Merc V8 Re-Prop

QBhoy

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I stand corrected if that is the ratio...you Defo need at least a 21? then...if not a 23?.
I was wrong in thinking it might be a 1.47 with that engine and boat package. Perhaps it is because it isn?t an MPI.
 

Scott Danforth

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I stand corrected if that is the ratio...you Defo need at least a 21” then...if not a 23”.
I was wrong in thinking it might be a 1.47 with that engine and boat package. Perhaps it is because it isn’t an MPI.

No, the carbed 5.0 with a 1.62 ratio in his boat is a 19p at best. More pitch and he needs more motor
 

Scott Danforth

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Hi Scott

There are 4.3’s with that drive in similar boats running a 21”, that I know of.

Im talking from first hand knowledge based on my ReaRay 190 with the same motor and drive.

Boats have similar hulls, similar weight, sumilar performance
 

krakatoa

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No tested yet but got a great deal on a brand new prop 14.125 x 19 just for $30.00 cant let it pass.

Anyway
hopefully next weekend for sure. Now there is a few testing in line, Will test first with same prop to know about the "falling flapper" this one already in place wit hthe grommet , then test again with the new prop. It will be interesting..

Coming up more pics of testing including Rpm, Speed, Screenshots and some videos.



tumblr_p0reo9b6x31wg5vyfo1_1280.jpg





tumblr_p0reo9b6x31wg5vyfo2_1280.jpg



tumblr_p0reo9b6x31wg5vyfo3_1280.jpg
 
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porscheguy

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Cant knock that for $30. I forgot about let go as a source
 
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krakatoa

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Just for keep up with the info I email General Propeller thru a web form they have on the website with the required info. Here is the reply they sent this morning.

Copy and paste as follows:


[FONT=&quot]Hello Sir[/FONT]

[FONT=&quot]It seems that the propeller is too high in pitch, therefore you are not reaching the rated rpm under load.[/FONT]
[FONT=&quot]You need to get the same propeller on 17 pitch (difficult since these propellers, the Offshore series, are discontinued).[/FONT]
[FONT=&quot]Or maybe get a 3 blade in a 19 pitch, Mercury Silverado or an "Apollo 14 . 125 x 19."[/FONT]
[FONT=&quot]We do have the Michigan Apollo 993044 and the XHS hub (needed for installation) for a combined price of $304.20[/FONT]
[FONT=&quot]Let me know if any questions![/FONT]

[FONT=&quot]Pablo Soto
General Propeller Company
1415 9[SUP]th[/SUP] Ave East
Bradenton, FL 34208
941-748-1527[/FONT]





Looks like Im going in the right direction, anyway prop size was advised earlier in this thread. The Apollo prop he mention was the one that I got for 30.00 bucks last weekend.
 

Scott Danforth

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any why havent you put the boat in the water to test yet?
 

jkust

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Your Chaparral Extended V plane hull is the same as mine and my previous Chaparral and the same as they used for the next decade on their boats. Some hulls have a 2000 patent date and and I think some have a 2002 date on them. I'm thinking you have what should be a 50mph boat loaded up. My previous Chap was a 48mph boat with a 4.3 liter 21inch prop which weighed within a hundred lbs of your model and so was a bit underpowered but was a bit newer and my current which is heavier but has a larger engine is substantially faster on top and bottom end. Maybe I could have eeked a couple more mph out of that 4.3 at the expense of the bottom end. The current boat has a lot left to give as it is propped for out of the hole. I'm curious how this all works out.
 

krakatoa

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Your Chaparral Extended V plane hull is the same as mine and my previous Chaparral and the same as they used for the next decade on their boats. Some hulls have a 2000 patent date and and I think some have a 2002 date on them. I'm thinking you have what should be a 50mph boat loaded up. My previous Chap was a 48mph boat with a 4.3 liter 21inch prop which weighed within a hundred lbs of your model and so was a bit underpowered but was a bit newer and my current which is heavier but has a larger engine is substantially faster on top and bottom end. Maybe I could have eeked a couple more mph out of that 4.3 at the expense of the bottom end. The current boat has a lot left to give as it is propped for out of the hole. I'm curious how this all works out.

Interesting info. Which ratio do you had in your setup to turning a 21pitch with a 4.3 and goes close to 50 mph.
Actually this boat weight 3221 pds per specifications, its a heavy hull without mention 46 gal on gas. But yeah Im still curious too and cant wait to put it ln the water this weekend just to
Just to push the throttle down
 

Scott Danforth

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Interesting info. Which ratio do you had in your setup to turning a 21pitch with a 4.3 and goes close to 50 mph.
Actually this boat weight 3221 pds per specifications, its a heavy hull without mention 46 gal on gas. But yeah Im still curious too and cant wait to put it ln the water this weekend just to
Just to push the throttle down

the 4.3's with the 1.84:1 ratio and 21p prop are actually faster than the 5.0/1.62 ratio/19p. the larger bore than the 5.0 gives it a nice looking torque curve

the 5.0 needs a 4-barrel and a slightly different cam, along with some head port work to make it shine, especially with the smaller bores.
 

jkust

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Interesting info. Which ratio do you had in your setup to turning a 21pitch with a 4.3 and goes close to 50 mph.
Actually this boat weight 3221 pds per specifications, its a heavy hull without mention 46 gal on gas. But yeah Im still curious too and cant wait to put it ln the water this weekend just to
Just to push the throttle down

It was a 1.81 ratio carbed 4.3. Best I could get was 51.6 gps but that was just me with almost no fuel and medium gear with 21" alum prop. Boat was 3100 dry but only 33 gal gas tank. The vv is more robust than youd expect. Current 5.7 liter mpi with 1.50 bravo 1....so much more powet with a much heavier boat an 60 gallon gas tank...it just wants to run and is unphased by the load of passengers, gas or gear. The official testing had it at 59 gps with a slower B3 vs a little more on top end with bravo 1. You should be at least low 50's.
 

QBhoy

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the 4.3's with the 1.84:1 ratio and 21p prop are actually faster than the 5.0/1.62 ratio/19p. the larger bore than the 5.0 gives it a nice looking torque curve

the 5.0 needs a 4-barrel and a slightly different cam, along with some head port work to make it shine, especially with the smaller bores.

Surely not Scott ? No reason to doubt you other than what common sense would dictate.
 

porscheguy

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Bumping this because temps in your neighborhood have been in the mid 70s while the rest of us are freezing. Anything to report?
 

krakatoa

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welll finally can hit the water yesterday to test the boat again regarding the RPM issue. Can tell after removing the flapper from the bottom of the exhaust, install a new prop 3 blade 14 1/4 x 19 the boat can reach rpm up to 4400-4600-4800.

Need to mention that also installed new SX Smart Trim Tabs. Take a look to the pictures please. Better I did was
45.6 mph around 4600 rpm, boat moves great for me but need to found those 5 mph missing. Maybe refreshing or some tune up to the engine. Also the test was performed with the new Apollo Prop. Next time will put it back the 4 blade prop the boat came with. So guys what you think about it?

Prop: Apollo - 993044 - 14.25 x 19
SX Smart Tabs - SX9510-80
(Start on #3 per specs but feels to stiff, then went to hole #1, its is an 80 lbs gas strut)








415.6 MPH






RPM 4600


SX Trim Tabs




SX Trim Tabs 2




SX Trim Tabs  - works well with the ladder
 
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Maclin

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Have you tried going out with just the prop change? Or is your testing after both things were installed, tabs and prop? Will be difficult to divine between the changes. I believe Nauticus recommends dialing the boat in for a prop first without the tabs, then go with the tabs for specific bow-rise and hole shot issues. In a lot of cases the top speed is affected by tabs and may not be able to be tuned out by changing strut pressures or tab holes.

I would try without the tabs to see what the new prop does on the boat. You can get different brackets for the tabs that allow you to move the tab up out of the water without removing them.
 

krakatoa

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Have you tried going out with just the prop change? Or is your testing after both things were installed, tabs and prop? Will be difficult to divine between the changes. I believe Nauticus recommends dialing the boat in for a prop first without the tabs, then go with the tabs for specific bow-rise and hole shot issues. In a lot of cases the top speed is affected by tabs and may not be able to be tuned out by changing strut pressures or tab holes.

I would try without the tabs to see what the new prop does on the boat. You can get different brackets for the tabs that allow you to move the tab up out of the water without removing them.

The test was performed with tabs and new prop installed, but still cann remoce the tab and put it back again with no problem in the water. For sure I will write it down in the list when testing the 4 blade prop too.

I can tell this boat is slow as hell coming out from the hole with tabs or without it
 

alldodge

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Went back thru the thread so to restate where we started
4-blade 19 at 4100 rpm

now 3-blade 19 and your getting 3 different rpms (4400-4600-4800) at WOT so this tells me your trim is incorrect and/or your smart (dumb) tabs are causing some ventilation.

Tabs spring loaded of powered cause drag and lift at any position other then full up. As Maclin mentioned, in order to find the issue(s) we need to change one thing at a time.

Best way to find Max WOT with a prop, is place the tabs full up (or take them off) and place the cavitation plate flat an level with the keel. With both items flat and even we can get true numbers for slip.
 
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