I got low water pressure on my 2.5L 225hp mariner. No water coming out of hose for top of block at idle. I found 2 holes in bottom of what I reckon is the exhaust plate. One on left side has restrictor in it nothing in hole on right side. When I put hose pipe to pick up tube and plug off hole with no restrictor I have water coming out of all 4 discharge hoses. My question is does the hole need to be plugged or restricted? I have pictures but can't upload them. Says there too big or something.
2011 21xrd
2011 250 Pro XS
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Will need to see a picture of the "restrictors or plugs".
When was the WATER PUMP replaced?
ANYTIME you experience problems with water pressure or overheating, ALWAYS, ALWAYS start AT THE SOURCE: The Water Pump.
ALL 3 gaskets MUST be replaced, too.
Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
Still consider myself a "Marine Apprentice" after 47 years (learn something new every day).
Mercury Parts, Mercury Outboards, Smartcraft & Accessories, Injector Service, TDR Reeds- BBC Sponsor
It was replaced last week. Having trouble getting pictures to post here. There on my phone and I can't find out how to resize them.
2011 21xrd
2011 250 Pro XS
0D181889 is serial #. Original power head was swapped out for re built specked 225 promax power head due to cost of getting cylinders re plated.
2011 21xrd
2011 250 Pro XS
That's fine- but we will likely need some pictures to determine what you have, where things have been run, and where your problems might be.
Just to confirm- how many gaskets (total) did you replace when you replaced the water pump? Did you use an OEM Mercury Water Pump Kit?
What are your current water pressures (Idle and if safely possible, WOT).
Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
Still consider myself a "Marine Apprentice" after 47 years (learn something new every day).
Mercury Parts, Mercury Outboards, Smartcraft & Accessories, Injector Service, TDR Reeds- BBC Sponsor
I used the 2 paper gaskets and the 1 plate. It was not from mercury, I got the kit from my local repair shop. I had no reading on my gauge at idle but water coming out of 3 of the 4 discharge lines and 11psi WOT. After finding the un restricted water hole in the exhaust plate and restricting it I currently have no reading on my water gauge but steady stream out of all 4 discharge lines now and 21-22psi WOT.
Still having trouble posting pictures. I transferred then off my phone onto desktop and still can't find how to resize them to the size required to post. I'll keep trying to get them up
2011 21xrd
2011 250 Pro XS
22 psi is real high for a 2.5, what L/u do you have ? I've seen all kinds of water press. Concoctions over the years, but you need to verify if you have a 1 or 2 pc. Adapter/exhaust plate , and if you have 2 properly operating merc T stats. Sounds like you had a chrome or nicasil bore motor on that mid b4, when you mentioned old one was too expensive to reline. The promax has a different 2 pc. Adapter plate than 200 or 2.4's. Most ppl. Know the exhaust part is opened up, but there is also 4 1/8 " drain holes drilled in the bottom plate to route/drain water.that fishin motors dont have, you need to ID whatcha' got.
^^^^ Good Advice.
Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
Still consider myself a "Marine Apprentice" after 47 years (learn something new every day).
Mercury Parts, Mercury Outboards, Smartcraft & Accessories, Injector Service, TDR Reeds- BBC Sponsor
1 piece plate. 4 hole CLE lower. Nicasil bore prior. And yes the holes im asking about, there are only 2 and they are 5/16". I have not replaced t stats yet. I will try again to resize and get photos posted
2011 21xrd
2011 250 Pro XS
there is your problem right there,,you should be running the proper 2 pc. promax adapter plate with T-stats,you can run a 1 pc. plate on a steel bored block,but you need to know how to run the water routing,and drainage, and where to restrict flow,to keep enuff heat in the block. the 1 pc. plate is designed to cool nicasil bores,@ high rpm's.Much safer and easier to find a promax 2 pc. plate.Originally Posted by cn8165
also,if that is a 245/260 bass mid,you will need the 225 promax exh. tuner,the 260 is too long,if it is a 2.4 bridgeport mid,then you can use that tuner,it is a good replacement for the 2.5 225
Before the rebuild it was a 245. As far As I can tell at that point it was all stock mid, foot, single stage trim. It woulda as some of the exhaust has been removed. It is also a carb motor. Non EFI. Can you tell me what this tuner does?
2011 21xrd
2011 250 Pro XS
Most of those came with a bass mid,factory drilled exhaust reliefs,and an offshore clamp,CLE gearcase,all that stuff is ok for a promax,'cept the 1 pc. adapter plate., 245/260 used a longer tuner,than a short promax,2.4 bridgeport tuner. 245 used a nica sil cylinder bore,and revs alot higher than a promax,,you need the 2 pc. adapter plate,to get your cooling under control. You may also run into a 3/4" water tube,and have to change back to a 1/2" to fit the 2 pc. adapter plate,the 240/260 block also has no provision for a poppet valve,which the promax does,,part of your current issues. the 2 pc. plate will let you route water thru the poppet correctly,,in a race block that water just runs steady thru the poppet area,and is only slowed down by washers with 1/8" holes,placed under each T-stat housing.
you may also run into an issue when replacing the 1pc plate with a 2pc. plate,,the 3 rear retaining bolts/studs ,are 1 size bigger than a std. 200 mid, the 2pc. uses 3/8" bolts,whereas the 245/260 bass and offshore mid use 1 size larger than 3/8",so you will need longer studs, for those 3 rear studs,and ream the 3 holes, on the rear ,top plate of the 2 pc. plate,for them to fit. It sounds complicated,,but will be obvious,when you get to it. also will need a 1/2" water tube,and a 1/2" outlet on the water pump outlet,on the CLE. the 245/260 pan and cowling will work fine, as will a later style alien cowl. I have a bunch of pics somewhere,of changing a ridgeback offshore mid,from 1pc. to 2 pc. somewhere, you will also lose the solid top mounts,so,adding a set of bruster solid mounts into the 2 pc. plate is recommended,,should already have factory solids in the lower end. those covers on the lower mounts are made of solid aluminum,not plastic,like the fishin motors,so,dont lose them. Also make sure you use the thick merc racing gaskets on the adapter plate,and 1 between pan and adapter plate,and 1 between powerhead and top of pan plate,or you will fill the pan with water,,and have to pull the PH again.
Last edited by cajunrgfm; 03-04-2018 at 07:58 AM.
Download a photo and picture resizer App on your phone. It's free and works great!
the one pc. plate has dump holes,yes,,but the 200 and 225pmax plate have different dumps,,pmax has 4, 1/8" holes,side by side,it was factory modified,for that motor,problem with the 1 pc. plate,is it dumps too much water, too fast,and wont let the 225pmax block warm up enuff to operate,it is common to cold seize them, running your setup w/out t-stats and a poppet valve,
2011 21xrd
2011 250 Pro XS
I agree- you will be much better off to locate a 2pc Adapter Plate, and the correct tuner. Much simpler (and quite dependable) cooling.
Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
Still consider myself a "Marine Apprentice" after 47 years (learn something new every day).
Mercury Parts, Mercury Outboards, Smartcraft & Accessories, Injector Service, TDR Reeds- BBC Sponsor
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