1986 Merc 150 Black Max hard starting and overloading fuel

[Gary Lee]

Hello. I have an 86 150 that is getting harder and harder to start. I almost ran the battery down yesterday before it finally kicked. I have tried pumping the bulb a lot, a little and everything in between. I run non ethanol, and have been adding Startron. Once it starts that first time, it starts the rest of the day with just a flip of the key-very fast. But then, next time at the ramp, here we go again. It also loads up on fuel, if idling (idles poorly too) out of a no wake zone or anything more than a few minutes, it bogs down and just won't jump out of the hole. I can throttle it up in neutral for 30 seconds or so- I guess that burns up the excess fuel- and then she'll go. Once up and at speed it runs like a scalded dog. Any ideas where to start? Thanks a lot.

 

[aussieflash]

Re: 1986 Merc 150 Black Max hard starting and overloading fuel

I would start with a carb service.Needle may be sticking causing flooding.Replace all needle seats and gaskets,soak all metal parts in carb cleaner and blow out all crevices with air gun.Check floats are floating and reset to correct height(1.6mm) 1/16".
Check your starting procedure and that push key choke is working,check all choke lines are connected.

 

[Gary Lee]

Re: 1986 Merc 150 Black Max hard starting and overloading fuel

Thanks, aussieflash. Sounds like a good place to start, I was kind of thinking carbs might be it. I will get around to it hopefully soon. I appreciate the help.

 

[Gary Lee]

Re: 1986 Merc 150 Black Max hard starting and overloading fuel

Thanks, aussieflash. Sounds like a good place to start, I was kind of thinking carbs might be it. I will get around to it hopefully soon. I appreciate the help.

Well, I have removed the first carb, and it looks pretty clean inside-maybe from all the Startron I have run through it. I am ready to order some parts now, but have a few questions if I may. I will be ordering float needles and seats for sure. I am also wondering about the idle jets (since it seems to load up while idling for any length of time). In searching back through the archives, I found a thread about similar issues on a similar engine (XR4, I think. Mine's an XR2), and it was mentioned that perhaps the idle jets should be changed for a different size. Like mine, his engine had .048 idle jets, and it was suggested that maybe .052's should be used. Any ideas about that? Also, the floats in these carbs (WH 40's by the way) are a hard plastic type material, I'm thinking that maybe they have been replaced in the past. I'd get new ones if I needed to, but if I don't need to, I'd rather not spend the $90 for them. Is there any way to tell if they are still good or not? Also, in some other threads I saw replacing the "reeds" mentioned. If that sounds logical, is there another name for reeds?, I can't find them on the parts list. I will also order all new gaskets. Anything else I should consider ordering? And just a couple of more things while I am at it here if y'all would be so kind-- I want to disable/bypass the oil injection. Is there a special part/parts needed? And lastly, I will replace all the fuel lines/ tubing in and around these carbs. Can I just get these at my local auto parts store, or should I order some with the rest of the parts I will be ordering? Thanks a lot, folks. I appreciate everyone's willingness to help. This is a great forum.

 

[j_martin]

Re: 1986 Merc 150 Black Max hard starting and overloading fuel

Jetting varies widely with the carb model number. All the WH carbs look the same, so until you find the WH model number on the carbs and look up the stock jetting, you have no clue as to what you have.

Unless you're made of money (and time) start simple. Unless they get full of water and stand for a year or so, the needles and seats usually are fine. Gaskets and float level are critical. If you have the old foam floats in it instead of the hard plastic ones. likely they are sinking. The best way to get a set of plastic floats is to score a rack of carbs off a later engine on eBay. Anything 88 or later, 135HP or higher, WH-(xx) will work.

That little innocuous gasket in the middle of the float chamber is famous for causing these symptoms. So is slightly high float setting. Both can be fixed with just the 5 buck gasket kits.

<edit> one more thought. If your fuel lines are old, you could be shucking hose liner paticles into the carbs, fouling the needles. Should be evident when you pull out the seats (to check this, and to replace the paper gasket under it)

To avoid the banhammer, I'll skip any discussion on fuel quality.

 

[Gary Lee]

Re: 1986 Merc 150 Black Max hard starting and overloading fuel

Jetting varies widely with the carb model number. All the WH carbs look the same, so until you find the WH model number on the carbs and look up the stock jetting, you have no clue as to what you have.
or later, 135HP or higher, WH-(xx) will work.


<edit> one more thought. If your fuel lines are old, you could be shucking hose liner paticles into the carbs, fouling the needles.

Thanks, John. The carbs are WH 40, and the stock specs call for the .048 idle jets. I replaced all the fuel lines/bulb, etc., from tank to engine, but now, I think I need to replace all the little lines in and around the carbs. Thanks a lot for your help.

 

[j_martin]

Re: 1986 Merc 150 Black Max hard starting and overloading fuel

The fuel bleed lines on the engine will greatly affect idle. The little enricher lines that go from the top carb fuel bowl to the enricher valve and then to the carb bases is no big deal except for cold start.

Didn't notice you already had the hard plastic floats. Shake them. If they don't have any liquid in them, they're fine.

Wouldn't hurt to try larger idle jets. Don't hold your breath for a cure, though. These carbs are pretty simple, and have to idle rich or you won't have any throttle response when you can it.

A dozen bolts and a few bleed lines, and the reed bank right behind the carbs is off for inspection. It's pretty easy to tell at a glance if the reeds are bad. You need to replace the gasket under the reed bank if you do this. There is really no other way to properly inspect the reeds. If you want to replace them, I's suggest Chris Carson reeds and hand lapping the reed blocks.

 

[Gary Lee]

Re: 1986 Merc 150 Black Max hard starting and overloading fuel

The fuel bleed lines on the engine will greatly affect idle. The little enricher lines that go from the top carb fuel bowl to the enricher valve and then to the carb bases is no big deal except for cold start.

Didn't notice you already had the hard plastic floats. Shake them. If they don't have any liquid in them, they're fine.

Wouldn't hurt to try larger idle jets. Don't hold your breath for a cure, though. These carbs are pretty simple, and have to idle rich or you won't have any throttle response when you can it.

A dozen bolts and a few bleed lines, and the reed bank right behind the carbs is off for inspection. It's pretty easy to tell at a glance if the reeds are bad. You need to replace the gasket under the reed bank if you do this. There is really no other way to properly inspect the reeds. If you want to replace them, I's suggest Chris Carson reeds and hand lapping the reed blocks.

Well, I've got the carbs back on, and have a bleed line question- 2 lines were not connected, and I can't figure out where they go. One is coming off the choke plate at the bottom corner. The other one is coming off the barb fitting that is the center one right above the lower carb. The manual does not show where it goes, the picture is not complete, it just ends, and says "connect to bleed fitting in carburetor airbox" Not sure what that is. I can't find a diagram for this. Thanks a lot.

 

[Gary Lee]

Re: 1986 Merc 150 Black Max hard starting and overloading fuel

I mean, what is the airbox? Is it what the manual calls the choke plate? I cannot find anything in this Clymer manual that mentions an " airbox" other than this diagram which says the line goes to the "carb airbox" It I looked through the archives for correct routing of these 1/8 inch tubes/hoses and the only thing I could find was where someone had posted a diagram, but it was expired and I could not see it. The 1/8 inch hose that is coming off that middle barb fitting, (actually it is not in the middle, but is the middle fitting, but is right next to the port side other little bleed line fitting right above the lower carb) is a vacuum line for sure, when I started her up, I felt the end of the hose/tube, and it was sucking. I stuck it on the barb fitting coming out of the lower port corner of the "choke plate" as the manual calls it, but that's the only place I could see that it might go. The motor seemed to run good--on the ears only-have not taken it to the water yet. Anyway, if anyone gets what I am talking about here (sorry I have not explained it real well) I am open to suggestions as to where this vacuum line is supposed to be connected. Thanks a lot

 

[Faztbullet]

Re: 1986 Merc 150 Black Max hard starting and overloading fuel

Here is a bleed line routing for a the 5 hose routing which you may have. It sound line the recirc valves are bad or stopped up as this will cause fuel to puddle below reed block, causes bogging and rich running..

 

[Gary Lee]

Re: 1986 Merc 150 Black Max hard starting and overloading fuel

Thanks, everybody. I got everything back together and it runs much better. Starts 1000% better. The floats were not set correctly and one of the needle "clips" or whatever you call them, was off completely. The new gaskets did a lot of good, too, I think. Still smokes a good bit when idling for a long time. I think I will bypass the oil injection next. Thanks for your help.

 

[aussieflash]

Re: 1986 Merc 150 Black Max hard starting and overloading fuel

Air box covers the carbs.That bleed line connects to air box and sucks pooled fuel back for recirculation.
You may be running a little rich on oil.Your injection system is metered and can be adjusted at carb linkage.Though better too much than too little.Check your oil sensors are working and if so leave it alone.Ive heard more mishaps from premixers than malfunctioning oil injection........Im sure i put oil in it.

 

[Gary Lee]

Re: 1986 Merc 150 Black Max hard starting and overloading fuel

Air box covers the carbs.That bleed line connects to air box and sucks pooled fuel back for recirculation.
You may be running a little rich on oil.Your injection system is metered and can be adjusted at carb linkage.Though better too much than too little.Check your oil sensors are working and if so leave it alone.Ive heard more mishaps from premixers than malfunctioning oil injection........Im sure i put oil in it.

Thanks much. I was still a little confused about that one line. My manual (Clymer) calls that the chokeplate and not the airbox. I was pretty sure that that must be the spot for it, seemed too obvious, except that the line was much longer than it needs to be, so it threw me off. Thanks for the other info too. I will check those things. Thanks for the help--I need all I can get! I am a shade tree mech. at cars and motorcycles, but outboards are new to me. Only other one I had was a Merc. 50 hp, 1984--never had to do a thing to it to speak of--one sweet motor. Thanks again