1995 Force 120 Cooling flow path

[JD42]

Hi There,
I have a 1995 120 that is overheating. Can anyone explain the water pathway through the engine so I can trouble shoot the location of blockage? I had the engine running briefly on hose and thermostat housing off and had no flow out the thermostat housing. I took the leg off and have checked the impeller and it seems okay. I held a garden hose onto the bottom of the water tube (with the leg off) and I get some water running out of the bottom of the water jacket around cylinder# 4 (head is off engine) but it doesn't seem like enough. Any help would be great.

Sorry if this has been covered elsewhere.

Thank you,

 

[jerryjerry05]

Re: 1995 Force 120 Cooling flow path

Welcome.First question??? How much water pressure on the hose?
Profile? Location? Salt/fresh water?
If you have a bunch of pressure it should be that much comming out of the powerhead.
The impeller? The vanes? How much of bend in the vanes/blades?
The pump and housing, and plate.How much wear?
Running it in shallow water, can cause it to load up with sand in the exhaust jacket.
Pics?
Old impellers.They all come out in 1 piece?
Maybe someone has flow diagram??

 

[pnwboat]

Re: 1995 Force 120 Cooling flow path

The water goes up the water tube to the adapter plate that is bolted to the bottom of the block. There is a water passage in the adapter plate that feeds the water to the bottom of the block on the port side by the exhaust cover. It then travels up passages in the exhaust cover and is enters the water jacket that surrounds the cylinders at the top of the block. It then travels down the port side of the water jacket to the bottom of the block. When it reaches #4 cylinder, it goes around the bottom of #4 cylinder and back up the starboard side of the water jacket and up to the thermostat. The water then flows through the thermostat and into the top of the head. Then it flows down the head. There is an exit at the bottom of the head where the water is directed to a small passage in the block and gets dumped into the exhaust tube and out of the motor.

Here is a diagram. Disregard the pressure relief valve. This was on the earlier blocks. They did away with it because it was more trouble than it was worth. Also, the "tube" looking thing on the right side of the diagram represents the cylinder head.



Like Jerry says, the exhaust cover has some small water passages. Easy for sand and debris to clog things up there. Remove the exhaust cover and if it is clogged up, clear it up and double check you are getting adequate flow to the exhaust cover before you reassemble. Use the hose on the water tube like you did before. Water should pour out at the bottom of the exhaust cavity. If you do get good flow, reassemble the exhaust cover and test again with the thermostat and thermostat housing off. You should get water pouring out of the thermostat housing. If so, then you should be good to go.

NOTE: The exhaust cover has 1/4" 20 bolts. It's not uncommon for them to get corroded and stuck. Use caution when removing them. Easy to snap them off. Then you're faced with having to drill the broken bolt out. Use some penetrating oil, lightly tap, or heat up with a propane torch if you have one that doesn't want to come out.

 

[JD42]

Re: 1995 Force 120 Cooling flow path

Hi Guys,
Thank you for your replies. This is a freshwater motor but has seen lots of shallow water and sand in the last year. Impeller is one year old and looks good as far as I can tell. I did pull the ex. plate off and there was a melted gasket on cylinder #1 and #2 but no debris. Tested again with hose and have good water flow to this point. Would this melted gasket cause water on the plugs/ in the cylinders? That was the root cause of this tear down.

I had pictured the water flow opposite to what you explained. Thanks again for all your help. I will post if I ever get this thing running again .

Cheers,

 

[Inciderboy]

Re: 1995 Force 120 Cooling flow path

Hi I've been having similar problems, on a 1989 force 125hp 4 cylinder engine, I suspected the impellor etc to start and found that the thermostat had been removed, but very little water flowing out of the exhaust etc. Eventually took the exhaust cover and head off and found quite a bit of sand and silt in the bottom of all the chambers, but more importantly on my engine the blanking off between the cylinders is not solid aluminium but has rubber type tubes implanted between the casting ways between the cylinders.
I'm not sure if they were the originals as the engine showed signs of rebuild in the past, but the thing was these tubes had slipped past the baffles supposed to keep them in place and were now blocking the flow up the right hand side of the cylinders - no wonder I was getting overheating!
I am now in the process of rebuilding and waiting for gaskets etc from the US, but cannot find replacement tubes. so I'm going to improvise... I'll let you know how it goes.
See pictures of the head how it's supposed to be:
Oh ignore the marks on the pistons - that's not my engine just borrowed the pics as they show how the tubes are supposed to be!

 

[Guzzibob]

Re: 1995 Force 120 Cooling flow path

Hi Guys : New member so if I sound like a newbe I am.
I have a 1997 75 hp Force, just resealed the lower unit and replaced the water pump. My question is I seem to have good water flow out the exhaust but hardly any out the pee tube @ idle . If I raise the rpm then I get flow from the pee tube but not high pressure. I checked the therostat , seems to be ok. Is there a bypass valve that may be stuck open ?
I did connect a garden hose directly to the water supply tube ( with lower unit off ) and got the same results. Thoughts ?

 

[jerryjerry05]

Re: 1995 Force 120 Cooling flow path

Guzzi, you should start your own thread.
Include,serial#s(if you have them)
Fill out the profile,location?

There should be no bypass in your motor.
If you hooked a hose direct?? Then you have a blockage somewhere??
The old impeller?did it come out in 1 piece or pieces?
The exhaust plate might be clogged?