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yahoo
04-05-2006, 05:04 PM
I heard Merc was coming out with a sportmaster, anybody have an idea of when ?

150aintenuff
04-11-2006, 08:26 PM
some how i doubt that there is much of anything on the exterior different frm the 3.0L sporty, just deaper ratio i would assume since the verado is a totally different ratio than the previous engines..

tj309
04-19-2006, 08:33 PM
If I could get a Verado with a Sportmaster gearcase I would jump on it. I just lengthened my 2 PM300's (with Sportmasters) to 25" on my 24' cat to improve hole shot. I can still jack the motors to the original position for speed. So I may loose 2 mph but when you have 110 to play with who cares? Now I hope to have the hole shot of a ski boat with the top end of a race boat. Will it happen? Work in progress but I have already bet several thousand $ that it will.

MaDneSS
04-20-2006, 12:17 PM
BIT OF AN EXPENSIVE OPTION IN MY OPINION! WHY NOT JUST KNOCK THE PITCH OF THE PROPS DOWN A BIT :p :rolleyes:

tj309
04-20-2006, 06:15 PM
I didnt want to loose top end.

150aintenuff
04-21-2006, 12:23 AM
there are easier ways than puttin longer mids on a boat to get hole shot... prop choice for onething, lower the motors all the way on the jack beforeya lengthin them, and also change style of jackplates.. raising the center of gravity isnt something you want to do with a cat... and if your usin over hubs holeshot isnt their greatest atributes...

SUPERBASH
04-21-2006, 05:50 AM
I may loose 2 mph but when you have 110 to play with who cares?


I didnt want to loose top end

Which is it ???

And I agree. 25" is not the way to go.

pyro
04-21-2006, 05:57 AM
......

tj309
04-21-2006, 08:13 AM
2 MPH is minor. By changing props to a lower pitch I would loose more. The way the jacks were set the lowest setting put the propshaft 1.5" above the bottom - great for top end but bad for hole shot. Now I can jack down for hole shot and jack up to the original setting for top end. I am running 25 and 29.5" thru hub props with ventilation holes.

RBT
04-21-2006, 08:22 AM
how on earth with 5" longer motors give a better holeshot?

tj309
04-21-2006, 09:56 AM
by getting the props deeper in the water. Smaller tunnels such as a 21 ft Liberator with a pair of motors are set up exactly like mine now is. Before the jacks were useless in that the lowest setting was the highest I would want to run. So I guess they were there for trailering. Now they can be used properly.

RBT
04-21-2006, 09:57 AM
What kind of boat?

tj309
04-21-2006, 11:59 AM
24' Active Thunder Cat.

RBT
04-21-2006, 12:00 PM
well assuming you are using surfacing props, choppers or cleavers or the like, droping them will not help and more likely hurt the acceleration.

RT

tj309
04-21-2006, 08:59 PM
I am not using choppers or cleavers. Now lets get a few facts straight.

First of all I apologize for using this thread for this type of discussion. It just seemed to happen.

Second - you guys need a little more background as to what I have, what I need it to do, and what it should be able to do.

Third - I am not a boating rookie. Had my own boat before my own bike in the 60's. No I am not a race guru but I am an aeronautical engineer and hydronamics are not that different than aeronautics except the medium - water - is thicker (more dense) than air.

I have had many boats but my 3 favorites were my 18' Southwind with a 135 merc straight 6 (47mph), my first real boat - 10 ' GW Invader with 50 merc, and the Hydrodyne which I did not own but drove for a ski show - 18' w twin 115 Johnsons (0-40 in 4 sec - top end 45).

I was in the market for a new boat. The wife said get what you want. I have always wanted a tunnel and I love twin engine rigs so I found a 24 ft cat with twin 300's that was advertized to go 110. I did the math and that was a correct statement. Perfect right? Not exactly.

The new boat came with 32" cleavers and 17" of setback - 12 on the mounts and 5 with the jacks. The deck was 15' long. The 1st time I hit it the bow went up 45 degrees and stayed there forever and the minimum speed I could plane was 38. Needless to say it scared the hell out of my wife and I was not comfortable with this either. So how do you fix this? I went to the OSO forum and a guy named MWalters really helped me out. Start with the props. I did. Got a pair of Hydromotive Q-IV's at 29.5" and once I got them dialed in the hole shot, bow rise, and slow cruise speed all improved. Then I moved the batteries from the stern to the bow. This helped everything dramatically. I still wanted better hole shot so I got a pair of 25 Q-4's. This helped also obviously but now my top end is only 85 (96 with the 29.5's).

I am tired of sending my wife on the bow for better plane-off. Moving the batteries forward really helped but thats not the long term answer.

The 29.5" props rev to 5000 RPM on acceleration. They have ventilation holes. Sinking them deeper will reduce this to (I hope) the ideal 3000 RPM. Im still working on the 25's.

So I decided to move the helm 3' forward and put the batteries back in the stern. I was dissatisfied with the gauge arrangement and like the helm on the right side so as long as I am changing everything else why not do this? And gain 3' of cockpt?

The jacks. The way they are set up the lowest setting put my prop shafts 1.5" above the bottom of the lowest part of the cat hulls. Perfect for speed but bad for acceleration or hole shot. Also good for trailering but thats not what jacks are for. When the props are that high only the bottom half is working and contributes to the bow rise. Also ventilation ocurres which contributes to the lengthy time to plane. So I am sinking the props deeper to get more water to play with to improve both of these (bow rise and hole shot). Once I'm up on plane I can jack up to the low drag setting like it was before and still go fast.

Sorry for such a long post but I think you guys need to know where i'm coming from with my mods and why.

150aintenuff
04-22-2006, 01:32 AM
deaper wont stop ventilation to 5000 believe me..... my motor is BURRIED at 8" below and with 1" vent holes i cn bonce the lmiter ALL DAY LONG and never plane off... deep er is not the answer, smaller vent holes reduce the exhaust gasses around the blades and if the props stay hooked up on break over at 1.5" above lowering them wont do a dan thing... look to your props and try closing off the vent holes on the 29's and see what they do... i bet even at 1.5" above they still launch better than they would at a lower setting with the vents wide open... your problems are venting due to exhaust not excessive height.. try a 30 or 32P vented 1" every other blade set of bravo 1 4 blades... on a 250 the 2 1" holes vents to 4200, much lower and you go under the 3.0 L powerband and get the classic 3.0L bog on holeshot.

you may not be new to boating but there is SEVERAL aspects that make your solution incorrect, first off the only jackplate that lifts 6" is a BOBS and they arent rated for 300 hp or offshore style cat use... and when you go from a 20" mid to a 25" mid you actually gain 5.5" in total length.. so if your motors arent on the very lowest hole in the mounting bracket your forgetting height adjustments there as well..

if your props stay hooked up as the nose falls down to running attitude at the existing height you arent going to gain anything by going lower... except alot of lost speed and poor handeling because of a raised center of gravity..


do us all a favor and post a pic of the back quarter of your hull, with the jacks all the way down and anoter with them all the way up as it is with the 25" since you already spent the $$$ on them.. (waisted in my opinion) i am personally not a big fan of thru hubs on an outboard offshore boat due to the added sternlift they give in a hull that may not necessarly need any more... iassume that the props you went to are more of a round ear design as well, which is working against you as well.. cats have natural lift and need lift throughout their entire length to be up and flying, that is why your hull came with high rake over hub cleavers, the cleaver blade lifts the stern, and the rake angle of the blade lifts the bow and mid ship.. the more rounded the ear of the blade the more bow lift is produced taking lift away from the tunnels exit and causes excessive drag through the tunnels slowing down both holeshot, acceleration and top end...

through hub props with a long barrel will give stern lift needed to clear the tunnel exits and run clean, but it is going to be tough trying to make a hull design do something it was never ment to do... do you have a tunnel tab on the hull as well, or did you not think about that little piece of technology before swapping out to 25" motors...

300x Stoker
06-05-2006, 07:31 PM
I would put in wedges or re do the brackets for more transom angle. From your description it sounds like the motors are trimmed out too far on takeoff.

150aintenuff
06-06-2006, 12:02 AM
its a offshore cat.. thats their natural lift patern... they go nose high becausethe tail is dragging untill it planes off if it had a centerpod like your stoker it would handle different.... watch a Skater plane off when eased on plane versus a SST warlock.. you arent worried about loosing speed but you took a 110 MPH boat to 85 and removed 7" of pitch which is a RPM gain of 1400 or more.... your doing more damage by under proping than if you learn the quirks of a cat hull and work around them...

yahoo
04-08-2007, 10:39 AM
Any word on the sportmaster ? Especially now with the 300 coming