Crestliner VT18 - Performance tabs (wedges)??

[ReefOctopus]

Good morning all,

I have a 2017 Crestliner VT18 w/ 115 ProXs. The Motor has approx. 7-8 Hours on it at this point and I have hit a top speed of 45 GPS (alone). With 2 people I am right around 40-41 mph.

My question is.... If I trim up the boat wants to go faster but it begins to porpoise like a demon. The motor is the 2nd hole on the transom.

Will performance tabs help this? The dealer thinks so.

Does anyone have any thoughts? Is there any negative to the tabs being added to the bottom of the boat? (NOT TRIM TABS)

[fishon396]

You might try moving to the third mounting hole. Seems like similar aluminum boats like that set up.

[GeauxTide]

What is your WOT RPM? What prop, pitch? Most semi-vee manufacturers put wedges (tabs) on them for that purpose. I also recommend 3rd hole.

[ReefOctopus]

My tach is reading 5,200 (could be inaccurate....) I honestly have no idea what prop is on the motor, stock aluminum.

[njpaulc]

Before wedges get a stainless prop and move the engine up. Most tin boats don't require a lot of trim.

[ReefOctopus]

Before wedges get a stainless prop and move the engine up. Most tin boats don't require a lot of trim.

That makes sense. What prop does everyone recommend for this setup?

[GeauxTide]

I'm running a Laser2 20" and a Spitfire X7 19". These will work if your motor is not a Command Thrust. 5200 is 900rpm off the limit, so you need a lower pitch prop. A 1 inch change in pitch gives 200rpm. One other thing - you're still in break in. Make changes after that.

[ReefOctopus]

I'm running a Laser2 20" and a Spitfire X7 19". These will work if your motor is not a Command Thrust. 5200 is 900rpm off the limit, so you need a lower pitch prop. A 1 inch change in pitch gives 200rpm. One other thing - you're still in break in. Make changes after that.

Should I wait to move the motor up 1 hole? Wait for prop as well?

[fishon396]

It took me some time to figure out my rt178 75hp fishing mostly smaller lakes and some trolling motor lakes. I finally figured out I was over trimming the motor mine needs 1/2 or less at top speeds so that helped with the porpoising. Then I bought a Mercury stainless 4 blade X7 prop and that helped more. Then with the help of forum members I figured out how to find the neutral trim position and that helped with torque steer, after those changes the boat is much more enjoyable to drive. And I am still learning.

[Casslaw]

I would move the motor up one hole as well and then I would call PowerTech Props. The people there are very knowledgeable and usually pick the right prop after one conversation. If you don’t like the prop they will exchange it for $35. I put the NRS 3 on my boat and it planes faster, corners SO much better, and I got more usable trim...still need to move my motor up though.

Good Luck!

[PolarKraft195]

Should I wait to move the motor up 1 hole? Wait for prop as well?

Absolutely! You need to get correct motor height & correct size SS prop before doing anything else. You'll probably not have to do anything else after that is done.

[Panama]

You will get a lot of opinions on what to do or try. I agree with getting the RPMs up, a stainless prop, and maybe raising the motor to see if it helps. The basic hull you have is very very similar to the RT188 or the Triton. They are almost identical to yours. There is a reason for this regarding the guy that designed the boat. They are almost identical.

You should be able to trim the motor out all the way at WOT or almost all the way ---- when it is right. I can trim mine out all the way at 6K without a porpoise on pretty flat water. I have video of that on this forum. The last 50-75% or so of the trim the bow raises and it steadily picks up RPMs and speed. You can actually feel in your seat when the boat lifts somewhat toward the end. I could not do this before the little trim tabs were added. When you get through experimenting, you might still have to put on trim tabs. They are no big deal. On the RT, they are simply a couple of small pieces of aluminum about 3/8 inch and about 2-3 inches long that are attached to the bottom near the stern. There are pictures on this forum. They make a world of difference. Some people with another brand boat have added a bead of JB weld along the bottom stern that basically does the same thing. It also helps with turning a hard turn at speed and not have the slide. I had mine put out more toward the edge a bit on each side - moreso than they come from the factory. I am happy with them and very happy with the boat.

This is just what I have found and my opinion. Others may differ. That's OK by me. I have had this boat 5 years this month and I experimented with a lot of different props and stuff when I first got it. Nobody knew what to run and I tried eight props I think. Mine is a Yamaha but I think the hull should act about the same. Good luck with your effort. Sooner or later you get to the point that you say... That's good enough for me and concentrate on catching fish more. I hardly ever run it WOT anyway.

[alanhore]

I have a vt17 and added tabs from Crestliner to my boat. It made a pretty big difference on my hull. I have also talked to other Crestliner owners that did not have as good of results with the tabs. I would start by raising your motor one hole. You are too deep now. After you raise your motor you should gain some rpms. these should help with the porpoise issues. After all is said and done a SS prop should be selected that fits your needs. Hard to beat a Mercury Spitfire X7 in a 19pitch on these hulls. It may not be the fastest, but is usually the best all around prop on many tin hulls.

[TritonTRXV8]

That makes sense. What prop does everyone recommend for this setup?

Im running a cupped laser prop myself. Alot lf folks like the x7 as well. Definitely try a ss prop and engine hieght first. Aluminum props in general do not perform well and can give performance issues yoy describe.

[ReefOctopus]

Wow, lots of good info. Thanks for all the replies. I will raise the motor one hole this winter and try out a new prop. It seems the general consensus is the Spitfire X7 19P. Does that sound about right?

[GeauxTide]

Poifeckt! Crestliner should give you the tabs. Very surprised they weren't factory installed. They should cover the welding under warranty, too.

[tjsellsfords]

Mine came with the tabs on it. Surprised yours doesn't have them. I went to the 4th hole and haven't changed my prop yet, but I can now get 46-47 without porpoising. I expect I can get a couple mph better with a different prop. Not in any hurry though. Mine does lose bite in sharp turns though with the aluminum 4 blade from the factory. 3rd hole is probably best all around performance.

[fishon396]

I found Jacos Marine to have the best price at the time on the X7 props.

[ReefOctopus]

Mine came with the tabs on it. Surprised yours doesn't have them. I went to the 4th hole and haven't changed my prop yet, but I can now get 46-47 without porpoising. I expect I can get a couple mph better with a different prop. Not in any hurry though. Mine does lose bite in sharp turns though with the aluminum 4 blade from the factory. 3rd hole is probably best all around performance.

Thanks for the info. Im not looking to squeeze every last MPH out of the boat. I just want to be able to be in the MID 40's with a good ride. Im not breaking a speed records but 40 MPH is just under performing.

[ReefOctopus]

The SpitFire is 4 blade correct?