Spark plug size

[1979 Quartermasters]

Hi guys. Have aquired a new to me boat. Its a 1995 Sea Ray With a 5.7 (0F372090) And a Alpha I Gen II. I ordered spark plugs and the ones they gave me are the same number(ACDelco MR43T) as the ones that were in the boat, but longer. Managed to put 5 of them in before I noticed they were longer. The boots fit on but are against the manifold. Is this a big deal.
Also there is a milk shake in the trim resevoir. I want to bleed that crap out and refill and see if it does it again. Is this a bad idea? I'm wondering what kind of fluid we put in the trim system.

Thanks Ken

 

[Pete104]

Re: Spark plug size

Don't worry about what you see of the spark plug. In your case the thread length is what counts!

As far the trim oil, plan on putting rebuild kits in the cylinders. Unless you have water coming in from above, dripping on the trim motor!

 

[Don S]

Re: Spark plug size

The MR43T is the correct plug, what was the number of the plug that came out?

PS: Your SN if for the outdrive, not the engine. so it didn't help at all.

10W30 or 40 for the trim oil.

 

[1979 Quartermasters]

Re: Spark plug size

Thanks for the quick response.

The correct serial number is OF363726
The number was the same on the old ones, they were shorter so the boots wouldn't hit the manifold.

The trim still works good. Is there a way to tell where the water is coming from. How difficult is this cylinder rebuilding process

 

[Pete104]

Re: Spark plug size

It's not so bad. The worst part is getting the end caps off, if you have a corrosion issue it can be VERY difficult. Requires a special tool.
Don't wreck anything!
Water finds it's way in from anywhere. I would make sure that rain water isn't traveling thru the cover to molded fiberglass leading to drip smack on top of the fill cap on the resovoir! After that, look for oil rainbows in water.

 

[WashmanToo]

Re: Spark plug size

My 97' Bayliner Capri with a 5.7 Mercruiser says to use AC Delco MR43T plugs on the flame arrestor cover.

When I changed the spark plugs the first time after buying the boat, I found out they had
been switched out with NGK plugs.

The MR43T crosses to NGK BR6FS which has a tapered Seat and a reach of 10.9 mm (.460?)
Someone had installed NGK BR6EF which has a tapered seat and a reach of 17.5 mm (.708?)

Which means they were sticking into the cylinder almost a 1/4" too far. Gaps were everywhere from .024 to .029 inches so it appears that they were just barely touching the tops of the pistons.

I replaced them with AC Delco Rapidfire 10 (Platinum, Tapered Seat, 14mm Thread, .460 in. Reach)

Make sure they gave you the right reach plugs!

 

[Don S]

Re: Spark plug size

The number was the same on the old ones, they were shorter so the boots wouldn't hit the manifold.

Sounds like AC may have redesigned the spark plug and made the insulator longer. If that is the case, go to the NGK BR6SF for your serial number engne.

 

[Dryon]

Re: Spark plug size

Solid or screwed terminal on spark plugs?