1999 5.0L spark plug info needed

[bolo78910]

hello guys for my 99 mercruiser 5.0L thunderbolt iv , i know it call for spark plug mr43Lts , what other plugs can be used on this engine.??? engine serial # , # 0L612762 i am getting a hesitation at lower rpms but over 3500 it smooth out. at about 2000 rpm it heasitat go hesitate go. just wants to throw in some new plugs and see what happens thanks

 

[Don S]

Re: 1999 5.0L spark plug info needed

Sounds more like you have a carb problem, not spark plugs. The NGK BPR6EFS is what you get if you order from Mercruiser.

 

[bolo78910]

Re: 1999 5.0L spark plug info needed

someone told me the same thing too don, and thanks for the info. is it normal for at the first start up after sitting over night , i look at the exhaust coming out in the dock and the water looks oily/gassy anitil it warms up it goes away. that seems like carb.

 

[Don S]

Re: 1999 5.0L spark plug info needed

i look at the exhaust coming out in the dock and the water looks oily/gassy anitil it warms up it goes away. that seems like carb.

Sounds like the choke is working to me, but after it warms up, it should run fine at 3500 and 2000 rpm without hesitation and surging. It could however, be the sparkplugs or just in a bad need of a full tuneup? When was the last full tuneup and compression check. You can't tune a carb if you don't have good compression and spark at the right time.

 

[bolo78910]

Re: 1999 5.0L spark plug info needed

did not change the plugs this season don but i did last season. and as from my past thread, i did found a bad spark from what looks like a manifold/riser gasket leak .
i will pull all plugs and change, cap roto distributor sensor are new this season.
thanks

 

[bolo78910]

Re: 1999 5.0L spark plug info needed

update i change out the old spark plugs and put in new champion so far all the plugs looks great but #1 look black #5 which was the one that i think water might gets to it from a bad riser/manifold gasket that one looks a little clean , then again i did swap that single one two weeks ago. i have pice with all the old plugs but i cant find a way to upload them. as i said the test run was great no more sighn of bogg boggy down. i retork the riser manifolds bolts next time after a run i will pull plug number 5 as soon as i shut the engine off and see if water comes out. risers/manifold was new last season. thanks don s you seem to always nail it .

 

[Don S]

Re: 1999 5.0L spark plug info needed

update i change out the old spark plugs and put in new champion

Put in some NGK, or the proper AC, then see how it runs. Champions are the worst choice you could have made for sparkplugs on a marine engine.

risers/manifold was new last season

Did you check the gasket surfaces for flatness? Bond-o bought a set of GLM's that leaked until he flatted the surfaces. The were bad from the factory.