Sparkplug reading

[The Force power]

These are out of '90 Force 90 HP
The bottom (#3) Sparkplug has more carbon built-up then these others, could the be caused by the recirculation-hoses to #3 getting plugged OR intermitted spark?

 

[las]

I think these plugs are hard to read vs normal plugs. But what's the problem with the engine?
Could it be that number 3 have been hotter allowing for the carbon to stick?
Guess you'll have to wait for the experts to chime inn.

 

[jerryjerry05]

I don't really see anything wrong with any of them.
Now if one was white from heat? or one oil soaked? or light brown?
Then I might have something to say.
Where are the air screws set? They're supposed to be set at 1 turn out and left there. But some motors just don't run right at that setting???
My twin 88/85s ran good at that setting and maybe a bit more??
One customers didn't run right unless it was at 3 full turns out. Noting wrong with anything, just ran better at 3.
You do a lot of ideling?/ Trolling?
Is the thermostat still in there? Whats the temp for the thermo?
Do the starting fluid test. Results?

 

[racerone]

Heat of combustion is what makes plugs look toasty brown ( normal ) and if a cylinder runs " cool " Plugs will be oily and black.-----A compression test is step #1 in trouble shooting.

 

[The Force power]

I don't really see anything wrong with any of them.
Now if one was white from heat? or one oil soaked? or light brown?
Then I might have something to say.
Where are the air screws set? They're supposed to be set at 1 turn out and left there. But some motors just don't run right at that setting???
My twin 88/85s ran good at that setting and maybe a bit more??
One customers didn't run right unless it was at 3 full turns out. Noting wrong with anything, just ran better at 3.
You do a lot of ideling?/ Trolling?
Is the thermostat still in there? Whats the temp for the thermo?
Do the starting fluid test. Results?

Hi jerry,
Thanks for chiming in,
The reason I asked is because I parked my boat boat for the season at camp (Ontario, Canada) and pulled the LU for milky oil but that's another story
- The Set-screws are all set at 1 turn out and she's been running flawless for 3 years on it.
- I don't do much trolling mostly towing tubes
- Yes the thermostat is still in and working around 190 F.
So is there a possibility that the side-gasket is blown on #3 and is running hotter/leaner?

 

[The Force power]

Heat of combustion is what makes plugs look toasty brown ( normal ) and if a cylinder runs " cool " Plugs will be oily and black.-----A compression test is step #1 in trouble shooting.

Hi raceone,
Thanks for tuning in, what would be the reason for the different on each plug? (meaning more carbon build-up one more then the other)
Normally I would check the compression but I'm getting 5600 rpms alone in the boat and 5000+ with two and towing a tube so I'm not too concerned about that right now. however.... I will check next year before launching her back in the water

 

[racerone]

???----Different temperatures in the cylinders.

 

[jerryjerry05]

Like I said I don't see anything wrong with them.
Do the starting fluid test and see if the motor runs different.

 

[The Force power]

Like I said I don't see anything wrong with them.
Do the starting fluid test and see if the motor runs different.

Good to know & I will in the spring inspect the gaskets.
I like these motors (own 3 ) and like to keep them in good shape

 

[WinnerCougar74]

Here are some plugs I ran for about 15 hours in a 1974 135hp.
Left to right 4-3-2-1

 

[jerryjerry05]

Cougar: nothing wrong there