Would a prop change help?

[hole-in-the-water]

Do I have the right prop? (Fairly new to boating)

Performance issue I am trying to correct: (see below)
Current prop: Aluminum / 14 1/2" / 21 p (with a few nicks)
WOT: WOT = 3,100 @ 37 mph (plenty fast enough for me)

2,000 @ 20 mph boat planes out​

2,500 @ 30 MPH - skiing speed (NOTE) During turns (pulling skier) - drops to 26 MPH​

Engine: 1992 Mercruiser 4.3LX (4 barrel) HP: = 190 (?) - Thunderbolt IV
Boat: 1992 Bayliner - 21 foot - bowrider - 2150 (dry) weight - Outdrive: Alpha I gen 2 Ratio:1.81:1

Issue / Question:

I bought the boat used. Runs great (starts right up) - When I am pulling my son (150 lbs) he pops right up on 2 skis and I barely feel him. When he slaloms - The boat seems to really struggle to get him up. Also when I make turns the boat slows down about 4-5 MPH (not a sharp turn)​

I am looking for more hole-shot (I think) - not so much concerned about top speed as we have a 35 mph speed limit on our lake (private). I am pretty sure the WOT for this boat is 4,400

Suggestions appreciated

 

[QC]

Re: Would a prop change help?

First thing that jumps out is I believe your tach is wrong. To be clear, at least one number is wrong. Speed, RPM, Gear ratio or pitch as stated. Experience says must likely it is the tach, or the speed, or both. Is that GPS? How I know this is that the speed as shown is faster than the pitch x ratio x RPM can physically go.

So let's get that right first and then talk about potential changes to get what you need. There is usually a switch on the back of the tachometer. First thing is to make sure it is set for a 6 cylinder engine. Also, tell us how you got your speed.

 

[steelespike]

Re: Would a prop change help?

Probably a couple of things going on. To go 37 you would have to turn about 3700 rpm. So either the speed is wrong or the tach is off low.
From your description I wonder if the boat us running on 5 cylinders as well?
As setup the boat should run about 48 at 4800 rpm.
Slowing in turns is normal; I believe left more than right.The excessive slowing is an indication of a lack of full power.(5 cylinders?)
Of course a lack of power could be any number of things Something in your description just said
(5 cylinders.) also check that the throttle opens all the way,Timing set right and advancing as it should.

 

[hole-in-the-water]

Re: Would a prop change help?

Let me check (when I get home tonight).

It IS a new tach and I assumed it was set for 6 cylinder.

One step at a time.

 

[QC]

Re: Would a prop change help?

One step at a time.

Smartest post on this site. Should be a sticky