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200 BlackMax Questions

USAFaggie

USAFaggie

Member
Hey guys (and gals). I have a few questions for ya'll. I have an 87 Merc BlackMax 200 hp motor on my 87 Eluder. It sat in my garage for 6 mo. without being run and I probably didn't winterize it like I should. Of course it ran like crap when I first took it out last week beacuse the gas was bad. I had put in stabil when I stored it and then I put in some water remover and sea foam and filled the rest of the tank up with good gas and new Merc Synthetic 2-stroke oil. It had about 1/4 tank of bad gas so it shoul dbe pretty well dilluted. I ran it two days ago and it was doing better, but not great. It idles fine, and when you gun it it accelerates for a few seconds fine, then it stumbles on its face. It is like it is bogged down. If you give it mroe gas it does rev up it just runs rough and sputters etc. I got some carb cleaner yesterday and sprayed some into the intake and that seemed to do the trick. It was running like a bat outta hell. It had great acceleration and top end. However, after about an hour or so of running, it sputtered while at WOT and was doing the same crap again. I used the B-12 carb cleaner again and it started running good. What gives? Is it just the bad fuel and all the addatives? I had changed the plugs last week and I checked them yesterday and they were pretty wet, but they werent charred.

Ok second set of questions: I want to start getting into doing some light engine work myself. What are some easy mods can I do to wake this motor up a little bit? Are there any essential mods I should do even though I might have to take it to a shop? Thanks!!!!

Ryall
 
Black Max 200

First thing you should do is disco the fuel line and crank the engine over so the fuel pumps into a glass container. After approx two to three inches of fuel, check for water-it might be a good idea to install a water seperator since they are mixing alcohol (10%) into the gas... Alcohol loves to attract water and it is going to be a big problem with all Gas Fired DINO FUELED Engines... If water is not the problem check Fuel screen and tear down the carbs it's easy to rebuild the CARBS just get the Mercury Repair Book. Good Luck!
 
im guessing you are talking about disconnecting the line at the carbs right? I was thinking about installing a water separator eventually, look slike a good investment. When you say fuel screen are you talking about the inline filter? I just replaced that..... I've never really done any engine work, esp. on an outboard! I do have the Merc manual though!
 
water in gas

You can also disco at the primer bulb " I had a brain cramp " thinking of a fuel pump type car engine. Pump bulb instead of cranking engine sorry-the fuel screen is where the fuel line attaches to engine, also check the fuel pump that thing has a diaphram in it check Merc Book. Hope this helps.
 
Yeah that should get me on the right track. I just remembered that my Merc book is packed away in my household goods shipment since I just moved AF bases. I might not be moved into permanent housing and have my stuff delivered for another 2-4 weeks!!!!
 
Excuse my ignorance as I am still learning all this stuff, but when you rebuild a carb what exactly are you replacing? The jets? Cleaning out the bowls? Why would shooting the carb with the carb cleaner make it run great for a while and then why would it foul up again? Could it be the addatives? You would think that 3/4 tank of good fuel would dilute enough of the bad fuel.....
 
Carbs

You replace gaskets, set the floats clean the jets. When i replaced my powerhead two years ago the re-rebuilt my fresh rebuilt carbs and the replaced the main jets. I have an 84 lower unit with a 89 NOS powerhead.. I see you are in the service, in N.J. we have a lot of Bases i was just at Ft. Dix which is next to Lakehurst and McQuire AFB.
 
Untreated gas can turn to jelly. It clogs up the tiny passages in the carbs. Or it could be water in the gas. either way try running it on a remote tank of new clean gas. If it runs fine then the problem is in the tank still and you have to drain it and start again. If it still does it then it is gunk in the carbs. Try draining the carbs. It may work it's way out or you may have pull the carbs, disassemble, clean and blow out with air. Might as well rebuild them if it come to that. If it does start running fine, no point rebuilding the carbs.

There is really no simple do it yourself mods for that motor.
 
Sound like you have some junk in the tank and its getting into the carbs.
As far as mods go, no real simple ones. One of the best bang for the buck mods is shaving the heads to raise the compression ratio. A good winter project. Pull the heads and send them off to someone like simon motorsports.
 
cool thanks guys. i guess I will have to try and rig something up with a 5 gallon gas can. I really hope there isn't a load of gunk in the tank. That thing looks like it would be a pain in the arse to take out and have cleaned. what can you do to drain the carbs without having to remove them? like i said earlier i dont know much and my merc book is packed away! i gotta start somewhere! thanks again!
 
There is a drain screw on the bottom of each float bowl. If you back it, it should start to purge. Then pump the bulb and it will flush it out.
I had water in my tank once. It drove me crazy trying to solve the problem. Finally drained the entire tank and problem solved. It does not take much water to make it run badly. Everytime I drained the carbs it ran well for awhile until that little bit of water made it's way back into the fuel system and it ran like a tank.
Try the remote fuel tank...it's quick troubleshoot!
 
I have also seen the mechanics disconnect the fuel line from the engine & pump the primer ball so gas from the tank goes into clear container to check for water .
 
well I pumped some gas into a glass and didnt see any water or a lot of gunk in it. I almost drained all the gas when I was boating yesterday, and bought a tank to pump the rest of the nasty stuff out. shold I just let it air out after that? or do I need to physically take the whole tank out and have a shop professionally clean it? also, can you tell me exactly which screw is the drain screw? like I said my book is at the movers warehouse and I dont wanna just start unscrewing things!!!!!!!!!
 
USAFaggie said:
well I pumped some gas into a glass and didnt see any water or a lot of gunk in it. I almost drained all the gas when I was boating yesterday, and bought a tank to pump the rest of the nasty stuff out. shold I just let it air out after that? or do I need to physically take the whole tank out and have a shop professionally clean it? also, can you tell me exactly which screw is the drain screw? like I said my book is at the movers warehouse and I dont wanna just start unscrewing things!!!!!!!!!
Click to expand...
For peace of mind I'd want to see inside the tank. Only way to see I can think of would be to remove the fuel gauge sending unit & then with a flashlight & maybe a mirror have a look.The bad stuff, if any should be in the back & bottom of the tank. If you can get the remaining water & trash out you should be fine. After bad fuel, you should go thru the carbs. If in doubt find an outboard tech.
 
It would be a good idea to get one of those inline filters also. By the way how old is the fuel line, primer bulb anything fuel related check it out
 
Awesome, you guys are too good! Today I actually removed the tank and took it to a shop to have them clean it out. I am replacing the fill hose because it was starting to deteriorate. The line from the tank to the engine looks good still. There is no wear or cracking. Now that the tank is going to be powerwashed on the inside there is no excuse for nasty stuff! Now I just need to drain the carbs and install the big water separater/filter. The inline filter is brand new in the engine compartment. Hopefully that will cure it. If not I guess she is goin to the shop :( Oh, and I checked my plugs again, then they were still a little wet, but there isnt much black crap on them. Actually they are still pretty clean, so no fouled plugs yet. SHould they be wet at all?
 
Well, I took it out after having the tank cleaned and the water seperator installed. The top end seemed great, but the acceleration SUCKED. It would bog way down and you wuold have to slowly increase the throttle to let it catch up. Made towing a knee board a real pain in the ass. It did run fast once it got going. Twice while running it at WOT it sort of bogged down, and once I stopped and got on a pane again it was fine. Also the overtemp horn went off twice while towing the knee boarder. That has never happened before and the engine has a nice pee stream coming out.

I still haven't tried draining the carbs. I got my manual but to be honest there isn't a "drain screw." THere are some screws that probably are the drain screw but they are all jet screws etc, and I am scared that if I take those out I will screw it up. If you take them out do they have to go in a certain amount to tune the carbs like a needle valve? I have a can of Mercury power tune I wuold like to run through it also to see if maybe carbon buildup is the culprit. That will be a PITA since you gotta take the cowling off and squirt it in the carbs while it's running. Is there a vacuum line or something you can squirt it in?

I really don't want to have to ake it to the shop b/c they said it wuold be 2.5-3 weeks to get it back. But at this point it looks like a carb rebuild is what is needed and I do not have the balls or certainly the time to do so. We hit the flightline on Wednessday, so my time is about to go from nill to non-existant except for Saturdays.
 
Merc Problem

If you can not locate your merc book buy another! Working on a merc or anything else that you don't understand is useless... The Horn alarm might not be the temp alarm! Caution befor running the motor, the OIL PUMP DRIVE GEAR MIGHT BE FAILING!!! Thus no OIL and Then A Blown Engine...
 
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