225 Promax converted to 1 piece plate on factory 15” water pressure

[anew17]

I just put my 225 promax power head on a factory 15 with a 260 plate. I have hardly any water pressure at idle with barely any water coming out the thermostats (washer with 3/16 hole) and around 12psi @ wot 91mph. 185degrees off the head not water. I deleted the poppet to so I could run the single piece plate. My question is, is there a reason to restrict the water flow from the water outlet where the poppet was? I’m seeking more pressure at idle. I don’t think my block it’s completely full of water at idle

[rjdubiel]

OK... lots and lots of info here you just need to find it and start reading. Use Google and search in Google what you are looking for and then "Screamandfly.com" after. so for example

Promax on 260 plate "screamandfly.com"

This will bring up way more info and threads than trying to use the search bar on this site.

1. what rpm are you running and what do you plan to run max rpm? What eclectics are you running (40amp or 16 amp)? What do you have for main bearings on the crank (plastic?)? What do you have for pistons (cast/forged)?
2. Depending on your answers above, this will tell us what you need to do with the water. I would try to completely block your poppet dump hose as I suspect you are dumping a lot of water and your water temp is not as high as you want it (140-145 WATER TEMP, not head temp).

some more reading http://www.us1.cc/racingcoolingsystem.html

[Mrzip]

You won't get a lot water pressure @ idle.

[wcarlyle]

I am no expert and not sure this is your issue, but on my 225 Promax with one piece adapter plate I had to plug the dump holes in the plate and re-drill them to 17/64th so the block would hold more water.

[LakeFever]

Theres lots of info in the last few pages of this thread below

https://www.screamandfly.com/showthr...-adapter-plate

[drakeyoungx]

I’m drystacked now but i ran 3/16 dumps and open poppet and had over 30 lbs. If you want to keep pulling powerhead trying different size dumps go ahead. I had good luck with drystacking and tuning hose size. I think if you had 2 1/4 holes in plate dumping you could have around 20-22 at wot which is what you need on a steel bore single pc plate. John Marles has a write up on this aswell… My guess is that you’re running the factory dumps on the plate for a nic motor they’re like 1/2 inch. Close those up a lil and you’ll increase water pressure. Another thing you need to put diverters in the cylinders. 1/4 hose to divert water

[anew17]

Good info thank you. It’s got 4 3/16 dumps in it. Steel sleeve motor

[drakeyoungx]

Gotcha so you have 12/16ths “ total. that reduced is 3/4” dumping towards water pump. I think you should try 2x1/4” dumps which will equal 1x1/2” dump and see what your pressure does then, I was told around 22 psi running is what you need on a steel bore motor with 1 pc plate.

To simplify this…
To increase water psi, dump less
To decrease water psi, dump more
Find your water psi goal and check your temps. don’t forget to add diverters on the cylinders i’ll attach an image showing where

[tlwjkw]

he's been doin' this for a very long time....

US1 Mercury Outboard Race Engines and Top Pin Pistons

[drakeyoungx]

he's been doin' this for a very long time....

US1 Mercury Outboard Race Engines and Top Pin Pistons

Yes John has a really in depth explanation

[tlwjkw]

yes he does.. something lotsa folks don't know is tha tha production 15" pro max had a one piece plate thats different than all tha others.. it's machined to use a poppet and stats in tha motor but its like lookin' for tha unicorn............

[drakeyoungx]

yes he does.. something lotsa folks don't know is tha tha production 15" pro max had a one piece plate thats different than all tha others.. it's machined to use a poppet and stats in tha motor but its like lookin' for tha unicorn............

I personally have had good luck running 20-22 psi on a 15” mid 280 plate. 225 pro max. Runs very good and ahhhh the sound Now i’m putting together a cut steel bore 200 with a horn front, should sound really good and run hard!

[tlwjkw]

jus takes a little time n patience ta make 'em do what ya happy with..........

[drakeyoungx]

jus takes a little time n patience ta make 'em do what ya happy with..........

Thats right and that’s what this forum is for, Helping each other out. I’ve learned a lot from S&F. Just trying to keep the 2.5 alive

[anew17]

Thanks. This will be my next shot. Please attach that photo need to make sure mine is right