School me on 2.5's Merc's

[sam hain]

I've had a couple different engines on my bullet, but after dropping a cylinder in my 3.0 I repowered with another 2.5
I've had a '99 2.5 200 EFI on it before, but with the prices of everything sky rocketing I went back this time with a '95 2.5 XRi 200 FF block.
I've done some light research and found that the XRi motor is very close to a pro max other than the reed block using 5 petal vs 7 on the pro max and the exhaust chest is a little different.
I'm kind of a HP junkie and I'd like to know more about my newest motor and what problem issues it has that I might be able to fix before hand.

[LakeFever]

I'm in the same boat with the same motor. The FF is a good solid platform to work with. The main issue is the stock plastic cage bearings and stock ECU limit how high you can spin these up. Stock rev limit is 5800. In order to wind them up you need to replace the plastic cage bearings with steel and upgrade the rod bolts while your in there and either find someone who sells a modded ECU or get a Brucato to raise your RPM limit. Installing new reeds is a good idea while your in there. Your going to want to ditch the oil injection and run premix and do a black box delete as well. You can shave the heads for added power so long as you run the right gas for this.

Going further you can add a seven peddle reed set up, open up ports and machine the chest, add stuffers and on and on but the FF block exhaust exit is not really going to support all the big mods like this so its really up to you how far you take this vs repowering with a 260 or something like that. Eventually you hit the wall of diminishing returns $ per hp and it makes sense to move onto a better foundation than the FF for huge power. If you do get into any machine work its wise to use one of the reputable members here to do this because they know the ins and outs and the do's and don'ts and there are lots of these.

Hope this is of some help

[Whaaaaat]

The 5800 limit is not in the ecu. It's in the three timing boxes. Pull that crap off and it will spin a lot more than that. Ecu will go full rich at some point but it's well past that 5800 limit in the timing boxes.

[Dave S]

YesYes on the rod bearings...... replace w/steal...... cages......

[tlwjkw]

compression and "rod slots"......

[LakeFever]

compression and "rod slots"......

Can you explain the rod slots mod?

[tlwjkw]

look here... post #14

Mercury Tech Ported Promax build (screamandfly.com)


ya really need both (production and 225 PM, 260/280 blocks) there ta compare..

[LakeFever]

It’s hard to know how much material to take away and where without having those other blocks sitting here to compare. I’ve read that thread at least 3 times and for whatever reason never noticed the rod slot mod. Maybe I’ll smooth and gently modify those openings on my block. At least make them all symmetrical. Wish there was more pics. I’ll probably just clean and smooth everything, match sizes etc I doubt I’ll get into much porting but if I had good direction I’d probably do what I could.

[tlwjkw]

those were "Ruck's" favorite/first recommendation thing ta do ta tha block way back when...

[LakeFever]

This is a great thread on modding the exhaust chest

https://www.screamandfly.com/showthr...ight=cut+chest

[FORBESAUTO]

On the rod slot deal, hear are two different angles of a very aggressive slot opened up. I wouldn’t recommend going this far unless you are willing to fill crankcase areas to bring the volume back down after removing so much material so you don’t lose crankcase compression and velocity. The idea is to straighten out the path to the boost ports to maintain/increase flow at BDC and ABDC after the pressure has dropped in the crankcase. On the stock block the crankcase radius continues past the ports and causes the charge to have to make a u-turn to get to the ports. Normally a small amount is milled out just enough to expose the ports. Hope this helps.

[LakeFever]

I ran out of Devcon, can marine tex be used for filling the oil injection voids?

[LakeFever]

Also is the 200 plate sufficient or is it essential to get a Promax plate and open up the block to that size?

[TraceF3]

I've had a couple different engines on my bullet, but after dropping a cylinder in my 3.0 I repowered with another 2.5
I've had a '99 2.5 200 EFI on it before, but with the prices of everything sky rocketing I went back this time with a '95 2.5 XRi 200 FF block.
I've done some light research and found that the XRi motor is very close to a pro max other than the reed block using 5 petal vs 7 on the pro max and the exhaust chest is a little different.
I'm kind of a HP junkie and I'd like to know more about my newest motor and what problem issues it has that I might be able to fix before hand.

Without reading a single reply I want to say this is going to be good. There are a plethora of experts on S&F and I'm gonna read every word 'cause I got a project comin' up

[nitro_rat]

I ran out of Devcon, can marine tex be used for filling the oil injection voids?

Yes, Marine Tex is perfect for this!

Also is the 200 plate sufficient or is it essential to get a Promax plate and open up the block to that size?

You will actually have to get a set of plate gaskets for a 2.0 XR2. The exhaust dump on a pro max plate is in the water on a FF (or any other painted 2.5) block. There is enough meat in the fishing 2.5 block/plate to go to the 2.0 opening size safely. It's MUCH bigger than the 2.5 dump size!