new here
 

Hi everyone I'm Rick I'm new here I'm going on 2 1/2 years now with my Mariah and love it. But now I want more speed out of it and was hoping to find some answers on how here I recently installed the triple exhaust but it gained no speed at all, hoping maybe someone can tell me what I need to do to make it pick up some more speed

Re: new here
 

What is your current speed (GPS) and rpm's at top end? What are you trying to gain; top speed or more mid range acceleration? What engine / outdrive do you have? What pitch prop is on it?

Re: new here
 

My current speed is 55 mph and my rpm is about 4000, I would like to get at least 65 mph out of it, Its got a 454 with a bravo III the props are 28 pitch I was gonna change my props but everywhere I looked had a different answer 1/2 said go smaller and the other 1/2 said said go bigger the props are about $900 so i would like to get the right size the first time just don't no which way to go smaller or bigger

Re: new here
 

Your RPM's sound like they're on the lower end of the correct range, (recommended 4200-4500) but your top speed of 55MPH sounds just right according to the 7.4L specs in the 2001 brochure. Changing your prop pitch and exhaust won't get you anywhere near 65MPH. Honestly to get the 10MPH difference you want is going to involve either upgrading engines, or supercharging. The general rule of thumb with marine engines is it takes 15 extra HP for every 1MPH gain at that speed. Supercharging will set you back a bare minimum of $5k, and would put you at about 500-550HP. Something to seriously take into account is the structural durability of these boats is only designed to support a max of 425HP, which is the 496 Mag HO engine, which retail brand new for about $16k.

As much as I hate to say it, it just might not be possible to squeeze that much out of your boat. Mariah's were built for luxury, and although they are somewhat fast, they can't compete with the specially designed speedboats such as Baja, Cigarette, Donzi, & Fountain. They're two completely different species.

Keep us updated on what you decide to do!

Re: new here
 

I was actually looking at a pro-charger and changing to some headers which is gonna be about $7000 I know its more of a luxury boat that's why I love it but I'm also a bit of a speed freak and always looking for more speed but if the hull won't handle the power what can I do to get any kind of speed gains

Re: new here
 

That's the thing that sucks about marine engines, performance accessories are so limited, and the ones that are available are either ungodly expensive, or provide little to no benefit at all. I have heard about headers being an improvement, and you might get a MPH or 2MPH out of it, but I wouldn't expect a major jump in HP. I did some research into the procharger kits a while back, and heard a few positives about it, but a majority of negatives about supercharging the 7.4L MPI. They say the engine internals are not meant to withstand anything more than the standard 310HP. So the engine has to be rebuilt with high performance parts, which isn't cheap at all. Many of the guys either ended up damaging their stock engines, or selling their kits and replacing with a 502 Mag or 496 HO. If you haven't already, check out offshoreonly.com and do some searching around the site. They're the performance offshore racing guys, so they know just about every way to maximize speed.

I was originally very into speed when I first got my boat. My friend had a 24' Baja H2X with the 502 Mag. I used to like to keep up with him, but after the first dozen times of him blowing by me at 70+MPH, I sucked it up and just realized, yep, my boat just doesn't go fast. But I always laughed when I blew by him at the fuel dock. :D He ended up selling it a year later when fuel hit $5/gallon and it was costing him around $250/day because of those 70MPH speeds. There's no doubt it's a lot of fun going fast, I completely agree with you there. It's just it usually costs a lot to get there, and if you're prepared and willing to pay the costs, then you're in good shape and it'll be a great experience!

Re: new here
 

Think I'll go with headers for now but I'm gonna wait till this winter when I park the boat to put the pro-charger