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Mercury XR2 Black Max fowls plugs

T

tbrownarcher

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XR2 Black Max fowls plugs

Our boat is a 1999 18 ft Triton 180 Premier.
Our motor is an XR2 Black Max 150 HP.
The Serial # is B176785

Our motor fowls the plugs and then it's of course hard to start and does not run really well for quite a long time of full throttle. The motor does clean the plugs or heat up enough to run well after a long time at full throttle. We can also take the plugs out and clean them with spray on carburetor cleaner which makes it run like crazy.

What is happening is that we have to idle the motor a lot because the lakes around here are no wake or 5 mph for the most part and so we are not able to send it flying like it needs to be.

We disconnected the oil pump and run without the pump mixing the gas/oil ration ourselves. We do this with a critical eye at a 50:1 ratio which is what we understand it should be run at. The motor being a 1985 we don't want to be running it when the oil pump goes out and can't afford a new one. We don't trust a new one either so we prefer to mix the oil and gas. Oh yeah! we fill it with regular gas (no alcohol).

The obvious question is what can we do to fix this? Since we would do the work ourselves we also need any tips to do the work that anyone thinks may be helpful. We will buy the OEM book.

Thanks,
Nate​
 
The plugs are BU8H? Very hard to foul up the surface gap plug. :confused: Must be some really bad gas and oil laying down carbon. The motor would not run if the carbs were spilling that much gas. The only other place gas can leak is the fuel pump diaphram. Probably should be checked/ replaced on a motor that old.
 
Hello Nate, I will assume you are getting an "oil foul" (black goopy mess) on the plugs from your description so will talk to that point.

Running pre-mix certainly doesn't help the issue to start with. The oil pump on these models uses/used a variable metering system so they would mix at 100:1 for idle and upto 50:1 as you progress to full throttle. So by pre-mixing you are already feeding the motor twice as much oil at idle for the design.

That can be overcome somewhat by otherwise keeping the motor well tuned. To that end I would ensure:

you are running the correct sparkplugs - NGK BU8H surface gaps (these likewise, don't help your cause - surface gaps do poorly at idle speeds but I don't see a cross ref to a gapped plug) - and don't substitute to a Champion plug - they won't work correctly especially at idle

check/replace your thermostat - if the engine is running a little cold that could hurt as well - 2 stroke oil will mostly "burn right up", so a slightly "cool" "over-oiled" engine is a double whammy

have the carbs adjusted a little leaner - most are set slightly "rich" as standard practice - since you have "extra oil" at lower rpms, a slightly lean mix should not pose a problem

(now for the sermon :))

I have never personally seen an underhood oil pump fail and cause engine damage (although I'm sure there are a few cases - just significantly less than you would suspect). The gear driven oil pumps that Merc uses are pretty solid kit and will often outlast the life of the motor. With engine oil running 15-35 bucks a gallon, depending on how much you use your motor, the oil savings from using a variable pump (and the extended sparkplug life) could easily pay the pump cost in a couple of seasons. While they may require occasional service, over the life of the motor your operating costs will be significantly less, and the motor will perform better, with the oil pump in place..
 
Mix the oil at 50:1 and sleep well at night.------------------Make sure the thermostats are in place and that the poppit valve is in place.----------A cold running motor is not good.---------------Make sure that spark will jump a gap of 7/16" on all 6 cylinders.---------------I would not trust the " plastic gear " that drives the oil pump on those motors.-------------Motors in the old days would idle all day long on 24 : 1 and never foul a plug , if the motor is in good shape.
 
Yes!!!!!!!!!!! It's actually oil that fills the hole maybe a bit of carbon but it's mostly liquid. So, it's not carboning the plugs it's just filling the hole with oil. Sorry about the description ...

Nate
 
Nate,have u got your motor problem fixed yet!
I've just joined this forum and read your problem on your xr2!!!
If u have gotten it fixed by now,no problem, if by chance u haven't got it fixed by now,I can tell u exactly what's the problem and how to fix it, and the parts are less than 5 to 7 dollars.

To try and explain how to fix it would be very hard in an e-mail,but if u wish,u can call me @ 1-574-674-8363 and I'll explain to u how to care this problem for ever.
I bought my 1985 cajun 185 fishing machine new with 1985 xr2 with it, had the same problem with mine.
I do all my own work on my boat and cars and computers.
So Nate,if u wish,give me a call, I think u be supprised how easy it will be to fix that problem,and*I will give u alot of tec.info on what really caused the problem in the the 1st. place.
Thats it for now unless u call,ok!

******************************************** Norm.:cool:*
 
nujac18 said:
Nate,have u got your motor problem fixed yet!
I've just joined this forum and read your problem on your xr2!!!
If u have gotten it fixed by now,no problem, if by chance u haven't got it fixed by now,I can tell u exactly what's the problem and how to fix it, and the parts are less than 5 to 7 dollars.

To try and explain how to fix it would be very hard in an e-mail,but if u wish,u can call me @ 1-574-674-8363 and I'll explain to u how to care this problem for ever.
I bought my 1985 cajun 185 fishing machine new with 1985 xr2 with it, had the same problem with mine.
I do all my own work on my boat and cars and computers.
So Nate,if u wish,give me a call, I think u be supprised how easy it will be to fix that problem,and*I will give u alot of tec.info on what really caused the problem in the the 1st. place.
Thats it for now unless u call,ok!

******************************************** Norm.:cool:*
Click to expand...
I have the exact same motor and you seem very knowledgeable. Mine is hard to start cold, it can take something like 30 tries turning the key before it starts, but once warmed up it starts on the first try. What could be the problem?
 
Good Morning All,

I am a newby to this forum deal but I am hoping someone can help me with some issues I am having with my XR2 150. I too am having fouling problems and there are several things I have noticed with the motor that I would like to know if they are normal. First off, the fouling plugs.........I am using the NGK BU8H surface gaps plugs and have replaced them twice. The reason I replaced them the first time was that the motor had sat for 10years without being run. The second time was due to the fact that the motor was hesitating to "hook-up" when I punched it. Over time the problem got worse until the motor would loose power and then begin getting hot. To that end I suspected that the plugs were fouled again and perhaps something was wrong with the carb adjustment. Being unfamiliar with making adjustments on the carbs I went to the next best thing and rebuilt the fuel pump. I also checked the compression on all the cylinders to make sure I didn't have a dead can. All read over 105 psi but there was a spread of about 15 psi between the high and low. Cylinders 2, 4 & 6 ran on the 115 to 120psi range and 1,3&5 ran from 105 to 112 psi. Back to the fouled plugs, cylinder 2, 4 & 6 had much worse fouling than the others. Don't know why that was.....Anyone? At any rate, when I tank tested the motor and even when it was running well on the lake it always seemed to smoke really bad and smell a bit like it was constantly running rich. Is there a way I can check to see if the motor is getting too much oil?

The final issue relates to the flow of water out of the little hole just below the power head. It is my understanding that if the pump is functioning correctly there should be a steady stream of water, 2-3 feet out from the motor at idle and then a strong stream at the higher rpms. In actuality the stream is intermittent at idle and so-so at full throttle. I change the pump and housing 10 motor hours ago and it didn't seem to make a big difference. I also had the thermostats and temperature sensor changed last summer. I am wondering if this is normal for this motor. Any help with what I have been dealing with would be greatly appreciated.
 
nujac18 said:
Nate,have u got your motor problem fixed yet!
I've just joined this forum and read your problem on your xr2!!!
If u have gotten it fixed by now,no problem, if by chance u haven't got it fixed by now,I can tell u exactly what's the problem and how to fix it, and the parts are less than 5 to 7 dollars.

To try and explain how to fix it would be very hard in an e-mail,but if u wish,u can call me @ 1-574-674-8363 and I'll explain to u how to care this problem for ever.
I bought my 1985 cajun 185 fishing machine new with 1985 xr2 with it, had the same problem with mine.
I do all my own work on my boat and cars and computers.
So Nate,if u wish,give me a call, I think u be supprised how easy it will be to fix that problem,and*I will give u alot of tec.info on what really caused the problem in the the 1st. place.
Thats it for now unless u call,ok!

******************************************** Norm.:cool:*
Click to expand...
Hi Norm, I have a 87, can you advise me? thanks.booger
 
Hi Norm, I have a 87 xr2 fouling plugs and smoking alot till gets warm up. Could you share some of that knowledge with me. Thanks, booger ball
 
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