2019 Crestliner vt18 porpoising questions

[ChooChooSnakeMan]

I used to own a 17’ 6” Triton tin boat, pad hull, with a 90 hp Optimax and having additional cup added to the Laser 2 prop and mounting the motor on the 3rd hole was a good combination. The combo was good for 47 mph in summer and 50 mph in cool weather.

Thanks for the suggestion on the prop. I'm going to talk to our local prop guy and see if he thinks he can cup the prop as you describe. If I could get a 40 mph cruise speed on gps I'd be very, very happy. Thanks again!

[gaf11]

I have a 2010 Crestliner Fish hawk 17.5 foot deep Vee rig with a 90 hp Mercury. It would porpoise badly at 3500-4800 RPM. I installed one of these after my fishing partner tried one out. https://www.hydro-shield.com/

My proposing stopped at all RPM ranges completely. Much better hole shot also which I didn't expect. Protects your prop and lower unit in the process. I just got back from 1 week of fishing live bait below Wilson Dam in Alabama and it saved my prop several times from damages.

[Extremeboating]

Raise your motor up a hole and see where it lands. You probably need a different pitch prop also but I would raise the motor up to start. The 75 HP motors and up need to be on the third hole usually.

[CAPTAINRUSTY]

I have the same setup as you do snake man. I put a mercury spitfire x7 19p on it and it helped tremendously , but it still is touchy and doesn’t take much to get it to bounce. My motor is mounted second hole from top, but I’m planning on raising it to the 3rd hole to see if that helps even more and to see if my rpms come up some. I’m only getting about 5300 to 5400 rpms out of it. I get an easy 40mph cruise speed with this prop with no porposing.

[Bc12point]

I’m looking for some suggestions. I’m looking to purchase a 2017 VT 18 DX. It is a garage kept, well maintained boat with very little hours. Has the Mercury 90 but some other extras that make it a good deal. Also found a decent 2018 but fewer extras. My questions are….
is there a real difference between 17 and 18 models?
should I run from this boat due to porpoising issues or be confident that it’s a good boat?
i realize it doesn’t have the 115 but I’m not trying to go 75 on the water anymore. Just want to fish comfortably.

[reelfast]

I had a 2015 VT 18 for 3 years and went to the 21 pitch Lazer II prop RPM's to 5900 and 52 to 53 mph with the 115 Merc.

Then learn to trim up and down depending on how fast you are going to minimize the purposing issues.

[Bassooka]

I’m looking for some suggestions. I’m looking to purchase a 2017 VT 18 DX. It is a garage kept, well maintained boat with very little hours. Has the Mercury 90 but some other extras that make it a good deal. Also found a decent 2018 but fewer extras. My questions are….
is there a real difference between 17 and 18 models?
should I run from this boat due to porpoising issues or be confident that it’s a good boat?
i realize it doesn’t have the 115 but I’m not trying to go 75 on the water anymore. Just want to fish comfortably.

Take the boat out for a ride and see how it performs. You should know pretty quickly if it porpoises.

[danb303]

I had the motor raised one hole and they glued on two small aluminum wedges on the bottom. One fell off the first time out. It certainly helped with the porpoising issue. It now seems like the prop slips occasionally especially in turns. I assume raising the motor up one hole has the prop close to the top of the water.

[danb303]

After the fix I could get 48 mph before porpoising started. I was only able to turn 5700 RPM. I went to the Spitfire x7 stainless 4 blade 17p and now I am right at 6000 rpm but I lost 2 mph down to 46.. With the 4 blade prop I don't seem to drop as many MPH when I am loaded heavy. My top speed has been 46 but I can add a co-angler, full tank of gas, full live well and still get 45 mph

[Extremeboating]

After the fix I could get 48 mph before porpoising started. I was only able to turn 5700 RPM. I went to the Spitfire x7 stainless 4 blade 17p and now I am right at 6000 rpm but I lost 2 mph down to 46.. With the 4 blade prop I don't seem to drop as many MPH when I am loaded heavy. My top speed has been 46 but I can add a co-angler, full tank of gas, full live well and still get 45 mph

You may need either a jackplate or wedges, potentially even both.

[ReefOctopus]

I think alot of people with aluminum boats need to realize that they are not running high performance speed machines. These boats really shine once the trolling motor is down. Trying to squeeze a few MPH is not worth it. Fixing a porpoising issue is fine but if we want high speed rigs, just go to fiberglass or a niche aluminum brand.