Vision221 overtrim for best Top speed

[Gimme Fuel]

How do you guy's verify the Bravo travel ?

Could have been doing it wrong .... since I am Canadian and all

Thanks for prop selection/suggestion you just listed Gimme Fuel that gives me something to look for !

I think the Mirage Plus SS is repaired since it seems a lil rough around the blade tips , it's also just a 23 ... Maybe a 25 Mirage plus SS would do ?

I agree the 25P quicksilver on there right now does look like a cheap'ish prop , the blades are thinner than the Mirage and less cup for sure.

If your RPM's are in the right range with your current 25p, a 25p mirage will probably loose 100-200 rpm. They turn more like a 26p.

A Bravo I will turn about 1" pitch less than stated. IE a 24p would rpm's similar to average 23p.

A Revolution 4 will turn roughly +1" pitch higher than what is stamped. IE a 23p would turn RPM similar to a average 24p.

Keep those in mind too when prop shopping/testing. Not all pitches are created equal. The added cupping of some prop types loads the engine much more than say a straight cleaver or something with small amounts of cup like your average Hydromotive QIV. Those turn usually -1" to -2" pitch less than stamped.

If your 23p Mirage is only slightly too small, most good repair/lab shops can twist the pitch up also (since it is getting repaired anyways) to 24-24.5"p.


This thread is a good read if you want to learn more on the subtle prop differences:
http://checkmate-boats.com/forums/showthread.php?t=24318


First off, I would say that you need to find a Merc service manual somewhere and verify your trim limit settings. If you are currently set within spec, then proceed with prop changes. If not, reset and get a good baseline of where you stand with the proper trim settings then test other props. Remember, a Bravo does not like to be overtrimmed nearly as much as an alpha unit. The range of usable motion is much less due to the components being larger.

 

[ram750]

Thank you so much for the prop crash course ! I knew a little bit about different prop loading and running differently.

Do you think increased stern lift prop would free some drag up from the hull being higher and release a few mph's ?

If so I would try to get a prop that will drop rpm's / give room for more speed.

 

[Gimme Fuel]

Typically Checkmate hulls do not like a lot of stern lift (not all were pads though, some straight V). The pad bottom hulls adequately lift the stern on their own. They typically like bow lift to help the boat rise up on the pad at speed. Too much stern lift lends for squirrely handling and an unsettled stern while almost forcing the keel into the water giving a increase in wetted hull surface causing "bow steer". The typical through hub prop barrel added with the paddle wheel effect of the blades helps to lift the stern enough on a CM hull. The longer barrels (like some Bravo I and Maximus models) can be cut down to help settle the stern a bit. Small or over-the-hub props will provide the least amount of stern lift but still will provide some (these are almost always outboard props). Bravo I are a heavy stern lift with low-moderate bow lift characteristics however cupping can be added to make a CM hull very happy and most of the really fast CM's run a labbed Bravo I.

Remember also that "labbing" is a general term for any kind of worked over prop. This can range from the typical blade thinning (what most think of as a lab job) to added/reduced cup, increased/decreased rake angles, cut down diameter, and trimmed diffuser rings. Each hull is unique and likes a certain "recipe" of the aforementioned prop modifications.

Another way to test props and lift characteristics is to have someone run alongside of you (safe distance of course) and snap a few pics of your boat running WOT and trimmed optimally. This will let you see the running attitude the prop is giving you and will let you judge how much of the hull surface is wet. Less hull in the water = higher top end numbers....but go too far and handling becomes an issue. When going for 70+ mph and running a lot of time WOT, external hydraulic steering rams is needed especially if your hull has a tendency to chine walk.

Typically you want to keep your RPM's in the upper portion of your listed WOT rpm range. Your mag motor probably is listed for between 4700-4900 WOT? so being around 4800-4900 should be your goal when propping. If you are under propped currently stepping up a pitch can get you more speed without dropping your rpm too much. But if you step up and it drags your motor down below the 4700, that is too much prop. Propping is one of those things where you don't know if you don't try it! With your boat being a 22' I would imagine a Mirage prop would give you the best top end. If you spend more time cruising a 4-blade would be your best bet. Under 70 mph CM's do quite well with stock Bravo I (but probably be couple mph slower WOT than mirage). Trying to get them above that they typically like some added bow lift on Bravo I props. Your boat is also small enough you might be able to do well with the Trophy+ like Brianh stated. Typically most hulls larger than what you have need the larger 15+" diameter to cut the slip percentages down.

 

[Kurtster]

Great info/analysis Ron.......

 

[ckaluger]

We had a local guy spend 18K on a supercharged big block for his Vision and the best he could do was 73. he was frustrated, I am not that familiar with the Vision hull, but of it is anything like the Starliner no pad, they just do not want go much beyond 75.

Good Luck!!

 

[ram750]

Gimme fuel !!! Wow thanks Man !!!

Great info and its amazing because between my old Baja 210 ESS and my Senator Big Block ( 19' + swim platform ) and now my Vision 221 I can recognize some of the handling and riding characteristic you mentioned.

You really know your stuf Sir !

From what you have said , I am gonna try and find some Mirage or Mirage SS plus around 24-25 pitch. The boat planes in a couple feet anyways even fully loaded thanks to the tabs , so don't see the point to hunt for the bravo 1. Probably concentrate more on top end gain's. ! I will also make sure to re-check the trim cylinder distance .21" is what I set it to as per a quicksilver trim pot replacement paper I got a while ago from a friends boat I repaired. I just found online someone quoting 21.75" being the right distance.

ckaluger , thanks for the luck I will need it cuz in Quebec where I am from it's slim picking for go-fast props or parts :/ About your local guy with the S/C'ed Vision , that could be other things limiting him like a badly tuned engine. I mess with car's alot and 95% of the time the biggest budget build run 1/4 of the speed a well tuned car does.

 

[Problem Child]

I have a Mirage 27p I would lend to you but I dont think it will help you out. Your gps speeds sound very respectable at 69.5 and hope you can find that couple more you are seeking. Christo680 has a nice BBC Vision on here and you can get some good info from him as he has been prop testing all last year dialing in his new powerplant. He is a great guy and might even have what you are looking for . Best of luck. Jeff

Also I think your limit switches are possibly out of adjustment as trimming past override sounds a little scary. Getting a big rooster out of a Bravo is rare but possible I guess. Viper 1 has been way into the triple digits with his Sweet Vision Hull. They are made for High Speed Water Rocketry.

 

[Gimme Fuel]

You might want to jump over to offshoreonly.com and check out the swap shop there. There are always prop trading and selling going on there. Usually all good people to deal with too. I've done many deals on there.

Matter of fact:
http://www.offshoreonly.com/forums/swap-shop/307372-mercury-mirage-plus-25p-labbed-prop.html
http://www.offshoreonly.com/forums/swap-shop/304000-mirage-25-rh-used.html


BTW mirages only come in odd numbered pitches. IE 23", 25". to get a 24" it would have to be tweaked by a shop. Grab a 25" and see what that gets. If it is too big you can have it bent down or have your 23 bent up. Kinda sucks falling in between. Generally you are better off being a little too small than a little too big. Not the case with women though...haha.

Usually a few nice supercharger packages that would fit on top of that mag motor real nice too....just sayin!

 

[Kurtster]

but if it is anything like the Starliner no pad, they just do not want go much beyond 75.

Good Luck!!

More HP / More tourque / More RPMs / More balls / = any speed you want

I know of a few 221 Visions that have well surpassed 80+ {unfortunately mine is not one of them}

Regardless of the hull {pad / no pad / blueprinted / not blueprinted / etc...} --- if you got the jewels and the know how, you can make the Vision reach {and surpass} triple digits.

 

[ram750]

How solid is a mag 365 hp 454 ? rods , hardware and piston's can take 5-6lbs of boost ?

I hardly understand carburators so a little nervous even thinking about tuning boost on a blower setup ....

BTW , turn's out a friends dad apparently has a shed full of 25-26 pitch props ! 3 of each !!! He owns a couple boats ... big $$$ boats and his old beater baja 420 with 3x502/500 had been messed with so much to find the best prop that he as a shed full .... a couple bravo's , but mostly some Mirage and Mirage plus !!! I know who I am visiting when spring rolls around !

 

[Gimme Fuel]

Awesome having friends with spare parts!

If you have the 365 hp mag motor, that is a very stout platform. It can handle 5 lbs boost easily. What compression ratio it has will yell better on that though....i dont know specs off hand for older carb stuff haha. You could probably find a cam and weiand 177 blower setup cheap enough and build a 525sc clone for a couple grand. Pushing any more boost than 5-6 on that blower makes too much heat to be effective and a 250 would be better suited. Butt any more than the 177 you will probably need to switch for dished pistons.

 

[ram750]

I would imagine a fairly small displacement blower like that gets pretty quickly out of efficiency range ... I was not looking to make way more hp , just enough to break a personal challenge to run past the 75 mph range ! ...

Do you think I can get away with the factory fuel pump and possibly carb ? would need some new jets most likely and a box of spark plug to check the tune... I am thinking a couple degree's of timing need to come off also ... Hmmm doesn't sound to complicated Do you think I need to change the manifold for aftermarket ?

 

[Gimme Fuel]

I couldnt tell ya on the fuel pump and carb stuff. I dont mess with those. I like my EFI.

I understand most carbed boosted guys run the merc thundervolt ignition module for the v6 because of its better timing curve for boost.

What exhaust manifolds do you have now? If you have the old cast center rise manifolds, those are very restrictive and should be changed to a decent aftermarket performance manifold to get the most from your engine mods.

 

[ram750]

I have been shopping for used stuff over the last couples days ... It's slim picking up in Quebec so I craiglist the upstate NY area for Headers of Blowers....

My plan is to get Headers/Manifolds first then get myself a blower. I read and found a couple post online about guys who have done the upgrade so I have a clearer pictures of all the parts I will need.

In the mean time how much should I expect to get out of the manifolds ? Do you guys think I should by my next prop based on the extra hp that could be extracted from the headers ?