Spark Plugs

[troy994719]

I have a 2001 40TLRZ that seems to foul plugs frequently, the area that I run the boat in has quite a few long no wake zones and I have to run the engine at low RPM’s quite a bit. The carbs are clean and the motor runs great but after about 10 hours the plugs will have build up and the engine wont idle without stalling. If I put new plugs in it will idle fine.
Would it hurt to try one heat range hotter plug? B7HS-10 are the current plugs and it looks like NGK B6HS-10 would be the next hotter heat range. Thanks for the help.

[robert graham]

Better use the NGK recommended plugs, maybe try the Pennzoil 100% Sythetic Outboard Oil for cleaner burning. I got a spark plug sandblaster from Harbor Freight Tools for $18 and it works like a charm to knock carbon/deposits off plugs. It'll pay for itself many times over, because it's good for lawn mowers, cars, outboards, etc., probably not buy any more new plugs for a long time. You'll need a small air compressor to operate the sandblaster. Good Luck!

[StevoH2O]

You seem to be having the same issue as I have with my 92 Pro-V 200 plugs fouling. we should keep an eye on each other's posts to find ideas/suggestions.

[Tucker]

Guys, I have a 150 OX66 and have disconnected the oil injection and premix. I idle for hours and never have fouled plugs. Don't know about troy but Stevo you have oil injection and it sounds like the linkage is out of adjustment. What kind of solutions have you found by searching? I hear about this a lot, hence one of the reasons I disconnected the oil injection.

[troy994719]

What Kind of oil are you using?

Oil injection is disabled on mine and I run 50:1 premix. I am going to try switching oil to start with, maybe to Yamalube with fresh plugs for a few tanks. I have been using Pennzoil synthetic blend but it’s probably not the best oil.

[Tucker]

Troy I run Amsoil HP premixed 50:1. A little expensive, about $24 with my dealer discount. I also run Ring Free. Not too familiar with your motor but you may want take a look and the low speed adjustment on the carbs (if they have them). Might be a little too rich. Remember this is an air screw; so CW will make it richer and CCW will make it leaner. With your oil injection you may want to consider the Ring Free. It mixes at 1oz:10gal and I found it for about $28 quart.

[robert graham]

If your thermostat/cooling system is not allowing motor to reach a normal operating temperature range then it could cause fouling of the plugs. After normal running, remove motor cowling and put your hand on the cylinder head. Have you ever checked or replaced your thermostat? Good Luck!

[troy994719]

Yes I have checked the thermostat, its opening at the correct temp. I have checked the engine after running and it feels pretty warm, I think on a temp gun it was about 160. Might be worth replacing the thermostat just to be safe?
When I rebuilt the carbs I set the low speed adjustment to 1.5 turns as the yamaha manual stated. I really dont know much about fine tuning that adjustment. Thanks for the ideas and input!

[robert graham]

I run a pre-mix 90HP with the Pennzoil 100% Synthetic at 50:1 and have never fouled a plug. Maybe give that oil a try.

[citabriatom]

Troy,one other thing you could try is a fine wire plug(platinum or similar).These are more resistant to fouling than the standard plug and don't cost a whole lot more.NGK makes them as well as others.

[StevoH2O]

Stevo here with the Pro V 200. I have had the mechanic run 50:1 through the engine but it takes about 10+ hours of use for the plugs to foul. They are all equally saturated. Mechanic has dialed back the oil injection once - but is hesitant to keep doing so - for ramifications are expensive if modifications are too abrupt. Is the solution the oil pumping system? Mechanic says when it fails, it will pump like mad and save the engine.

I run no ethanol 92 octane gas, Yama Lube, and place ring-free into my gas. I pay - but it does not seem to play...

What is the ideal temp range when at normal operating range? I will get one of those temp guns for testing.

Does anyone think the issue could be related to a weak electrical impulse and hence the plugs fouling. When i am WOT with clean plugs this baby flies!

[citabriatom]

Steve,I hate to second guess your mechanic,especially since I'm not there looking at your engine.But since I have a 1992 ProV 200(modified),and a highly modified 220 Excell(which I just broke the other day),I'm going to throw my two cents in.If you want to call me an idiot later,get in line behind my wife(LOL).Anyway,I doubt seriously that you ignition is bad.This system is really reliable and believe it or not,is used as a popular modification on Evinrudes used for racing.The spark does not break down at high RPM's like the OMC does(I'm talking about HIGH RPM's).Have you tried pulling a plug and grounding it against the engine and cranking it over?Doing this in the dark will make it easy to see as the spark should be huge.If the spark is weak,check all of the grounds,especially the battery to engine ground(actually at the starter) and the coil to engine grounds(there are two,one at the base of each cylinder head;each set of three coils goes to one ground).An easy test would be to take a peice of wire and go straight from the battery negative and clip it directly to the coil ground and see if it improves.Did you disconnect the oil injection completely?I don't use it because I turn higher RPM's than the injection is designed for.It is a reliable system,but poop happens,and since all of the plugs are fouling,sounds like it may be the key.The way the 200 is set up for fuel pumps,a bad diaphram will only foul the one cylinder that it is picking up it's pulses from.It will run horrible,but the worst case is two plugs fouling if both pumps are bad.
(I run an electric fuel pump because of fuel flow and the use of a primer system instead of choke plates.)Hope some of this helps.

[Tucker]

Stevo, stupid question but I have to ask, when the mechanic switch over to premix he disconnected the the oil injection line right? Your problem is a real beaut. We'll keep this one at the top, somebody else has had to have it before and hopefully chimes in.