pitch.
Steve |
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Posts: 205
| Roger That ..... Thanks |
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Location: Athens, Ohio | I put a fin on my 225 outboard and it helped a lot with getting both on and off plane. m |
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Posts: 205
| Update:
Installed a Vance Manual Jack Plate last week and was able to get out on the river today.
Jack plate gave me 4" of backset
Raised engine over 2" - cavitation plate is now even with humm bottom
I'm running a 4 blade aluminum prop M10.1x14P (I assume the 14 is the pitch)
Motor is labeled for a 12x22 - 1.83:1
Difference was immediately noticeable
Great hole shot
I was alone in the boat and the porposing started at 25 mph - conditions were bad with chop running with current and strong winds
Never was able to completely open up the throttle but I did reach 34 mph with throttle left
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I suspect that boat would run pretty well with a passenger if they sat up front.
I would like to take this one step further
What are the options
Reprop? ( not sure if dealer gave me the best choice in props)
Lower motor
Install transom shims
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I'm thinking of slipping in a pair of transom shims
I would appreciate your thoughts ...... Thanks
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Posts: 3480
Location: Elk River, Minnesota | Hiya,
I'd switch props....I would check out Solas Amita series which will be cupped throughout the blade, but I'm guessing you still need to go down in pitch. The amita series will be cast differently than stock props (squeeze cast which will flex less and thus can be ground thinner which will allow the prop to "bite" better. You can also have your prop tweeked by adding cup to the tips of the blades which will help hold the bow up. The trade-off, though is it will lower your rpms. From your previous information, I suspect you are still needing higher RPM to hold the bow up. What were your rpm's when you had the boat up to 34mph?
The only other thing i can think of is to check the pin on the transom bracket to see if it is in its most tucked in position. If it is out a hole or two, that could be part of the issue as well....but...if you are unable to trim up at all, I believe you will be low on RPM's yet. Get that motor up to the 6000 rpms when you are alone with your normal load and full tank of gas, and you will be golden.
Steve
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Posts: 205
| I think you're right. Motor is tucked all the way down. I calculated out the exact boat weight, power pole, batteries, trolling motor fuel, gear, guys etc. and ran the Merc and Solas prop calculator both indicate I should be running a 12 not a 14.
Whats been the overall opinion on the solas props.
Thanks
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Posts: 3480
Location: Elk River, Minnesota | Hiya,
I used the Solas Alcup 3 back when they made that prop on a Johnson 50hp 2 stroke. It is the same design as the amita series I believe, and I had really good luck with it. Ran more like steel at the price of aluminum.
I feel you would be very happy with that prop.
Steve
Edited by VMS 11/25/2019 8:55 PM
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Posts: 1716
Location: Mt. Zion, IL | i know i am talking apples to oranges, but on my evinrude 50 etec on a 17' aluminum deep v tiller, 4 blade 19 pitch (much different gear ratio from Evinrude to Merc, but recently switched to a 4 blade from a 3 blade for the same reasons you mention. I set the height 1st correctly by running the boat. This is really the only way to dial in the correct height. The anti-ventilation plate should ride just on top of the water when running. You can find several pictures online of the merc performance boats with 5 or 6 400R motors and all the plates are just above the water level, even for ocean setups.
basically i switched from a 3 blade ss (evinrude viper) to a 4 blade ss (evinrude rogue) due to so much stern weight. Evinrude's catalog calls out this specific prop for high stern weight boats and advertises faster speeds and time to plane. While i don't feel it offers any advantage in time to plane, it is significantly faster. I could only trim up about two touches of the button by myself vs about 10-12 degrees with dad in the front of the boat with the 3 blade mounted. The 4 blade prop lifts the stern and i can actually trim the boat up more with the 4 blade, even with 2 more guys in the boat.
If you are just even with the bottom of the boat, i would look at going up at least an inch, possibly 2 more if possible. You may have to mount the motor to the jack plate by using a lower set of holes.
3 blade by myself - 30.2 mph 5640 rpm
3 blade with 2 people - 33.4 mph 5850 rpm
4 blade by myself - 38.4 mph 5730 rpm
4 blade with 2 people - 35.7 mph 5620 rpm |
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Posts: 3480
Location: Elk River, Minnesota | Hiya,
The only issue I think he is gong to run into is the selection of steel props for his motor is very very limited, so he may very well be needing to stay with aluminum. If that is the case, he can maybe bring the motor up an inch, but anything more is not going to hold. A good steel prop would do wonders for bite and allowing the motor to come up higher, but I think he's a touch limited.
Steve |
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Posts: 205
| Thanks guys
Ill be headed to FL for a couple weeks in Feb. so I will be able to try some tuning before ice out up here. I didn't think the 4" offset would allow me to raise the motor more than 1/2 inch or so. Is there a rule of thumb that suggests motor height vs. setback? I have a Merc Spitfire on the boat now and anticipate moving to a 12 pitch just not sure what out there besides a another Spitfire. Looked briefly at Solas but I need to go through their website again. |
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Posts: 3480
Location: Elk River, Minnesota | Hiya,
There's no real rule for setback as every boat is different, but you are able to raise the motor up higher than the given bolt holes. It's a testing situation more than anything. Keep moving the motor up until you lose handling on moderate turns. Be prepared to trim down in corners as that is a good thing for carving a nice turn. If you are too high or trimmed out, the prop will blow out and let loose.
One thing to be careful of though, when you go past the normal bolt holes....
With a setback or jackplate, you can potentially raise the motor high enough that you lose water pressure to your cooling system and that would be a bad thing. If you have a pressure gauge, you can monitor what is happening. I'm thinking you could try setting your anti-ventilation plate 2" above the lowest point on the boat as a start. Solas should have a steel line as well. I think michigan propeller might have something as well. I'll do a little searching to see what I can find as well.
Steve |
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Posts: 205
| Looks like a Solas 1313-108-12 is their recommended stainless steel prop to replace the Spitfire 4 blade 12 pitch. |
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Posts: 205
| Hi Gents
I was able to put about 20 hours on the boat while I was in Florida. Be myself it performed well but still wanted to porpoise above 25 mph. I had a real mix of passengers while on vacation. Some mornings it was the gals and some mornings it was the guys. Boat performed much better but was sluggish out of the hole and trimmed poorly when I had the three large mammals on board and am confident that tucking the motor under just a bit more will solve it. I just installed a pair of transom wedges and am calling it done. In total I have added the jackplate, prop and transom shims. Now I just need to get the height right. River is open so once I finish some trolling motor and seat changes I will give her a whirl. |
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Posts: 1247
Location: Walker, MN | I might be too late on this, but transom wedges seem to be a cheap option. They get rid of porpoising by giving you 5 degrees or so of negative tuck. They seem to be utilized a lot for building ride performance into saltwater skiffs. https://thmarinesupplies.com/products/reverse-transom-wedge |
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Posts: 205
| It would have saved me a lot of time if I had just started with the transom wedges. The bottom line is that these big jons (at least crestliner) does not have enough negative angle on the transom. |
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Posts: 3480
Location: Elk River, Minnesota | Hiya,
What were your rpms in Florida when you fished by yourself with your normal gear?
Did you move the motor up any higher than the plate level with the transom? Chances are you can come up a touch more as the motor is further back.
Steve |
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Posts: 205
| Actually had the boat out yesterday on the river. Launches are open and the only restriction is too keep your distance from others. Boat came on plane quick and I had enough reverse transom angle I could trim up a little while on plane. Porpoising is gone. Rigs not a fast as I thought it would be. 30 mph but it handles nicely. I was running just under 5600 RPM wide open motor sounded great but I'm not sure I can trust the little Tach. I did not cavitate on moderate turns so I am going to bring the motor up an inch and see how it handles. Also had a chance to try the Ulterra. I can see I am really going to like it. Also got to run the side scan and observed clusters of fish congregated just out of current - carp I suspect. Probably going out again on Monday but will take a couple rods along |
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