definitely the NGK v power plugs, very reliable and not prone to fouling easily

Many of us run 20/50 oil in our marine 502's and personally I prefer the Mobil 1 v-twin 20/50 or equivalent. Unlike a street motor, marine motors operate at a much higher torque load at all times and the oil has more work to do,

there are many opinions out here on the subject however.


I run my v-twin 50 hours with the m-1 filters. We also ran it in our modified lite dirt race cars.

Royal purple race 51, a little expensive but well worth it.

In that setting I would use Amsoil Marine 15W-40 synthetic oil in a big block 502.

http://www.amsoil.com/storefront/ame.aspx

Let the engines warm up real good before hitting the sticks.

The original owner was using penzoil racing oil but I had several people tell me thats not a great idea

Some racing oils do not have detergency additives and thus are meant for one race or "heat" and then drained. Carbon particles accumulate and cause accelerated wear in oils with no detergency; detergents and dispersants bind them up and keep them dispersed.

The 15W-40 Amsoil is as low that I personally would go in a multi-vis lube for a 502.

Quite frankly I would be surprised if Mobil-1 15W-50 would not do the job for you as it pumps well at lower temps.

For the last couple of years I've been running Kendall GT-1 straight 40w in my 502 mpi I had heard that the Kendall GT-1held better oil pressure than most oils because it would not airerate like other ? From what I've seen I will keep using it.

My new boat has HP500 efi's, what NGK plug would I use in these engines ?

RED LINE ALL THE WAY NOTHING ELSE!!!!!!!!!!!!!!!!!!!!!! There 10 40 has the same viscosity as a 20 50. I used this in my blown 502 for 3 years almost 450hrs. Just tore it down to build a 522 the inside looked almost new! Champian race plugs!

A 10w40 can no way have the same viscosity as a 20w50, if it did they would call it a 20w50.
Ken

Redline states that their 10W-40 Syn has the same bearing and boundary lubrication properties as a conventional 20W-50.
Viscosity is still a 10W-40.

Thats what i was getting at relax GUY!