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View Full Version : SWEET 16 Owners, BEST prop advice for 4.3LX



DONZI-DON
08-01-2014, 09:35 PM
Just bought a MINT 1994 "SWEET 16" with a 4.3LX and ALPHA ONE out-drive. I have only had the boat out twice. The last time (Tuesday) I was out I had My dad (161lbs), my friend (175lbs) and me (205lbs), 541lbs total. My buddy ask me if I had it WOT yet and I said not yet, he said no time like the present "HAMMER DOWN"! Keep in mind I have the "L-Seating" so both my dad and friend where in the back bench seat. She ran 57mph @ 5000rpm. I was floored. I couldn't believe it ran that fast with 3 of us and it only being a 4.3LX (262C.I.). The boat has a Quicksilver stainless 23 pitch prop.

Can some of you with this boat tell me what you are running for pitch on your prop and what your speed and rpm is at WOT.

The plastic cover on the carb states MAX RPM @ WOT 4400-4800, I was at 5000rpm. Is this harming the motor? What is the top speed of these boats with the 4.3LX at safe WOT & rpm?

Also I own a 15'4" THUNDERBIRD FORMULA (Cathedral Hull) for 15 years and I haven't owned a boat in the last 12 years until this DONZI purchase. I am amazed at well this boat handles rough water. The last time I was out it was a windy day and in the Niagara River (Buffalo) gets very choppy easy. this day it was easily a 2' chop/rollers and I was surprised how well the boat handled the water. anything less than 40mph you could feel the waves. once I got the boat to 40-45mph the boat road over the top of the waves/rollers and it was a very smooth ride.

woobs
08-01-2014, 10:00 PM
Factory WOT is spec'd at 4,800 rpm. I don't think 5,000 for a short burst would hurt too much (how accurate is your tachometer ?) My 4.3 ran up to 5,200 without harm but, it is fresh and has roller rockers.

Was your 57mph read on a GPS? Seems to me like your boat is already dialed in pretty well. By my calculator using your numbers (assuming the standard V6 Merc 1.84 gears); you are running less than 5% slip on your prop.

Even if it is not a GPS speed and the tach is off a touch your boat is running quick (with 540lbs). Nice.


23
x
5,000
=
115,000.00
=
59.2

0.95

56.2


1.84
x
1,056
1,943.04

DONZI-DON
08-01-2014, 10:09 PM
Sean,

Thanks for the quick reply. Yea the guy I bought the boat from said he owned 5 SWEET 16's prior to this one. Really seemed honest and very knowledgeable. We agreed he would have to put the boat in the water for me to purchase if I liked it which I did. He could def drive because it was a choppy day and I was surprised at some of the waves he was taking.

He said that the boat was set up for max performance as far as prop selection. I'm guessing he was right by what you are re-instating.

I guess the only concern I have is will I do the motor damage if I run at WOT at 5000rpm's. What would you consider running to long at, at that RPM (time wise)?

Thanks for the advice in advance,

Don

woobs
08-01-2014, 10:39 PM
Some say that if you keep it to 4,800 (in spec) you can run all day.... the question comes when you look at the life of your engine. Race engines that spend most of their time at WOT are not expected to last near as long as a recreational engine. More time at WOT less overall engine life... well, that's the theory.

I'm not the guy to answer how long you can keep it pinned as I probably run most of the time around 3,500 - 4,000 rpm. I'm usually only at WOT for a thrill when the lake is glass to see what I'll get out of her (if the conditions aren't perfect, what's the point). There are way too many boats much faster than mine to worry about trying to run with all of them. Plus, I run a pulling prop (high five).

Although, I must admit there's one or two of my friends who have boats close to my boat (speed wise) and I like to pull away on them from time to time but, I'd say it's less than 5 minutes at any one time... I have to let them catch up :) .... and of course there's one guy I almost never catch. he pulls away so annoyingly slow I want to jump in the water and change props right there! But, I'll live with it.

I'm sure there are more than a few here that spend a lot of time at WOT... just not me.

Ghost
08-01-2014, 10:43 PM
Sean,


Thanks for the quick reply. Yea the guy I bought the boat from said he owned 5 SWEET 16's prior to this one. Really seemed honest and very knowledgeable. We agreed he would have to put the boat in the water for me to purchase if I liked it which I did. He could def drive because it was a choppy day and I was surprised at some of the waves he was taking.


He said that the boat was set up for max performance as far as prop selection. I'm guessing he was right by what you are re-instating.


I guess the only concern I have is will I do the motor damage if I run at WOT at 5000rpm's. What would you consider running to long at, at that RPM (time wise)?


Thanks for the advice in advance,


Don



The factory spec for most v8 motors' max continuous operating RPM is 3500-3800 (tel:3500-3800), right? About 3/4 of WOT rpm. I'd guess v6 motors aren't much different, but I don't claim to know.

woobs
08-01-2014, 10:50 PM
The factory spec for most v8 motors' max continuous operating RPM is 3500-3800, right? About 3/4 of WOT rpm. I'd guess v6 motors aren't much different, but I don't claim to know.

I assume it would be similar. Never really paid attention as I'm not WOT too much. I also watch my gauges (almost anal about it).

3/4 continuous operation for any gas motor makes sense though. I think diesels may be different.

DONZI-DON
08-01-2014, 10:51 PM
Honestly, with my last boat I usually ran between 30-35mph. if I opened her up it was like you said 5 min max at a time and it will probably be the same practice with this boat. It's just nice to feel her at WOT FROM TIME-TO-TIME!