Force 75hp milky plugs

[250Gimp]

Hi all

We have a 1999 model year Force 75 and there is some milky stuff on the plugs, so I am looking for some help diagnosing this.

Here is what led up to me checking plugs:

Skiing the kids at WOT and on the return trip with the second teenager the engine dropped power to what felt like 2/3 or 3/4 of normal power. (No tach to confirm) Thought I was running out of gas the way it reduced power but it kept going. Skied one more light kid and then pulled in to check things out. 1/2 tank of fuel, new this spring but mixed with a little bit of stabilized fuel from last fall. Pulled plugs and all three have milky deposits, to differing degrees.

Cleaned plugs and did a short run again. Same low power and plugs had milky residue on them again.

Did compression test today and average for each Cylinder, after 3 tests, was 135,138,140 psi.

This doesn't seem like a blown head Gasket, so I ask for your help on this one.

I was wondering if it is possible for the throttle cable to slip, leading to reduced rpm? (No second person to test on the water right now) That doesn't explain the milky residue, which Reminds me of water and oil mixing.

Thanks for your help!

Cheers

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[Nordin]

Water at plugs are 4 different issues.

1. Blown head gasket
2. Bad gaskets at exhaust plate or bad exhaust plate cover.
3. Crack in water jacket.
4. Bad lower crank seal.

Start to check head gasket and then exhaust plate gaskets and cover.
Be careful when removing the bolts at exhaust cover, they snap easily.

 

[250Gimp]

Thanks Nordin

One thing I thought of since I posted....... I tested compression with th motor dead cold. Should I run it until it warms up first?

Can I remove the head to check things and reuse the gasket if all looks good?

No evidence of leakage around the exhaust plate or the head, that I can see or feel.

Cheers

 

[21BaylinerCC]

I'd check compression on an engine that has warmed up.

I wouldn't reuse the gasket... the Clymer manual states to replace it when the head is removed.

 

[250Gimp]

Thanks 21

 

[Nordin]

You can check the compression with cold engine, I always check with cold engine and the result will not give any big different.

Yes you can reuse the old head gasket if it is not bad, just tight the bolts in an circular pattern starting with the left center bolt and in CW order.
Do it in three steps, if you put a new gasket in you have to retorque after some hours of running as the new gasket will be compressed.
The old will not be compressed any more as it is used.

 

[jerryjerry05]

You said:

No evidence of leakage around the exhaust plate or the head, that I can see or feel.​

It won't leak to the outside and you'd need x-ray vision to check it.

The all 3 plugs with water is the exhaust plate gasket or the lower seal, I'd bet the gasket??.

I just bought a borescope for my S7 phone. $15

It has a 3ft+ lead for taking pics and seeing in those hard to get to places.

 

[250Gimp]

Thank so Nordin and JerryJerry. Would the blown exhaust gasket cause the loss of power as well? If I put a borescope in through the spark plug hole what am I looking for?

cheers

 

[250Gimp]

JerryJerry. You talk about the exhaust plate and I realized I was thinking of the exhaust 'port' plate. The port plate is easily accessible and the gaskets are inexpensive. The exhaust plate gasket is a lot more expensive and looks harder to install.

Can you clarify which you mean please.

Thanks

 

[Nordin]

250Gimp I am refering to #22 exhaust port plate gasket 27-8190231 and #23 exhaust port plate 1000-8192831.

During the piston travel down the cylinder bore it create a vacuum in the cylinder and if the gaskets at the exhaust plate leak water from the water jacket at the exhaust cover/exhaust plate will intrude into the cylinder.

 

[jerryjerry05]

The exhaust cover on the port side of the motor.
You'll need to drop the lower unit then put scope up the exhaust tube.
Or you can insert the scope in the piston and out the exhaust holes.
Be careful as the gunk can block the camera.

 

[250Gimp]

Thanks Nordin and Jerry. I will check it out when I am at the cottage next.