Can you install 225 ProMax Powerheads on 2.5 200 EFI Mids?

[mragu]

What if anything would need to be changed? Thanks in advance, Mike

[99jav]

You will need the 225 rpomax adapter plates or cut yours to match the 225. Everything is the same on the plates except the exhaust dump. The 225 promax is bigger.

[Jay Smith]

You will need the 225 Pro Max tuner adapter plate I DO NOT suggest trying to open that 200 adapter plate , just my opinion ....

Jay

[mragu]

Thanks Jay

[coffeeguy]

Why shouldn't the 200 adapter plate be opened?
Could it not be gasket matched?

[Jay Smith]

The 225 PM exhaust openings is huge compared to the 200 , the gaskets are completely different and IF you try to open the 200 to equals the dump area you WILL compromise the metal needed to seal gasket the gasket integrity WILL be compromised and WILL fail and draw water up 5 & 6 use the CORRECT parts folks and dodge failures !!
I am 100% for gasket matching I do it daily BUT this is something different and for 100 % successes the correct part , very cheap to do it CORRECTLY ..

PS When I build modified 200 EFI I will open the small exit no more than 10% and require the customer to send his 2 piece tuner adapter , i create a tinplate make a duplicate if the block after I open it and transfer the exact 10 % opening on his tuner adapter ( no more ) I also use the more hardy metal impregnated gaskets , never had a base gasket failure but I have witnessed 5&6 failure because of gasket integrity failure..

JMO building these things for 25 years , others can do as they please as long as they own the long term end results and not me and my business , people ask my opinion and why my opinion is what it is all I can do is respond with years of observations of succes and failure ...

Peace and good luck ,



Jay

[coffeeguy]

Are 240 or 260's the usable or is the adapter promax specific?

[Jay Smith]

I find MAJOR mismatches on intake and exhaust inlets and exits on these engines one major hidden HP robber is the divider plate , with the bare block sitting on the table attach the divider plate with 2 opposing bolts note the Horrible mid match from the down coming block to the divider plate , this can be removed with 10 minutes with dye grinder and polish with cartilage roll ...

PS I always radius ALL intake and exhaust edges any place flow moves hates sharp edges , I even radius all edges on pistons ( skirts , ports , crowns )

PS 2 I am and always been open to help any and all with problems and issues that I can with any 2.5 motors, I’ve told Cathy on many occasions when We were getting started racing outboards there was no one that would help and I was not going to allow people to struggle if I could help , everyone that calls can attest to the fact I am more and willing to talk and help with issues and if I don’t know I have resources that I can find out how to fix . I am VERY opinionated but I’m an old fart ( 66 ) and KNOW what works and what dont , what parts what vendors I’ve had 100% success with and will share my assembly technology thats worked for hundreds of successful motor builds ....

Im not an advocate of jury rigging parts to fit as I am responsible to these customers builds for the LONG haul and have to answer for my failures no matter how few they are , I’m not good taking ass eatings ( ask my wife ) so I build things with complete confidence I’ve done all with all the knowledge I’ve gathered ...

Jay

[Jay Smith]

225PM 2 piece tuner adapter attached to the 225 PM block is IMO the correct way to the addition

Jayb

[90 5.0]

What is your planned usage and rpm range?

i ran a 225 promax on a 200 adapter plate stock(not gasket matched or anything) for around 200hrs on my fishing boat.

I actually saw a slight increase in bottom end(popped up a little faster with big wheels and heavy loads).

I changed it to the correct 225 divider plate when racing it, I only saw a 400rpm increase in the 1000’.

If not racing and you don’t already have a 225 base plate, it’s not worth going and buying one imo from my testing.

If racing I’d find a one piece promax divider not the two piece anyway.

If you have a 2 piece 225 promax plate, put it on. If not don’t worry about it.