89 Merc Laser 200 - advice to stop plugs fouling?

[gmacrae]

Hi guys. This is my first post here but im going to be sticking around, have a fair bit to learn about the boat I've bought recently

Anyway, its a mid 80's ski boat with a recently rebuilt Mercury Laser 200 (injected). Its been built up to ski race, and as well as the rebuild, the motor's apparently had a few things done to increase performance (what that could be in a 2-stroke, i have no idea). I got a chance to talk to the guy that built the motor (a mercury agent here in NZ). He said that although it injects its own oil, to run a 70-80:1 mix in with the fuel. Its had its rev limit raised and this extra oil mix it just to protect it at high revs as apparently the stock oil injection wont quite keep up. This is fine, and the engine runs awesome, as long as you're able to keep plenty of power on, but it fouls the plugs fairly easy if you putt around as it sometimes needs to now, picking up wakeboarders, carefully warming up, staying under 5 knots around lake shore etc.

Am i able to decrease the rev limit (i assume electronic) back to stock and just rely on the stock oil injection again?

Would i be better to run a leaner oil mix? say 100:1?

Does anyone have any other suggestions that might help me out?

Thanks in advance for any pointers you can give me.

Gene

 

[Faztbullet]

Re: 89 Merc Laser 200 - advice to stop plugs fouling?

First is it smoking at idle? What is the max rpm you are turning? Does ECU on back side have a CDI sticker or in sharpie R&R and date wrote on it? Also is there a small hole drilled and filled with silicone on front of unit?

 

[raa711]

Re: 89 Merc Laser 200 - advice to stop plugs fouling?

That sounds like a lot of oil to me. Are you running past the recommended rpm range for the motor, and thus the need for additional oil in the fuel? Is the additional oil in the fuel recommended for the break-in period of the motor. I would think that a new or rebuilt powerhead, would experience some fouling of plugs until it is broken in.

 

[raa711]

Re: 89 Merc Laser 200 - advice to stop plugs fouling?

Sorry, just read your post a little closer. The 89 Merc Laser 200 is not what you might consider a high-performance and thus was designed to be run within a specified rpm range. If you are twisting it more than that, you might want to consider converting it to mixing oil with fuel only. There are block off plates that let you remove the oil injection pump and run premixed fuel. What mods were done to the motor: reeds, shaved heads, port work? For longer life, I'd stick to the normal operating rpm range for the motor. My guess is the added oil in the fuel is contributing to the fouling problem. Those surface gap NGK's get pretty expensive after a while.

 

[gmacrae]

Re: 89 Merc Laser 200 - advice to stop plugs fouling?

First is it smoking at idle? What is the max rpm you are turning? Does ECU on back side have a CDI sticker or in sharpie R&R and date wrote on it? Also is there a small hole drilled and filled with silicone on front of unit?

At idle it runs pretty clean. It does appear to be a nice tight engine if you were wondering about the rings. The tacho on the boat is hardly accurate, bounces all over the place and doesnt appear to read right when cruising/under load, though i've seen 8k a couple of times when free revving (in the water) trying to clear out the oil. Sorry man but i havent even seen the ecu (bigtime boating novice here), will pop the cowling off again in the next day or so and check it out. Is this how the rev limit might be raised? some kinda pot or resistor thing in there? Ill definitely check that out...

 

[gmacrae]

Re: 89 Merc Laser 200 - advice to stop plugs fouling?

Sorry, just read your post a little closer. The 89 Merc Laser 200 is not what you might consider a high-performance and thus was designed to be run within a specified rpm range. If you are twisting it more than that, you might want to consider converting it to mixing oil with fuel only. There are block off plates that let you remove the oil injection pump and run premixed fuel. What mods were done to the motor: reeds, shaved heads, port work? For longer life, I'd stick to the normal operating rpm range for the motor. My guess is the added oil in the fuel is contributing to the fouling problem. Those surface gap NGK's get pretty expensive after a while.

i would probably prefer to have the thing set back to a more stock rev range and use the oil injection system (they're reliable right?). Im getting in touch with the engine builder now to ask what he did to it etc... yea those plugs are fairly pricy alright, with the surpressor in them. Thankfully the new ones are lasting with plenty of 'spirited' driving

 

[raa711]

Re: 89 Merc Laser 200 - advice to stop plugs fouling?

8,000 rpm is way to much for that motor. A lot of your performance gains in the normal operating range will depend on engine height and prop selection. I would not run that motor more than about 5500-5800 on the top end. Oil injection is as reliable as how the motor is run and maintained. The pump runs off the crankshaft. The biggest problem when they fail lies with the plastic gear on the pump drive coming apart. How big is your boat? Is the motor mounted to the transom or is it on a lift plate. What kind of prop are you using. Lots of factors here to consider when attaining maximum performance.

 

[Faztbullet]

Re: 89 Merc Laser 200 - advice to stop plugs fouling?

These engines (EFI) have a different style bleed system than a standard V-6.The bleed lines have a filter on it so it doesnt contaminate the VST tank on return.I would check filter(#10) to see if clogged as this will cause plugs to foul at low speeds.

 

[gmacrae]

Re: 89 Merc Laser 200 - advice to stop plugs fouling?

raa711: thanks for the reply. I cant be certain that was an accurate reading from the tacho, its one thing i really have to sort. Im not after more performance, the boat goes like a rocket already, and gets a bit scary over about 60mph. It was owned by a boat builder and set up by a big mercury agent to go fast for his ski racing so im not planning to improve on things there, just want it a bit more tame for the use i give it really. They use plastic in the oil injection pump??? Surely thats a bad idea? Starting to wonder if it might be less of a headache without the injection setup.

Faztbullet: Cheers ... bleed system? sorry man, ya lost me already. I gather you're talking about the oil delivery... I'm taking it in to a local crowd to give it a good once over tomorrow. Will mention what you've said about that bleed line filter to them.

I talked to the guy that built the motor today. He said he only advised the previous owner to run 80:1 as well as the injection because he was going to be WOT for long periods racing. He said the way im using the thing, there's no need for the double mix and the injection setup will keep up fine. So i'd say there's my solution right there... though i'd really prefer to have the injection system removed and run my own mix - less to worry about the way i see it.

 

[tashasdaddy]

Re: 89 Merc Laser 200 - advice to stop plugs fouling?

the motor is designed to run 50:1, OMC, tried 100:1 and recinded that years ago, do to bearing failures. so if you want to keep it running, use 50:1.

 

[gmacrae]

Re: 89 Merc Laser 200 - advice to stop plugs fouling?

the motor is designed to run 50:1, OMC, tried 100:1 and recinded that years ago, do to bearing failures. so if you want to keep it running, use 50:1.

did you read that it also runs oil injection? Anyway thanks, if i remove the injection setup ill mix in 50:1