Merc V8 Re-Prop

[krakatoa]

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.

The three diferents RPM was depending on trim position, so I spot the 45.6 mph around 4600 rpms. Wen I start this thread the boat cant do more than 4000-4100rpm. so now the following will be:

1 test the boat with no smart tabs and the 4blade prop, lets see what happen.....

maybe the tabs grab my missing 5 mph to reach 50mph, but not really sure cause the boat feels nice and free its not like dragging something.

 

[Scott06]

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

If you want better holeshot try putting the 4 blade back on, you will loose some top end (I loose 3 mph 4 blade vs 3 blade) but i tend to have 4-6 people skiiing tubing or wake boarding, so I stick with a 4 blade.

 

[krakatoa]

If you want better holeshot try putting the 4 blade back on, you will loose some top end (I loose 3 mph 4 blade vs 3 blade) but i tend to have 4-6 people skiiing tubing or wake boarding, so I stick with a 4 blade.

is another test I will do next time on water, as mentioned before anyway at the end of the day Immnot into skiing or tubing just want hit top speed and fastest hold shot for this boat.

 

[Maclin]

What specifics about the boat's performance made you get the tabs?

Asking because that boat has the extended v-plane hull, which does some of the things the Smart tabs aim at. With the V-plane hull, that type of tab may somewhat redundant. Once you are ready to dial in the tabs, do not be shy about contacting Nauticus with your results and get their recommendations, I am sure they know about the V-plane and how their product behaves with it. You may be able to use the 60lb actuators rather than the 80lb ones usually recommended for a boat that size and power. They will swap out actuators at no charge I believe, if that is their recommendation.

Here is an expert's review of that feature on your boat...

Case Study: Chaparral's Extended V-Plane
There are two ways to describe Chaparral's approach: lengthen the hull to wrap around the outdrive of its I/O boats, or draw the center portion of the transom forward within the hull. Either way, you're getting full use of your boat's length. This has less to do with faster top speeds and more to do with the ability to jump onto plane quicker and stay on plane at slower speeds.

 

[porscheguy]

Pull the tabs off when doing top speed runs. The tabs produce drag. When you say it’s slow to accelerate can you elaborate on that?

 

[krakatoa]

What specifics about the boat's performance made you get the tabs?

Asking because that boat has the extended v-plane hull, which does some of the things the Smart tabs aim at. With the V-plane hull, that type of tab may somewhat redundant. Once you are ready to dial in the tabs, do not be shy about contacting Nauticus with your results and get their recommendations, I am sure they know about the V-plane and how their product behaves with it. You may be able to use the 60lb actuators rather than the 80lb ones usually recommended for a boat that size and power. They will swap out actuators at no charge I believe, if that is their recommendation.

Here is an expert's review of that feature on your boat...

Case Study: Chaparral's Extended V-Plane
There are two ways to describe Chaparral's approach: lengthen the hull to wrap around the outdrive of its I/O boats, or draw the center portion of the transom forward within the hull. Either way, you're getting full use of your boat's length. This has less to do with faster top speeds and more to do with the ability to jump onto plane quicker and stay on plane at slower speeds.

at low speed the bow is so high that I have no visibilty, have to stand up from the bucket seat to see something
no zigzag at 5 mph, quick plane in no time when getting out of the hole. But yeah Its a nice addition for performance , no doubt. but still looking forward on choppy waters.

One might right regarding the 60 lbs actuator,(actual are 80)I start on pos #3 on the tabs per specs but the boat feels so stiff, have to go to #1 for better performance.

 

[Scott Danforth]

just want hit top speed and fastest hold shot for this boat.

fastest hole shot and top speed are on opposite ends of the spectrum. you can have one, not both. for fastest hole shot, a 15x15p will shoot you out of the water, however you will over-rev on the top end. for a good all around prop, you move to a 15 x 19P and you have an OK top end and an OK holeshot. for best top end, you need to sacrifice the lower end.

 

[Scott Danforth]

also, forgot to add..... the best thing I did for my SeaRay was a set of Bennett sport tabs.

 

[Scott06]

A little confused by the comments Karakota in post 59 you state " I can tell this boat is slow as hell coming out from the hole with tabs or without it" , but then in post 66 " quick plane in no time getting out of the hole" . Which problem are u trying to correct, as scott states generally you get one or the other. A prop that is ok on holeshot and ok on top end is perfectly suited. It generally you are sacrificing one or the other

 

[QBhoy]

Totally bewildered by the details of this post.

 

[krakatoa]

A little confused by the comments Karakota in post 59 you state " I can tell this boat is slow as hell coming out from the hole with tabs or without it" , but then in post 66 " quick plane in no time getting out of the hole" . Which problem are u trying to correct, as scott states generally you get one or the other. A prop that is ok on holeshot and ok on top end is perfectly suited. It generally you are sacrificing one or the other

Ok let me explain... just want to tell that the boat is pretty heavy, without the tabs you were looking to the sky when start hitting the throttle, from 0 rpm to 4100 cause the boat raised the bow so high that visibility was practically 0, of course the exhaust was clogged cause the flapper fell.

Now with the flapper in place and with smart tabs bow raise is practically 0

 

[krakatoa]

Totally bewildered by the details of this post.

Ok let me take you back to trail......

1.First problem here was the boat feels like dragging something cause max RPM 4100. Speed feels like 35mph
(Per Specifications this setup has to be in 4400-4800 RPM and 50 mph)

2. First concern was the prop because usually boat that handle 4 blade props are lightweight bass boat with a big HP Outboards.

3.Mr. Scott Danforth mention in this thread after a few prop recommendations to look for a possible clogged exhaust, do by a flapper dropped in the y-pipe so I check it and found the flapper off place all the way down the pipe.

4. Once Flapper in place follow the prop recomendation and went with same prop but 3 blades instead 4.

5. Smart Tabs installed cause Santa bring them : )

6. When test performed the boat ran faster 44.5 or 45 mph (check pics above) and 4600-4800 rpm depending trim setup

Thats means that the 4100 rpm and dragging speed when thread start was resolved. Only question is if the 4 blade prop could be a difference because the test was with the 3 blade prop

For a 3221 lbs boat without gear It can not do from 0 to 50 in 10 seconds, thats why I said this boat is slow getting out from the hole. Remember the ratio is 1.62 If 1.82 with a 23P PROP is a different story.

Anyway iI will test the 4 blade soon so I will be back in this topic with the end of the story.

Got it?

 

[QBhoy]

Easy on....maybe just me !

 

[krakatoa]

Easy on....maybe just me !