Force 9.9 overheat multiple causes

[cannonmaneh]

I have a 1992 Force 9.9 short shaft. Got it from an old boss that abused the hell out of it and overheated it so many times it actually melted the starter housing into the block. I put a new water pump and head gasket and the beast started but would overheat. I pulled out and tossed the clogged thermostat and the motor ran well with significant hard use for 10 years plus. This spring it started overheating again, spitting steam out the back port where the thermostat was. I replaced the whole water pump, same issue. It starts fine runs like a champ but after 10 minutes or so, spitting steam then overheats, bogs and will not run. Pull the cover and water boils on the cylinders. Pulled the lower end off and the new water pump is fine. Then pulled the power head. 6 bolts some wires, primer hose and choke and what a surprise there was in the leg exhaust. Some rubber corruption had been put in there to support the thermostat and over time it ages and swells up like some cancerous growth. It will pass water when cold, but when it heats up it pretty much plugs the water exit. Damn thing is near 4 inches long, 1 wide and 3/4 deep. With much cursing and the like I cut and wrestled it out and tossed it too. I am waiting on some gaskets for the exhaust manifold as I pulled it to have a look. Pristine. I expect it to run as it did and will try to post results.

 

[gm280]

cannonmaneh, :welcome: to iboats. We like new iboaters to join us...

I am not familiar with your engine, but before removing things, do some research to see if they used some water passage deverters to channel the water through the block and head. If there was some type rubbery plug in there, it didn't get there my itself. So make certain it was installed for proper water flow before buttoning up that head. You can go to boats dot net and research a complete break down of your engine and see if there is such a part supposed to be there. If so, buy that part and replace it. JMHO.

 

[jerryjerry05]

Yes Welcome,
If the motors had real hard use???
Then the cooling passages could be blocked with crud and not cooling???
Post a location in your signature and we'll know if it's salt or fresh water.

 

[cannonmaneh]

Update on the Force being back in the water. Many thanks for the feedback guys! Egg on face here, I cannot apparently read a sticker on the side of the motor. It is a 1997 (it was at the cottage and I was.... not). So hard use you ask. Well yes! My old boss was not pleasant to it. The main problem was the thermostat the size of your thumbnail in the port on the exhaust leg. If the motor inhaled anything it had a very good chance of gumming up the works and the motor would boil off and overheat then seize, which he did many times. What is amazing is that after all these years and many overheat seizes (boss) before I pulled and tossed the thermostat and then a couple of near siezes recently when the rubber plug/channel in the leg (completely separate from the power head) heated and occluded water exit, the motor is ok! I pulled the exhaust header and the pistons look to be in good shape, not much crud in there either. New gaskets and water pump. I then removed all the rubber crap that was put in the leg by force/mercury to house the now expurgated thermostat and it has absolutely fixed all the overheating issues. Good water flow on first pull to last hour of running with no rate change. I will not be running it late or early season so shock cooling should not be an issue. Pushing a heavily or lightly loaded Alumacraft 14 footer, no problems.

Sorry for the newbie anonymity
Ottawa Canada. All fresh water and only used 8 months of the year max. Water is too stiff the rest of the year.

4hp 1978 Evenrude destined for my 17 ft Grumman double ender.
20 hp 70s Merc on a 14 ft Alumacraft
92 Seadoo XP smiles per gallon lake annoyance.
04 5.0 litre 220 hp Volvo Penta on a Four Winns Horizon 200
Old Merc 9.8 110 on rebuild
97 9.9 Force, spare
Aquaskipper and windsurfer

 

[NLBNPB]

I have the same prob with 9.9. Rubber "grommet" swollen. Anyone know the reason this part "needs" to be installed? Possible to remove it without removing the power head? Thanks for any thoughts or help.

 

[jerryjerry05]

9.9 what? Year?
More info?
​What grommet?

If it's the water line sleeve or grommet?
​You will need this in there.
​If it's not there you can possibly overheat.
​Drop the drive, pull the water line/tube and get a set of magic fingers and reach up in there and try to pull it out.
​If you destroy it?? then try finding a new one? e-bay?

 

[NLBNPB]

Thanks for the reply. 1996 9.9 Force. This grommet is in the water discharge side of the system. The water tube coming from the pump is fine, and air moves freely now thru the system. I had the same problem as post from the fellow from Canada. Steam would exit from the discharge because the grommet was swollen and water not moving. (impeller even got hot and hub started to melt.) I'm in FL, Feel ok running W/o thermostat in warm Gulfstream. Appreciate any other information you have. Best/NB

 

[jerryjerry05]

Some of the older 9.9 and 15's didn't have a thermo.
You should be ok with that.

 

[GA_Boater]

Thanks for the reply. 1996 9.9 Force. This grommet is in the water discharge side of the system. The water tube coming from the pump is fine, and air moves freely now thru the system. I had the same problem as post from the fellow from Canada. Steam would exit from the discharge because the grommet was swollen and water not moving. (impeller even got hot and hub started to melt.) I'm in FL, Feel ok running W/o thermostat in warm Gulfstream. Appreciate any other information you have. Best/NB

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