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Spark plugs for a mid-80s Merc XD

S

Splaker

New member
Hello folks,

First time poster! I recently bought a 16' fishing boat paired with a mid-80s 18HP Mercury XD. The seller believes it is a 1985. I still need to confirm this. But when I googled images of 85 Mercs, they look the same. Motor is idling rough and stalling while in neutral. I am going through the process of diagnosing the problem. I figured I change out the plugs while I am at it (the old ones were fouled) and lower unit oil. I am thinking a carb clean could help. While in forward or reverse, it seems to be okay, although I've only done this in a bucket, not on the lake.

What are the proper plugs for this motor? The old ones in the motor are NGK BUHW however I cannot find these plugs at my local stores. I looked up plugs that are compatible and one site listed the Champion L77JC4. Will these plugs work?

Also, what fuel filter (part/number) does this engine take?

Thanks so much in advance!
 
So it has the copper / bronze colored decals ?-----Start with a compression test.----Post the numbers here.-----And it will need a new water pump impeller.-----Most of those I look at have an impeller that is old and cracked.
 
racerone said:
So it has the copper / bronze colored decals ?-----Start with a compression test.----Post the numbers here.-----And it will need a new water pump impeller.-----Most of those I look at have an impeller that is old and cracked.
Click to expand...


Okay, thanks. It is pumping water pretty nicely... but he told me he hasn't replaced it. I don't think I have the tools to test compression, but I may.. I will look. If i don't I'll get my hands on one. Never done one before - Youtube is my friend I guess. I'll take a pic of the motor. That should confirm vintage.

As for impeller, i'll need to find a dealer who sells them. Do you know the part number for that impeller?

Thanks!
 
It needs a new a new impeller !----Find it right here on this site.------" engine diagrams "-----And just a few clicks.
 
Does the motor have the copper / bronze decals ?----Canada is fairly big I heard.----Takes me 24 Hrs driving to get out of Ontario if heading west.----If impeller has not been replaced recently you need a new one.-----REASON-----There is no warning system or shutdown feature on these motors.-----It will run until you notice a loss of power.----Then it is big $$$ and beer token repair time.----There is no difference between an American and Canadian marketed motor !!-----
 
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I did a quick search and all the Canadian serial numbers in and around your year and hp seem to start at 7 million where as the number you provided is 7 hundred thousand. Did you maybe miss a digit?
 
Here is a service bulletin for those motors regarding spark plugs. It won't let me upload it. Service bulletin 91-36 is the one you need
 
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racerone said:
So it has the copper / bronze colored decals ?-----Start with a compression test.----Post the numbers here.-----And it will need a new water pump impeller.-----Most of those I look at have an impeller that is old and cracked.
Click to expand...


Did a compression test just now. 130 and 135... is that good? I think it is...
 
I also changed lower unit oil, spark plugs and fuel filter... sprayed some of that carb gunk out and motor is running quite a lot better...
 
I am also enquiring about a Canadian Marketed 75 HP Mercury Mariner.

Do spark plugs really make that much difference?

It says for boats MFG in Canada & Belgium to use the NGK BUZHW-2. This is a spark plug with an inductive resistor. I called NGK tech and was told that due to a shortage in tungsten I beleive they were discontinued a year ago. Champion QL78V is supposed to be a replacement maybe.

Not sure how readily available these are.

Anyone know what the differences are between Belgium, & Canadian marketed motors over all the others specifying the NGK BUHW-2?

Yes my SN is A715190

https://www.marineengine.com/parts/mercury_marine_parts/sn/0A715190/ 7075726/277_40

https://www.marineengine.com/newparts/part_search.php?part_num=33-14103570&part_num=33-14103570
 
What is the actual difference between Canadian engines and all others?

I am in the same boat.

Supposed to use the NGK BUZHW-2 with an inductive reducer.

Spark plug is supposed to be discontinued.

What is Service bulletin 91-36? I see another person mentioned it.

 
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