2.5L Merc 280 Spark Plug Recommendation

[Brooks D'Antonio]

Hey guys,

I need some spark plug recommendations for my 2.5L merc 280.

Few weeks ago I had my motor serviced and completed gone through by a local shop that we have been going to for years (Bruce Dean Marine) and received his blessing on my motor for some good piece of mind.

Turns out his they had accidentally put the incorrect spark plugs back in the boat while replacing them.

First time out the boat ran great like it always has but this past weekend I experienced a few issues. After running the boat it sounded very loaded up under a load and would not plain out. Pulled the plugs and noticed they were not the correct ones. Had replaced them with an older set of BUH8’s I had in the garage from my last motor service and the boat ran... but still sounded loaded up and wouldn’t go about 4K on the tac..

My guess is the plugs I put in were fouled out too... but and suggestions? I have been told the correct plugs for that motor are the BUHW plugs by NGK...

Also, going to send my injectors out to be cleaned and flow tested (possibly could be the issue as well??)

Running have av-gas/ 91 octane mix with mercury performance plus oil at 32:1 as recommended when I purchased the boat.

Any ideas, suggestions?

Thanks guys,

-Brooks


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[Ragged Edge]

Here is Diamond Marine's suggestions.

http://www.diamondmarine.com/index..../engine-parts/engine-parts-page.htm~mainFrame

 

[Brooks D'Antonio]

Thanks for the link!


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[stoker2001]

BPZ8H-N-10 For 280hp
Projected tip = less fouling
Choice of top Offshore Racers

 

[Brooks D'Antonio]

BPZ8H-N-10 For 280hp
Projected tip = less fouling
Choice of top Offshore Racers

Thanks for the info!


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[Flying_Lavey]

I dot know the model of NGK I put in mime but neither my uncle or myself have ever fouled a surface hap plug in either of our carbed 2.4's. I think my last set I just changed out last year were on the boat when,I bought it..... 12 years ago. Just changed them out cause they were that old. Didn't notice any change to the engine performance.

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[NeedlesRat]

Hey guys,

I need some spark plug recommendations for my 2.5L merc 280.

Few weeks ago I had my motor serviced and completed gone through by a local shop that we have been going to for years (Bruce Dean Marine) and received his blessing on my motor for some good piece of mind.

Turns out his they had accidentally put the incorrect spark plugs back in the boat while replacing them.

First time out the boat ran great like it always has but this past weekend I experienced a few issues. After running the boat it sounded very loaded up under a load and would not plain out. Pulled the plugs and noticed they were not the correct ones. Had replaced them with an older set of BUH8’s I had in the garage from my last motor service and the boat ran... but still sounded loaded up and wouldn’t go about 4K on the tac..

My guess is the plugs I put in were fouled out too... but and suggestions? I have been told the correct plugs for that motor are the BUHW plugs by NGK...

Also, going to send my injectors out to be cleaned and flow tested (possibly could be the issue as well??)

Running have av-gas/ 91 octane mix with mercury performance plus oil at 32:1 as recommended when I purchased the boat.

Any ideas, suggestions?

Thanks guys,

-Brooks


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I would look at the manual for your year of motor as to what ratio to run. My motor is a 99 280 and is supposed to be ran at 40:1 per the manual. I’ve noticed my motor is sensitive to being to rich and will load up if it’s any richer than 40:1.


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[Brooks D'Antonio]

Hey guys, wanted to thank you all for input. Pulled my injectors last week to get flow tested and cleaned. Turns out I had two “leaky” injectors from what the shop had told me. Tested the boat this past weekend with freshly cleaned injectors, New plugs, good oil, and some race fuel (better fuel for some peace of mind) and it ran flawlessly. Better than ever actually. Glad it was only a minor issue. Cheers [emoji481][emoji481]


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[HST4ME]

The duty cycle for injectors in these motors is brutal, yearly cleaning and filter replacements are pretty critical.

 

[Brooks D'Antonio]

The duty cycle for injectors in these motors is brutal, yearly cleaning and filter replacements are pretty critical.

I’m going to do them at least once a season from here on out. Good peace of mind. Learning about these 280’s more and more as I go.


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