Cooling system routing

**idvette** · 08-04-2023, 07:12 PM

Hey guys. I'm working with a 2.4 175 2 piece plate, bolted up a 2.0 sst 120 motor. Been a few months since I took it apart, and didn't take any pictures. Have the mercury manual in pdf form, but don't see hose routing, plus the 2.0 is a little different, and don't want to get this wrong. The plate has a barbed fitting in the back and 2 on starter side of motor that are joined together. The 2.4 had a fitting on top of the block that had a tee inline for water pressure, then went to the back adapter plate fitting I think, can't remember. The thermostats were joined together and dumped off one side to the pisser.

The 2.0 has the top of block fitting blocked off, thermostats joined together and dumped off 1 side. Poppet hose cut.

I don't remember where the poppet valve hose went from the 2.4, currently using my old hoses the only thing it reaches is the pisser outlet, which doesn't make sense. Maybe I'm missing a tee?

I've searched the site and haven't yet found a good hose routing diagram that will work for my 2 piece mid/2.0l combo, taking into consideration the higher expected rpm range, what's going to work for me here?

TIA guys

**tlwjkw** · 08-04-2023, 10:31 PM

one or two piece adapter plate?.. i've never seen either with 2 hose bibs on tha starboard side?

**idvette** · 08-04-2023, 10:34 PM

Originally Posted by tlwjkw

one or two piece adapter plate?

2 piece plate

**tlwjkw** · 08-04-2023, 11:07 PM

that motor was made ta run ona 12"/speedy or 15" with one piece plate...like said, never seen a factory one or two piece with those type bibs.. have seen one on port side and one in tha rear but never on starboard side?.. sounds like someone has done some kinda mod to it.. may have ta do with tha poppet/no poppet situation??.. i do know that with a factory two piece ya need ta have a poppet and T-stats on tha motor.. without actually seein' it hard ta say whats goin' on there..

**OnPad** · 08-05-2023, 03:06 AM

little newer stuff (2.5). The barb on the back of the adapter goes to the thermostat hose, the pisser, tee's off between the thermostat and plate fitting.
The poppet hose goes to the top of the engine, where you got the pipe plugs. This is the hose you t into for water pressure.

Not sure about fittings on starter side? If any of my 2.5 plates have em, they're plugged off.

Old 2.4l I have, has no poppet hose.
The thermostat hose, tee's into adapter fitting on port side, and pisser.

Double thermostat pissers with a crossover on top, and some tee's lower to get some water to the plate, probably is better than either above.

**idvette** · 08-05-2023, 12:18 PM

Thanks for the replies. I found the missing tee under my workbench with some other random parts. Took the fitting out of the top of the 2.4 block and used it in the 2.0. Thermostats to pisser with tee for rear plate fitting, top of block to poppet with tee for water pressure. I'll run it tomorrow and see how it works.

**pcrussell50** · 08-05-2023, 12:44 PM

Originally Posted by OnPad

little newer stuff (2.5). The barb on the back of the adapter goes to the thermostat hose, the pisser, tee's off between the thermostat and plate fitting.
The poppet hose goes to the top of the engine, where you got the pipe plugs. This is the hose you t into for water pressure.

Not sure about fittings on starter side? If any of my 2.5 plates have em, they're plugged off.

Old 2.4l I have, has no poppet hose.
The thermostat hose, tee's into adapter fitting on port side, and pisser.

Double thermostat pissers with a crossover on top, and some tee's lower to get some water to the plate, probably is better than either above.

Notfernuthin’, but this is precisely how my late 1990 2.4/200 is. Don’t quote me but I think 1990 or so was the last year of the 2.4 family before the 2.5’s took over. So I do not feel surprised if Merc was moving the 2.0/2.4 family in that direction.

===

My 2.4/200 is like this/

1) Poppet has a barb, hose goes up to a pipe fitting on top behind the flywheel (where you attach your water pressure).

2) plate has a barb that goes aft to a tee. One end of the tee is the tell tale. The upward leg of the tee comes from the thermostats

-Peter

**tlwjkw** · 08-05-2023, 01:02 PM

does tha motor have an operational poppet and stats or open and restrictor washers?

**idvette** · 08-05-2023, 01:04 PM

Originally Posted by tlwjkw

does tha motor have an operational poppet and stats or open and restrictor washers?

It has washers in place of thermostats, I didn't take the poppet apart to confirm what's in there.

**derekfl** · 08-05-2023, 02:05 PM

maybe no help, but this is in another thread right now. no such thing as TMI. the poppet is not shown though.

**tlwjkw** · 08-05-2023, 02:21 PM

If they are tha 1/8" hole ya might wanna change 'em ta 3/8" or put 143* stats.. tha poppet will need ta be operational with tha 2 piece plate... youcan run tha hose from top of block to poppet cover if you want but really not necessary...

**FMP** · 08-05-2023, 02:36 PM

Poppet is down low , fresh inlet , starboard block.

Not sure about your 2.4/2.5 turnover year but , always assume it' opens and flows the increasing volume into the block both sides around the jugs , the exhaust plate still first inline receiving as normal but the added volume cool water going right the block.
The 1/4" hose routing up, not much at 1/8" per side final.

**Merc 2.5** · 08-08-2023, 08:29 PM

I know the 2.0 fishin motors had poppet valve that didn't have hose comin off of it, atleast not to top of block like 2.4 and 2.5 does. Sst120 prob different especially with 1 piece plate

**skialot2** · 08-08-2023, 11:54 PM

I have three 2.0 motors. a stock 135. a "Full Race" 150. and a stock 175. Both stock motors are routed the same. From the poppet to the top of the block with a tee for the water pressure gauge. Then a separate hose from the starboard thermostat to the port thermostat down to a tee. One side goes to the adaptor plate. The other side to the telltale. Both these motors, the telltale basically just dribbles. Motor runs at 140 at speed 160 when going slow. The "full Race" 150 goes from the poppet to the starboard thermostat to the port thermostat to the telltale. Adaptor plate is blocked off. Top of the block is water pressure only. Telltale sprays like a garden hose nozzle. Motor runs at 140 all the time.

**tlwjkw** · 08-09-2023, 02:06 AM

Originally Posted by Merc 2.5

I know the 2.0 fishin motors had poppet valve that didn't have hose comin off of it, atleast not to top of block like 2.4 and 2.5 does. Sst120 prob different especially with 1 piece plate

tha hose from top to poppet didn't come to production till '89 with tha water cooled reg/rec cause they were cookin' off.. it was to help rid tha system of air bubbles ta supposedly help with coolin tha reg/rec.. it was found ta be a little beneficial to tha complete coolin' system (production motors on two piece plates) so it stayed around... i've run motors ('89 up) with 16 amp stuff or tha dual reg/rec 40 amp without tha hose without any problems.....

i've never seen a hose from tha poppet tie into any t stat hose "ever"... hot rod or production.... thats tha same as runin' straight off to nowhere.........

jus curious? what defines "full race"? does it have stats/washers or neither??.. does it have poppet guts or nothing at all??

any hot rod (hi perf.) one piece plate coolin' is completely different compared ta tha production two piece stuff no mater what powerhead is on it.. but it will need an operational poppet in tha block with a two piece..