Custom 1965 Correct Craft Mustang build

Would it be possible to reset the prop shaft angle back to OEM spec?

Hussler wrote: SNobsessed wrote: Would it be possible to reset the prop shaft angle back to OEM spec? Not without cutting out the shaft log and some of my stringer floor supports.

Going back to the shaft angle that CC used would, in my opinion, be my recommendation. Installing "band aid" trim tabs as mentioned by several members may not work and in fact may create a dangerous handling problem.

But I'm guessing all motor mounts need to sit lower, pretty big task.

It will be interesting to hear what the tabs end up doing for you. I also like the idea of trying a different prop, I realize it's a bit limited for the older hulls but if you could find something a lot different you would find if the porpoise changed speeds or went away.

Hussler wrote: How can prop dimensions effect porpoiseing? I only get the porpoiseing between 43-48mph but it goes away completely after 48. Based on my experience with the Chris Craft the tabs will be a perfect solution for a loaded boat

Props with more aft rake which is typical of a CNC machined prop, produce more of a cone shape aft wash which has been reported to affect the attitude of hulls.

Based on my experience tabs are the worst thing you can do to a wood hull under about 26'.

I could see it making a pretty significant difference, especially on a 16 foot boat. A few degrees on a 21 foot boat, maybe not so much impact, but on a short boat like this a few degrees change in thrust angle could have a big effect.

Just thinking aloud, because of course I have no experience doing this myself, but I wonder if the largest diameter prop you can fit under there, with a pitch to match your peak rpm, might help. I'm just thinking the most blade area you can have might give the best result, even a 4 blade if that's possible on that boat. Again, just guessing.

Jim,
When you did the hull, did you remove any of the hook off the bottom? You measured and found the hull had about a 1/4" hook. Removing any of it can make a big difference.

Also, keep in mind previous warnings:

TRBenj wrote: No porpoising at 50mph is not something I would consider a positive. These hulls tend to get dangerous when they chine lock or rudder stall. Both of those happen when the nose is planted, not when its loose and bouncing. The higher riding, bouncing hulls are the fast ones, and theyre also safer at those speeds. Peter, Reid and Joe all had some scary things going on when they pushed nose-low hulls into the mid-50's. I think Peter's was the worst, it started doing weird things as low as the mid 40's. Every hull will ride a little differently, so there are few hard and fast rules.

BTW, my comment below was on a wood Chris Craft modified with trim tabs to get the bow down.

8122pbrainard wrote: Boats have flipped from the chine locking. A slight hull turning and the chine hooks the water and then the hull rolls. I have a close friend who almost lost his leg due to a chine hook and hull roll.

Again, I feel you will be modifying hull performance with the tabs that could be very dangerous.
Did you ever contact Peter (peter123) regarding his problems with a larger HP in his Mustang?

This hull can run fast relatively safely- when set up properly. I do not believe trim tabs are a means to that end.

Riley wrote: TRBenj wrote: This hull can run fast relatively safely- when set up properly. But someone still has to be the test pilot to figure out if it's set up properly.

Kind of like the old Mutual of Omaha Wild Kingdom - Marlin stays safely in the tree stand while Jim fights the wildebeest. Only in this case "let's film safely from shore while _______ (fill in Peter, Tim, Joe, Reid, etc.) drives the 16 ft. CC at 60 mph".

I'm using the trim tabs to accommodate more people

The trial and error of changing props, shaft angles ect. MAY solve the issue of having more people in the boat, or it could cause the boat to slow down, flip at high speed, who knows

Boat drives great with just me in it, the amount of time effort and money in changing the shaft angle and prop to possibly fix one problem, when I know for a Fact the tabs will solve it, doesn't make much sense to me

Jim, keep up the good work and let us know how the tabs work out.

Pete, was that question really necessary? When other guys on the site put more HP to their little hulls than they were ever intended to handle, I haven't seen you ask them about their insurance status.

I think you are missing some points. Jim sounds like a very experienced driver and someone who has worked on a lot of different hull types - he's not some yahoo slamming the throttle down and seeing what happens. He is trying to correct a porpoise happening at around 30. The idea isn't to put the tabs down at 50, in fact he says in an earlier post that he will warn the Chris Craft owner of the dangers of over-tabbing. I think he'll approach this cautiously.

Considering just about every inboard from the mid 90's to present was offered trim tabs from the factory it's not crazy to believe that the instances of bow steer and chine lock are relatively low on factory or modified boats. Especially considering I personally know about 80 people with inboards (about 20 with trim tabs) and the only accidents with injuries I've learned of were related to crashing into land (2 instances) or fire (1 instance). To negate trim tabs as a reputable solution is completely absurd and the fact that they do work isn't up for discussion in my thread because I have seen them work flawlessly to solve the exact problem I'm experiencing. I too thought them a poor solution, but only due to the stigma some have to them on this website, I found that my real world first hand experience they are a great solution.

If you feel that strongly against trim tabs, just leave my thread.


Now onto the tabs! My kit came in the mail today, some quick measurements assured me that I will be able to mount these below the waterline no problem, which is very important to me as I HATE the black plastic. May even paint all the black Perfection white, but that's much later on.

The tabs themselves are 12 wide by 4 long which obviously won't work, still have to decide if I'll cut and weld these tabs or buy 9x12s. It's 10 degrees outside so I'm not sure when I'll start this project.

Just realized I never showed you guys the two motors I got over the summer. The one out of the tan Mastercraft is a standard 351w PCM that was sitting for 12 years in Texas. It would need a total rebuild but is complete. The other is a 351w Holman Moody that kinda runs but needs lots of love, compression OK but fuel and ignition need a lot of work. Hoping to come across a first Gen mastercraft or first Gen nautique hull or barracuda for the Holman Moody someday. Both are in my tent with the boat. Both boats got brand new fully dressed chevys.

Before and after of the 84 mastercraft

Someone along the line added them to my Marauder....they are the manual type that are set with a bolt.......I have never tried setting them different and don't know if they make one bit of difference. I also don't get past 43-45 mph. But with a few people in the back at WOT it hops down the lake like a wild amusement park ride!