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454 mods... best bang for buck

diaster

diaster

Member
I have the 454, thought it was a magnum, doesn't look like a high rise mani to me. Anyone know the best bang for buck upgrade non efi.
ie highrise (brand)
bigger carb (ie 800 series holly)
cam or not?
 
Easy stuff would be Cam (roller is the way to go), high rise intake manifold, and performance exhaust. 800 cfm carb is a little big for mild upgrades. I wouldn't do anything to it if the engine is tired or has a lot of hours short of total rebuild.
 
Take this with a grain of salt...and maybe a little lime, since I've never modded a boat motor. That disclaimer out of the way, most of the threads I've read about modding a 454 non-mag start by telling you to look for a different motor...i.e. mag motor or the like with better internal parts that will give you a better base to start modding. Sell your existing 454 to offset the cost. Next they will say, as Jetmate, to start by rebuilding the top end if it doesn't have low hours on it. Important in that is to use better gaskets that will be able to handle the hp upgrade. Add a more aggressive cam, better exhaust, a whipple or procharger if you like. Then be prepared to shell out money for hydraulic steering for those higher speeds. All in all....lot's of $$$ if you want to see a significant mph increase. If you have the $$$ god bless you. :cheers:

With this out of the way...wait for a response from someone who has modded a motor to give you expert advice. ;)
 
I would leave what you have alone, find A rebuildable 502. Build that on the side or over the winter. When its complete drop it in over a weekend and never miss out on boating. Then take your stock engine and wrap it up and put it in the corner. Then if you ever want to sell take your new motor out and stick the stocker back in.

The big question is how many hours on your engine now and whats it in.
 
details

it is in a 1996 Persuader 235. It does 68 trimmed out with a 4 blade 24P Mirage. It has performance xhaust (captains call) and I dont know if its a magnum motor or not for sure
 
Call mercury with the serial number. They can tell you what the motor is. If that fails, call checkmate and they can look at the build sheet. That will say what the boat came with.
Those 2 options will at least help you find out which motor your dealing with :)
 
I agree with above......start building another motor on a stand if you wanna go faster. I wish I would have heeded that advice 3 years ago......
 
If the motor is a 1996, I THINK all of the mags were EFI. Not totally sure though. Both of my mag motors had BIG red stickers saying EFI MAG on them.

As mentioned if it's 68gps with a 4 blade (all mirages I've seen are 3 blade) then that's moving that boat real good for a 330hp 454 though.

I'll second Red's advice about building a hot motor. BUT if all you're doing is lightening headers and maybe a mild cam (be sure to mention your slient choice when spec'ing it) , I think a healthy non-mag motor would handle that.

I've also been toying with the idea of a small bump in the rev limiter in my mag motor - maybe to 5200 rpm. Would give a few mph increase over the stock 4950 limit and I've heard is safe on mag motors. Especially for short bursts which is all I'd ever do.
 
Non-mag bottom ends will hold up just fine to better heads, intake, exhaust, and a semi-hot cam. They will be just fine for anything 400-450 hp turning stock rpms if they are tuned properly. A nice set of rectangular GM 088 heads (easy to find used for cheap) with cleaned up ports, nice high rise rectangular port intake matched, good carb, a medium cam, and nice manifolds will be a nice budget motor.

It will not take that much HP to really increase that persuader compared to a convincor so a budget build like mentioned above will really gain on that hull.

There are plenty of people who have put nice top end kits on and have not lessened reliability. If you are going to go the boost route, then that bottom end will not be adequate.
 
thanks for all the advice... i am happy with the speed, just like the sound of a built motor more than anything. I was running the 3 blade mirage plus (25p) and didn't like the handling, more of a smooth water prop i think. Where my 24p 4 blade seems to get the bow up and on plane waaay better.
 
a set of large oval port heads, like 781's, performer RPM intake and a good roller cam will do wonders with that...
 
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