[Juskol18]

I have a 1998 mariah shabah 202 w/5.7 carb mercruiser alpha one outdrive.. I took the boat out yesterday and it was spitting and sputtering, upon looking into the motor i found that the spark plugs were in extremely bad shape. i need to replace them but i want to make sure these are the proper plugs. The plugs i just removed are ACDelco 41-993, but as i read online most ppl i see are using mr43t plugs? i have been researching for hours and am having no luck! could someone tell me which is the best plug?

[husker_fan]

The 993 is an iridium plug vs the 43t, which is just a standard plug. The R43TS was the standard plug used in almost every small block Chevy for years so its really common. The iridium plug is definitely better, but probably a fair amount more expensive, but will last at least twice as long.

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[Juskol18]

thanks so either one should be fine??

[husker_fan]

Yep. Either will work fine.

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[Motoxxx43]

Spitting and sputtering... Had that problem many times before in my personal boats and in friends boats. If you are going to do the plugs you may as well spend the extra $ on a new water separating fuel filter. I recall the WIX 33225 going for 14$ at the autoparts store and I run that filter in the 4.3 and the 7.4. I dont know if it is the ethanol that is the culprit for the contaminated filter but it has become an annual change for us and here in Colo. even though we are in a very dry climate. Last season I started running an "ethanol" treatment in my fuel. Plugs looked great out of the 4.3. Have not had the 7.4 long enough to notice. More on that later...
Here is a link for you of all the cross referenced filters if you are interested--->
FRAM - Part Details

[Juskol18]

yes i plan on changing the water separator also.. i wish i could post a pic of the spark plugs, i have never seen any this bad

[Motoxxx43]

What do you have going on with them? Rust? Black N wet? Roasted gold? Crispy white? Corrosion? Could be a carb adjustment as in electronic choke malfunction, plugged jet, etc. Maybe it came from sea level and you are at elevation making it run rich? Lots of things to consider. Can be a simple fix.

Are they original plugs?

[Juskol18]

idk if they are original plugs but one of the the part where the center core sparks to is completely gone (like the thing you gap)the color looks good other than that, the boat has 346 hrs and has been rebuilt maybe 100 hrs ago so i would have thought they replaced sparks plugs... what could cause this?

[husker_fan]

That's not normal for any amount of time they've been in. I'd check that cylinder for problems. At the least run a compression test, and best case a leakdown test. Sounds like there might be something funny going on in there. Only a super lean condition could burn that off, or mechanical failure could break it off.

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[husker_fan]

Here's a chart..

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