High speed glazing

StAugJonboat

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The two plugs you show are not the same. One (newer looking one) looks like a long reach, while the used one is short. I hope there was not issues with piston hits. IDK.
the used plug was listed on marineengines.com, the new plug was listed on crowleymarine and other sites like dingbat posted ... not sure the conflict... one is not right though...
 

gm280

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the used plug was listed on marineengines.com, the new plug was listed on crowleymarine and other sites like dingbat posted ... not sure the conflict... one is not right though...

Yeah I hear you. Kind of like having one clock, you always know what time it is. But two clocks you never really know for sure...
 

dingbat

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So here's a plug a pulled out a few weeks ago. Probably run fire about 2 hours, cleaned with seafoam and than for another hour..
Your plug has a lot of carbon buildup for running just 2 hours.

The plug on the left has 80+ hours on it. The plugs on the left 6-8 hours.

When was the last time your motor was decarbed?

fetch
 

StAugJonboat

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Your plug has a lot of carbon buildup for running just 2 hours.

The plug on the left has 80+ hours on it. The plugs on the left 6-8 hours.

When was the last time your motor was decarbed?

fetch

I couldn't tell you... the guy I bought it from had it fully "serviced" about 5 months ago... not sure what that entailed. I did run some seafoam straight in the carburetor and put about half a can in a full tank...
 
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StAugJonboat

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Update... decarbonized the motor, new correct plug, ran great!!! Too great... over heated, fouled the plug and left me paddling... probably worn impeller. I was hauling a$$ though!!! 5hp on a 12 Jon boat, didn't know I could go that fast...
 

Sea Rider

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Some issues :

Is that outboard used on fresh or salt water ?

Was lightly, medium or heavily used.

If used in salt water, was it conveniently flushed with fresh water after its use ?

You need to install the spark plug that factory states as all plugs have different temp ranges if compared between them. You could screw severely any OB by not running it with a proper heat range spark plug.

Other issues to consider : 2 strokes OB's doesn't like running at low rpm for long time periods, will tend to foul spark plugs as the tip temp will not be able to reach its self cleaning temp achieved at much higher rpm range. Trolling is the worst of all the pm range for them.

All portable OB's are factory deliverd with medium pitch props. Powering a large boat with such props could produce an engine overheat due to OB is running at the min or way under min wot rpm range and you don't know anything about it. Running an OB at max throttle does not means that's running proped right..

So if plan boating while powering your 5 HP-OB will need to install an induction TT or Hardline tach and go from there for a prop maximization in order to pull wot revs at least middle to max rpm range factory stated as usually loaded, if lightly much better for the OB.

Happy Boating
 
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StAugJonboat

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It was running at full throttle for about 25 minutes, salt water. Finished with fresh every run. As far as the plug, there are two stated from different sources, look back at dingbat and my posts....I would say given the condition of the motor, it's been lightly used, it's a 96/97 mercury gamefisher
 

Sea Rider

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Better check directly with Mercury which is the correct plug. I see 2 different spark plugs a cold and a hot one. Get the correct plug, install it well gaped to specs and check if OB still overheats when in demand of higher rpm.

Flushing with fresh water any OB soon after was used in salt water is no indication that has all the water passages free of salt layers, crusts. Water will not be able to dissipate fast the heat building up inside powerhead and at higher revs OB will tend to overheat. If it's highly salted and thinking installing a new water pump will cure it, that simply won't happen..

Happy Boating
 

Sea Rider

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Thanks!!!

Which is the serial number of that 5 HP-OB, That model could be US, Belgium or Japan made. With serial number will be able to check which version is it and the recommended spark plug range.

Is your OB exact same as this one ?

P1160354.JPG
P1160355.JPG
P1160413.JPG

Happy Boating
 

StAugJonboat

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Dec 4, 2018
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I don't have it on hand, but the motor is definitely different...I have the 3 gallon external tank...
 

StAugJonboat

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Dec 4, 2018
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So, I ran the boat for about 3 hours last week, ran perfect. Checked my plug today... had a white waxy build up on the ceramic and metal contacts, put in a fresh plug, bogged down at anything over half throttle when I took it out today... any suggestions?
 
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