86 Mercury Blackmax 150 HP

[duhn]

I took my boat out for the first time today. The motor runs good in neutreal and in gear at idle. As soon as I tried to open it up, it would stall out, and have a diffucult time to restart. Please help!!

 

[frozenokie]

Re: 86 Mercury Blackmax 150 HP

Mine did this too. Has the motor been sitting for a while? Have you recently done any changes to the engine like cleaning carbs or anything? Are you able to slowly push the throttle down and not have the bogging problem?

I found on my 115 that the problem was the spark plug prongs, where it goes into the coil pack, had lost good contact. I knew this from pulling the plugs (which were brand new) and the third cylinder still looked brand new while the others clearly were firing.

I spread out the prongs on the spark plug wire to ensure contact within the coil pack. After that it was fine.

It could be other things too. For instance, the floats in the carbs could need adjustment, incorrect ignition timing, a failing or leaky fuel pump, or I have found in past problems, a bad fuel priming bulb, clogged main jets.

 

[duhn]

Re: 86 Mercury Blackmax 150 HP

Thanks for your reply.
Yes, the motor has been sitting for a year. No I haven't done anything to the carb. No, I am not able to push on the throttle slowly to avoid the bogging. Max speed is about 7-8 knots.

When I got home, I tried to duplicate the same symptoms. I was only able to do that when I put the motor in a trash can full of water. Otherwise, it ran just fine with the muffs on. It appears that when ever there is a load put on the motor, that is when it is bogging out. I hope I dont have an outboard that doesnt like water!!!

I'm gonna try the things you mentioned starting with the primer bulb then the spark plugs and its connections.

If the problem is in the carburator, is it difficult to adjust the float??

 

[frozenokie]

Re: 86 Mercury Blackmax 150 HP

I wouldn't say that it's difficult, but you have to be precise in getting all the floats set exactly the same. The only other thing that comes to mind is a prop that is too high a pitch for the boat and motor. I'm still thinking of things...

 

[jscgdunn@telus.net]

Re: 86 Mercury Blackmax 150 HP

HI,
I had exactly the same thing...it was due to the engine being too deep in the water...exhaust was full of water and couldnot clean out...be sure your boat is not overloaded at rear.

 

[duhn]

Re: 86 Mercury Blackmax 150 HP

Interesting! never paid any attention to that. I'll have to look at that the next time It's in the water.

Thanks

 

[jcskeeter]

Re: 86 Mercury Blackmax 150 HP

Is that true jscgdunn about a motor being to deep in the water? I notice that with mine when I have the livewells full, thus making the motor sit deeper, I can't get up as fast. I just thought it was because it was an older motor that lost some of it's lower end. Oh yeah boat is a 89 18'6" skeeter with 89 mariner 175.

 

[j_martin]

Re: 86 Mercury Blackmax 150 HP

Is that true jscgdunn about a motor being to deep in the water? I notice that with mine when I have the livewells full, thus making the motor sit deeper, I can't get up as fast. I just thought it was because it was an older motor that lost some of it's lower end. Oh yeah boat is a 89 18'6" skeeter with 89 mariner 175.

Actually, there is some exhaust relief that should let it idle. As soon as you start to add power, the water flowing by the prop tends to pull the exhaust out. At speed, the relief ports just make a little noise.

The carb'd v6's are, however, sensitive to being level to idle. It varies from boat to boat, but you can carry them too high, and you can bury them too deep, but I think keeping the carbs level is more important than depth.

When the livewells are full, you have a lot of added weight, which will make it harder to get going, and also considerably lower your top speed. It's just the weight that makes a difference. If you're proped for top speed empty, it might actually struggle some to get up with the wells full.

hope it helps
John

 

[duhn]

Re: 86 Mercury Blackmax 150 HP

After changing the plugs, bulb primer, cleaning all the spark plug wire connections, fresh gas, and rebuilding the fuel pump, I still have the same problem.
To clarify jscdunn's comment, no the exhaust is not under water.
I guess the next thing do is a link and sync., and possibly rebuilding the carburators? What do you think?

 

[Chris1956]

Re: 86 Mercury Blackmax 150 HP

Lets start with the basics. Put a timing light on each plug wire at idle on the flusher. If all are getting spark, check the compression of all cylinders. It should be at least 100PSI, and very even across all cylinders. it these tests pass, the carbs are next. Clean each carb completely, install new gasket kits and adjust the floats and idle mixture screws as directed by a service manual. You will need to make the final adjustment to the idle mixture on the water. This can be a bit tricky, but here is a trick. Warm the motor, put it in gear (if you can) at idle. Now adjust the motor to run smoothest and fastest, buy adjusting each needle a little bit at a time. Now try to accelerate. if the motor stumbles, open the top carb screws 1/8 turn on each barrell. Try to accelerate. if the motor still stumbles, open the mid carb screws 1/8 turn. try to accelerate again. if not good, open the lower carb screws 1/8 turn and try again. Repeat if necessary top-mid-lower carb, in that order. Eventually, you should have a reasonable idle and smooth acceleration.

 

[xxturbowesxx]

Re: 86 Mercury Blackmax 150 HP

check the coil packs.. maybe someone with more experience can tell you how but i would think you could run the engine carefully (with a non metalic object) remove the spark plug wires on one side then the other and check for spark..i had the same symptoms as you and that was my problem on a 88 mariner 150hp

 

[duhn]

Re: 86 Mercury Blackmax 150 HP

I put a timing light on all the plug wires and I have a steady spark on all. I had already done a compression check. The lowest was 100 psi and the highest was 110 psi. I think that passed the compression test.

I guess it's time to rebuild the carbs. I'll update ya'll when that is done.
Thanks for all the help.

 

[Phunahm]

Re: 86 Mercury Blackmax 150 HP

Ive been threw all that a while ago with my 86 150XR2 carb rebuild ,ignition,etc etc etc the dealer couldnt figure it out . I ended up changing my prop from a 14 1/4x 24 to a 13 3/4 x24 4 blade problem went away till this day still dunno why it started action up.....

 

[duhn]

Re: 86 Mercury Blackmax 150 HP

Update!
In the process of rebuilding the carbs. My motor happens to have 3 of em. The first one I rebuilt was real easy. the only hard thing was dishing out 85 bucks times 3 for the rebuild kits. The second one went ok except the main jet broke off inside the bowl. The third one was my problem all along. This rebuild did not go well at all. There was water inside and it led to so much corrosion that the main body and bowl is not re-usable. I checked online for new parts. The carb body and the fuel bowl are discontinued. I need 2 fuel bowls and one carb body. Any ideas where to get em? I hope I dont have to trash the whole motor because I cant get some carburator parts.

Please help!!!

 

[duhn]

Re: 86 Mercury Blackmax 150 HP

Well...........
I've tried everything. The carbs have been rebuilt. I was confident that this would solve the problem. The 3rd carb was clogged, stuck, and full of crud.
Todays boat ride resulted in another disappointing one. It's still the same as before.

Here is a list of things that I have done.

Fresh fuel
New spark plugs
Rebuilt fuel pump
Timing
Compression Check (checked out ok)
Rebuilt all 3 carbs.
New fuel lines inside and out
New primer bulb.
Link and sync.

I did notice a couple of times when trying to start that there was a back fire from the carbs. The other thing that I tried was opening the butterflys on the carbs by hand. It just wanted to stall out. It still sounds like a lack of fuel problem.


any suggestions?

 

[CharlieB]

Re: 86 Mercury Blackmax 150 HP

Carbs are not clean yet.

No accelerator pump on a two stroke, the idle mix must be just fat enough that the motor will accelerate under load, best idle on the garden hose is too lean and needs almost another 3/4 turn out on the idle mixture screws.

Some carbs do not have idle mixture screws but have idle air bleeds and idle fuel jets, BOTH MUST BE absolutely clean. Missing even one and the boat will not accelerate.

 

[duhn]

Re: 86 Mercury Blackmax 150 HP

Looks like I have ya'll stumped.

 

[j_martin]

Re: 86 Mercury Blackmax 150 HP

Looks like I have ya'll stumped.

I resemble that.!!!

Have you formally checked out the fuel system, like with a vacuum gauge or a pressure gauge. Best bet would be a pressure gauge put on the carb fuel fitting that now has a plug in it. If it stays over a couple of pounds, yer getting fuel.

Next thing:
Have you checked the spark with a spark gap, or just a plug. A 1/2 inch spark in open air will drop down to about 1/8 inch under compression.

Next thing:
to do would be to rig a timing light on each plug wire, one at a time, and seeing if the spark stays steady when you throttle up on the lake.

You're missing something, either spark or fuel in one or more cylinders, under load. Trick is to systematically isolate it.

hope it helps
John

 

[mwoodard]

Re: 86 Mercury Blackmax 150 HP

I am having teh EXACRT same problem.

Carbs have beed rebuilt, fuel pump rebuilt, fuels lines replaced, fuel filter replaced, ignition wires replaced, plugs replaced, coils replaced. I am at wits end myself. With ears on it will rev right up in neutral or in gear. On the water it will rev right up in neutral but in gear it gets to 1000-1100 RPM and just craps itself.

I am bout ready to idle it out to the middle , pull the plug, and have a leisurely swim back in. 1989 Mercury 150.

 

[cannonford57]

Re: 86 Mercury Blackmax 150 HP

assuming u have access to a timing light,on a flusher,start engine,disconnect throttle cable from linkage,slowly advance throttle no more than 2500 rpm watching each cyl.with the timing light attached make sure the spark doesent drop out between 1800 and 2500 rpm...if so u could have a stator issue