1995 Merc Question?

[Kingfisher]

Our 1995 90 HP Merc tiller starts to miss half way through the summer each year. We install new spark plugs every spring, and have to put in a new set half way through the season, then it runs great again. Is this normal?

[marine_man]

I wouldn't call it typical.

Do you do a lot (and I mean a lot) of trolling with this motor?

It's possible the cylinder gets loaded up with fuel and fowls the plugs.

What do the plugs look like when you change them? Do they all look the same?

marine_man

[Kingfisher]

mm, thanks, we have a 15 hp Merc for trolling, so the 90 is used primarily to reach our fishing spots. We do most of our fishing on LOW so 3 to 10 mile run's are the norm. All 3 plugs look the same-wet.

[Whoaru99]

Personally, I've never much liked the way my 96 Merc 90hp runs from about 2500 RPM and below, it's rough, spits and sputters, shakes a lot, etc. The carbs have been gone through and no real difference in how it runs there.

Runs great from 2500 to WFO.

Can't say I've had much problems with plugs fouling if I'm keeping the revs up. But, if I putz around a while it'll eventually load up, seems to clear out pretty fast once you pour the coals to it.

I've probably put only a few sets of plugs in mine. In fact, I think I still have the factory plugs in the cubby hole.

Mine has the surface gap plugs in it, yours too?