Another Mercury cooling question..

**A-train-97** · 09-09-2020, 08:21 PM

Anyone know if running h2o diverters in block would cause issues with building heat? Only asking cuz I was told that this might be causing the cooling issue that I'm seeing.
Here is my setup.
Steal Sleeve NN block with 5 petal front. laser injection.
Diverters installed on 3&5 @ 11 oclock & @ 2 oclock on 4&6.
Two piece adaptor plate on 2.4 mid with new 143 Deg stats & rebuilt poppet.
Rebuilt water pump with new housing and impeller.
Wet sender installed on top of Starboard head before stat.
Brand new Gaffrig temp gauge.

Testing in aprox 60/70 Degree water I'm Only able get heat up to 130/140 Deg when idling. Anything over 2g on my tach and temp drops below 100 deg on gauge. ( laser temp gun showing around 108-110 deg F when shooting top of heads ) Stats did open and dump on hose in driveway but on last lake test I never seen them open. Even when idling. Water pressure gauge at idle showing 9/10 Psi & 18/20 psi @ 5000 rpms. Pretty sure I can see poppet open and close around 12 psi on gauge. Pulled powerhead to double check everything on the adaptor along with the cowl plate but no dice. All looks like it should, no cracks or corrosion to cause leaking into mid.

I was always under the impression that jacket diverters help transfer the heat around the whole cylinder by slowing the flow. It seems like I'm seeing the opposite effects with my fresh rebuild. I've been doing a lot of searching here regarding temp problems and few and far between ever follow up with what they had found & you're left hanging with no definitive answers. Also have studied water flow diagram several times.

General advise is that steel sleeve motors need heat. Not hot but somewhere between 140 to 160 ish to live & that's why I'm concerned with my temps. I'm aware that wet temps will be off a bit compared to head temps but this temp swing seems like more than 20/30 deg. Anyone have part number for head temp sender that would work with Gaffrig temp gauge?
I could always go with Greg Moss 2pc drystack mod and regulate temp & flow with hose bibs but the ones who know these motors best say " that's not necessary cuz the stock setup works real well on steel sleeve motors."

Any advise or help will be greatly appreciated.

**nitro_rat** · 09-09-2020, 09:24 PM

New thermostats? If you got the OMC style stats that will cause a problem. Merc stats are "inverted flow" type.

**A-train-97** · 09-09-2020, 10:36 PM

Thanks for the reply. I purchased the t-stat kit from Pro Marine part number 75692Q2. The part # matches the inverted ones they list but with Q2 at the end. I figured that’s because it’s a kit & not individual.

**Baker343** · 09-10-2020, 01:23 AM

Originally Posted by A-train-97

Anyone know if running h2o diverters in block would cause issues with building heat? Only asking cuz I was told that this might be causing the cooling issue that I'm seeing.
Here is my setup.
Steal Sleeve NN block with 5 petal front. laser injection.
Diverters installed on 3&5 @ 11 oclock & @ 2 oclock on 4&6.
Two piece adaptor plate on 2.4 mid with new 143 Deg stats & rebuilt poppet.
Rebuilt water pump with new housing and impeller.
Wet sender installed on top of Starboard head before stat.
Brand new Gaffrig temp gauge.

Testing in aprox 60/70 Degree water I'm Only able get heat up to 130/140 Deg when idling. Anything over 2g on my tach and temp drops below 100 deg on gauge. ( laser temp gun showing around 108-110 deg F when shooting top of heads ) Stats did open and dump on hose in driveway but on last lake test I never seen them open. Even when idling. Water pressure gauge at idle showing 9/10 Psi & 18/20 psi @ 5000 rpms. Pretty sure I can see poppet open and close around 12 psi on gauge. Pulled powerhead to double check everything on the adaptor along with the cowl plate but no dice. All looks like it should, no cracks or corrosion to cause leaking into mid.

I was always under the impression that jacket diverters help transfer the heat around the whole cylinder by slowing the flow. It seems like I'm seeing the opposite effects with my fresh rebuild. I've been doing a lot of searching here regarding temp problems and few and far between ever follow up with what they had found & you're left hanging with no definitive answers. Also have studied water flow diagram several times.

General advise is that steel sleeve motors need heat. Not hot but somewhere between 140 to 160 ish to live & that's why I'm concerned with my temps. I'm aware that wet temps will be off a bit compared to head temps but this temp swing seems like more than 20/30 deg. Anyone have part number for head temp sender that would work with Gaffrig temp gauge?
I could always go with Greg Moss 2pc drystack mod and regulate temp & flow with hose bibs but the ones who know these motors best say " that's not necessary cuz the stock setup works real well on steel sleeve motors."

Any advise or help will be greatly appreciated.

Not totally sure on this one but why are you running deverters on what appears to be a stock 200 with a two piece exhaust plate stats and a poppet

**PanRonnie** · 09-10-2020, 02:47 AM

do you have the water bleed off installed from the top of the block to the poppet cover!?
if not it might be an idea to install it with a valve in between
this way you can regulate the bleed off
the diverters seem to be installed on the 200 xs block
i am in the same process and will order the 200xs springs see how they compare with pressure against the stock springs and decide which route to take

**Merc 2.5** · 09-10-2020, 06:27 AM

Im with baker , the diverters were meant for aluminum coated cyl with 1 piece exhaust plates, they need the extra cooling to run 8k rpm for long time , a stock 2 piece exhaust with steel sleeve didnt run them, then again sounds like if u swap stats to washers with little smaller hole then it will heat up little more. Just a thought

**bayman96** · 09-10-2020, 07:17 AM

if you have diverters, pull the thermostats out and buy the factory mercury washers that go in there place. theres 2 sizes i forget which i have. that will increase flow velocity through the block, hence decreasing the heat transfer within the water jacket, bringing your temps up. also when doing this, try and find, or make a poppet dump, and remove the poppet valve when you make the dump. before you remove the poppet test and see water temps because if the water flows too fast then it will get hot.

my cooling setup on my steelies is as follows: diverters placed as stated above, washers in tstat housing, and poppet removed.
Water hose routing: starboard head, port head, out the cowl. Poppet cover to out the cowl.

i also have a 280 midplate that is dry stacked, ended up having to restrict those dumps, as well as depending on the time of year and outside temps, sometimes block off the poppet valve.

**bayman96** · 09-10-2020, 07:21 AM

also as everyone else stated, the stock option is possibly the better route. unless you are turning 7k+ consistent, i was turning between 7500 and 8k every time out thats why i have my setup as it is

**FUJIMO** · 09-10-2020, 07:50 AM

Originally Posted by A-train-97

Thanks for the reply. I purchased the t-stat kit from Pro Marine part number 75692Q2. The part # matches the inverted ones they list but with Q2 at the end. I figured that’s because it’s a kit & not individual.

...Whenever there is a "Q'' near the end of a Mercury part number, it simply means that it is a QuickSilver Accessories replacement service part number, rather than the original Mercury part number, which is usually the exact same part number, just without the "Q" near the end. Thats all. No difference in the part itself usually.

**PanRonnie** · 09-10-2020, 08:49 AM

I have not seen it Mentioned here, but the diverters on the 200xs have a different lenght for the particular spot

**KIRCHNER** · 09-10-2020, 04:03 PM

I have read diverters should be 1/4 short of bottoming out, and a 1/4 '' below deck. race app only.?

**A-train-97** · 09-10-2020, 06:56 PM

Baker343 & Merc 2.5,
Just thought that putting diverters in would help even the heat transfer around cylinders.That's the only reason why I put them in when I had the heads off. AM I mistaken?
But it kinda makes sense that they necessarily arent needed if using t-stats & poppet. Maybe they are creating just enough resistance (ie: pressure) and the poppet is dumping to soon?

PanRonnie,
I have the hose from bleed off on top of block down to poppet hooked up. Intrestingly enough when we plugged that hose off it actually got colder. This was just for trial and error and I plumbed it back to top of block. So I don't see an advantage putting a ball valve in line with that hose. Now if it would help with the poppet dumping down into the mid then yes I think that would work. Unless my thiniking is completly screwed up But thanks for the sugestion.

Bayman96 & Merc 2.5,
Intresting statment about installing restrictors insted of t-stats & that should increase my temps. Sounds like you'er forgetting Im taking temp reading with a wet sender & not off of head temp sender. Head temp makes more sense with your statment but than again I'm easily confused at this point. I know thats how they run with a one piece adaptor or if dry stacked but I'd really prefer not to go this route unless it's my last option. My limitor is set to 7000 R's & I dont plan on hitting it very offten.
By increasing volocity & decreasing the heat transfer, I would think I'd be reading even more cooler temps with a wet gauge. I'm also going to put my dump hoses back to factory routing again. Starbord side to port side then tee & run one out bottom of cowl & other into adaptor. I had it this way but with all the jacking around the other day I switched it so they both would dump out the bottom of the cowl.

FUJIMO,
Thanks for the explanation on the parts number thing. Good to know for future use.

Kirchner,
That is correct. Diverters should be installed 1/4" short below and on top.

As of right now my thoughts are maybe its just best to pull the heads and take the diverters out. If that dosent work then I'll try pulling the poppet, install a diffrent poppet cover, run restricted dump hose off that & dump off water with 1/8" hole in the washers where thermostats go. Only thing with that is I'm not sure if I'll have to fill in the one dump hole in the adaptor plate with epoxy in order for that to work?
I'll update with my findings after testing.
Thanks again for everyones help.

**Merc 2.5** · 09-10-2020, 07:09 PM

Well i could be way off on this . If u have steel /iron sleeve motor turnin 7k rpm or less then u do not need diverters. The 200xs was its own kind. Idk bout those. I have a 7k rpm steel sleeve that I run 2 piece plate ,stats,poppet with 0 cooling issues. The diverters help keep it cool but alot times those temps r controlled by the washers not the stats in those setups. I hope this makes sense. Either get washers and experiment with those till u get proper temp or take diverters out and go with stock cooling. There's many ways to covert the cooling system but all depends on what ur doing with the motor

**PanRonnie** · 09-10-2020, 11:24 PM

I would argue that the diverters help to direkt water around the sleeve
Especially around the bottom cylinders this would be important
As i understand it the cooling water comes up to the top off the block
The enters the exhaust divider plate to stream down
Then enters the space around the sleeves through the holes next to cylinders 3'4'5 and 6
Blocking the bleed off from the top of the block would force more water around the sleeves and thus cooler temperatures as described
That's why i Mentioned it if it was installed? and possible putting a ball valve in
The xs has 62 celcius thermo stats i like the idea of the idea of the washers bleeding air to prevent steam pockets

**tlwjkw** · 09-11-2020, 03:02 AM

diverters will help in any block, any adapter combination.. merc started makin' 'em standard in tha pro max (maybe '96/'97?) for that reason.. jus something i recently learned.. i ran them in everything i built back when..... 2.4's/xr4/xr6/2.5 steel/2.5 nic, one piece, two piece, stats, no stats, washers, poppet, no poppet... any comb. you can think of... didn't mater............ jmo.