Bobs Performance accessories - what helps

[jeffbare]

I am getting a 1991 200 2.5 merc for my vegas xt. What will Bobs Machine velocity stacks, and exhoust housing do for me? My wife wants the boat to be quiet. I am looking for some small tweaks that wont ruin the everyday use factor.
Jeff

[Reaction19]

velocity stacks are a must also the cowling louvers and take the rev limiter off and the idle stabilizer off too and set your wot timing to 25degrees. as for the exhaust housing it does help a littleeeeeeeeeee bit but if your wife wants it quiet and you install this you might be sleeping in the boat. but there is nothing like the sound of a loud v6 merc at 7000. dont be afraid of turning 6500-7000 with that motor mine has 400hrs with lots of abuse at those rpm's . seems like the harder i run it the better it runs...

[jphii]

I think the best performance increase you can do is dump your wife. Mine slows my bote down more than anything!

[Reaction19]

i was trying to be nice

my wife holds on like a soldier and only complanes in heavy chop...

[Rickracer]

...a compression increase. You could get some increase by simply changing head gaskets. Bump the compression up to around 135~145 cranking compression and you will see an across the board increase in both torque and horsepower. It will not raise your RPM range however. That will require a combination of other modifications, including but not limited to: porting (both block and pistons) , velocity stacks, exhaust chest work, possibly bigger carbs , and so on. :cool:

[jeffbare]

I am running a carborated 2.5, am I wrong in understanding that the velocity stacks are for a efi motor? Reaction19, are these tweaks something I can do on my own, or do they require a mechanic. I am so so as a mechanic, but can read a manual.
Jeff

[Rickracer]

....you can find them here: http://www.rickracers.com/index.php?cPath=21_26_359 , your S&F discounted price would be $55 + shipping.
Head Gaskets here: http://www.rickracers.com/product_info.php?cPath=21_26_30_138&products_id=253 , S&F price, 25.59 each + shipping.
Boyesen Reeds here: http://www.rickracers.com/product_info.php?cPath=21_26_40_212&products_id=414 , S&F price, $139 + shipping. If you do the reeds, be sure to read the instructions and have the supplies handy to lap the reeds cages: an 8X10 piece of glass and some 180, 240, 320, 400~600 grit wet or dry sandpaper. This procedure will make your new (or even old) reeds seal much better. The Boyesens may give you a few more RPMs on top, or they may not, but they give a much better idle, and strong low and mid range snap. An even better plan would be to go to the 4 petal rubber coated cages. They flow better and seal better.

All of these can be done by a "civilian" if they are handy with a wrench and a manual. I would do the exhaust by either drilling or opening the bottom of the midsection, (like Merc does on their non-offshore high perf housing) rather than using a bolt-on exhaust housing. Much quieter off plane, plenty of exhaust relief on plane and less likely to crack and trash a mid. Skip (Talon 2.5) did a thread on this mod a while back that works excellent, and is re-sealable (for those times when you need it to be quiet). It is here: http://forums.screamandfly.com/forums/showthread.php?t=21458&highlight=Exhaust+relief .
Good luck, and if we can be of any assistance, just let us know. :cool:

[Fish]

Rick is right, as usual. I had the same motor and went through the same thoughts. Change the gaskets or cut the heads to give you 135-145 compression (any higher and you will not be able to run pump gas) and run premium gas only. Definitely best bang for the buck. If you add the velocity stacks, you will have to rejet your carbs.

Your boat is going to be really loud if you cut the mid so if wife has isues with this, you might want to think twice. I would suggest drilling 5 1/2" holes in the botom of the mid on each side (facing down towards the cav plates) if you are going to relive the exhaust, it will be quite off a plane, but it will be loud when you are up and running.

You also might want to think about solid motor mounts if you have not done so already. What Lower Unit are you running?

[pyro]

If you add the velocity stacks, you will have to rejet your carbs.

Cowl louvers may also lean out your mix if you don't re-jet correctly.

I'd say try thin head gaskets first, then cut the heads if you want more. 93 octane pump gas is safe with 145 PSI, no more.

How about a little shot of nitrous?

-Chad

[Raceman]

Other than lookin' cool, I've never seen an advantage in adding velocity stacks to a V6 Merc. In the old days of the factory high perf merc carb motors, the factory didn't use em, not even on the carbed race motors.

[Reaction19]

I Say They Work Because I Have Them And Proved It To Myself. Also I Just Relieved The Exhaust On Mine And It Make A Big Difference On The Acceleration Aspect. But I Am Running 150lbs Of Comp. With Stck Jetting And 25degrees Of Timing Velocity Stacks And Exhaust Housing With No Problem.

[hsbob]

jeff


other than shaving the heads, you must consider mods in combinations. just adding the stacks without doing something at the back end may not help much. first thing i would do is have jay cut your head [$200-250]. this helps bottom and midd range plus getting 2-3 mph if your lucky. next is propably the 1" spacer between the carb and intake [125+-].

[jeffbare]

Bob,
I am getting a new power head next week? are you still interested in my 2.4 with a hole in one cylinder wall?
Jeff

[brotherxb03]

If your running 150 psi with stack's,stock jet and not even bosen dual stage reeds to richen it up on the hill your flirting with a melt down. It will get you sooner or later.

[Reaction19]

it's been like that for two years of nothing but abuse. with no problems just good 40:1 oil. and i run it all out all the time weather permitting the longest i've been wide open is 26miles and egt and temp were on the money. i guess jay @sst knows something you guys don't about carb 2.5's.

[action20]

I am getting a 1991 200 2.5 merc for my vegas xt. What will Bobs Machine velocity stacks, and exhoust housing do for me? My wife wants the boat to be quiet. I am looking for some small tweaks that wont ruin the everyday use factor.
Jeff

sleeping in the boat !!! LOL so ....true there are loud hogged out but the do sound cool. then again maybe sleeping inside the house would be better?

[M.CHAPMAN]

stacks are a total waste of money!!!!!!!!!on a Merc V6

[jeffbare]

I am glad to hear that the stacks don't do anything, less pressure on myself to buy them. And here in the Puget Sound area it is always much nicer to be sleeping inside.

[150aintenuff]

since yer powerhead is bolted up... the bigest gain I saw with my 150 on my fissin motor was to place a 1/2" spacer on the air box cover bolts it actually would suck air through the cowl vents on top finally.. gained 200 RPM on top and idled smoother... didnt have to adjust anything.. and it cost me 3.00 for the spacers and longer mounting bolts..

ran it that way for 6 years.. and still runnng semi strong with over 3000 hrs....

[1BadAction]

if you have a clamshell cowl, dont put stacks on it if you want quiet. open carbs are the most annoying noise on the face of the planet, and the resonant frequency of the clamshell makes them even worse.

[blkmtrfan]

and still runnng semi strong with over 3000 hrs....

Nick are you saying that you have over 3000 hours on your merc 150 with it never being apart :confused:

[jeffbare]

Nick,
Do you have any pictures of the spacers once they were installed?

[150aintenuff]

Just over 3K 3045.6 it has never ben opened and this year we replaced a VR , stator, and flywheel, timing triger and resealed the gearcase 2 years ago.. it does however LOVE to eat waterpumps... 1 complete kit every year...

the motor rolled 3K hours about 2 trips after the rally... hr meter is mounted inside cowl..

[150aintenuff]

no pics of the spacer but when I install the motor o the stream I will get some for ya

[1BadAction]

its a steel bore. as long as you run decent oil in them and dont spin them more than 6500 they last forever.

the old mans XR2s mechanical hourmeter froze up at 1993 hours, and that was 10 years ago.

[150aintenuff]

that motor has never seen more than 5500.. it hits a wall at 5400.. even when i run the chopper and blow it out breaking on plane it stops at 5400.. and when it is in fissin duty 90% of time is pushin against waves and what not at about 2600-3500 rpm.. it only sees WOT when I drive it.. it is also babied by my dad and it is taken care of.. it saw the inside of a shop 1 time... took me 6 months to fix everything that they screwed up in settings and timing and what not.. ever since then (1993) i have fixed anything on it that failed.. never let us down..