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1987 Checkmate Starflite 1998 Pro Max 300 Chine walk Concerns

S

superboop

New member
Hi guys, I've read just about every post on here for set-up for a Checkmate Starflite and am wondering if there are any suggestions to break the 80 mph mark. My boat is a 1987 with a newer interior done well but I would assume about as light as it was from the factory. I have one battery on the starboard side, oil tank on the port side, 30 gallon stock fuel tank in the center.

1998 Pro Max 300
6" hydraulic jack plate off of a Allison which I only know as it has Allison machined on the side
26p Trophy Plus prop
1.75 torque master LU
dual cable steering tightened to fight itself slightly
hot foot
mercury racing RPM gauge, autometer GPS speedometer
15 psi of water pressure

Top GPS speed achieved so far is 75.4 at 6000 RPM (RPM from when I glanced) with gnarly chine walk. Only me in the boat light chop with probably 8mph wind at my back. That would be prop slip of 10.66% (which is great, no?). I was running the motor at least 1" above the bottom of the V to achieve this. Rooster tail at about even with my cowling when I look in the rear view mirror.

Everything I read on here is the motor has to be roughly .5"-2" below the bottom of the V for top speeds. But if I run anywhere close to that the chine walk to is too bad for me. I've had the boat for two years and so have had a decent amount of seat time but no matter what I seem to do with the steering wheel I can't fix the chine walk before it happens when I get to 72-75mph. I tried running a 27p 3-blade TXP with my buddy in the boat to even out the weight but at .5" below the pad I couldn't pull the prop and struggled to get past 70MPH to where it would even start walking. Which surprised me. Best I could do is 71MPH at 5500 RPM 11.63% slip. My hope is going higher pitch was going to help me blast through the chine walk but even if I tried running the prop higher it would then just slip. I've tried turning the boat slightly as well but that hasn't seemed to help with the walk. Any prop suggestions that have helped with walk? Is running the motor as high as I am hurting top speed?
 
Even with the pad to 2” above the pad is the typical range for best speed. Lots of set back(often more is better) is helpful to reduce chinewalk. Zero play in the steering is vital to be able to drive/control the chine walk. A balanced boat side to side is helpful.

Now days, most would upgrade your steering to hydraulic (for safety and control) to go those speeds.

In essence you are just inputting enough steering to counter the boats natural tendency to fall off the pad to either one side or the other and you have to keep inputting those all the while.
 
So in the Starflite top speed thread just a few below this all the set-ups are saying prop shaft 2" below the bottom of the V. No one lists running above the V. So based on what you are saying I am fine to run up there.
 
Had a quick look at that thread, the 87mph boat has a lot of setback and prop centre line 1/2” below the V. You have proof your boat likes the engine higher than 2” below the V so what are you going to do? I suggest a prop happy with being surfaced like the Trophy plus and more setback.

BTW, Prop lower increases drag in the water, pretty hard to go fast with extra drag.
 
I'm going to go with a bit more set-back to hopefully help with the chine walk and gain some speed. Based on Jrumon boat he was running a 300 pro max so should be the same weight as mine. My jack plate is 5.5" CMC. Any issues bolting on a Bob's 4" or 6" setback plate between the transom and my CMC. My hull is rated for 250hp. Is that standard on any Starflight or were each transom's different? I have zero flex in my transom and there is no plate on the inside so I was thinking I would add 4" of set back with a plate on the inside.
 
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