86 Mercury Blackmax 150 HP

[cannonford57]

Re: 86 Mercury Blackmax 150 HP

also was it a backfire or a sneeze from the carbs...not trying to be funny it does make a diff.

 

[Kev144]

Re: 86 Mercury Blackmax 150 HP

I had a similar issue which turned out to be a stator

 

[duhn]

Re: 86 Mercury Blackmax 150 HP

I have a mechanic looking at it now. We took it in the water for him to examine it. He knew right away when it was started that there was a problem. He started sticking his fingers in the carbs, and said that the bottom carb was not getting any fuel. He took the carbs apart and said the rtv sealant that was used on the elbow connectors that supply the carb had come off and clogged the jets.
I'll keep ya'll posted after he gets back together.

 

[duhn]

Re: 86 Mercury Blackmax 150 HP

Well, The mechanic and I put the boat in the water earlier this week. The results were the same. The motor was sneezing, it appears that the bottom carb (or bottom cylinders) is not getting fuel. With fuel pump and carbs eliminated as the problem, my mechanic is guessing that a seal inside the motor has gone bad. I cant remember which seal he called it. He thinks that the bad seal is causing the fuel to get forced into the next cylinder instead of compressing it. This is something that would warrant a rebuild, huh?

 

[j_martin]

Re: 86 Mercury Blackmax 150 HP

Swap the bottom carb with one of the others. If the problem moves, swap out the mechanic.

Crankshaft seal ring failure is a big stab in the dark. They either break in the first 3 rounds, or live forever.

How do the reeds look?

hope it helps
John

 

[LubeDude]

Re: 86 Mercury Blackmax 150 HP

I had a similar problem with my old 150, it turned out to be reeds. Try this, you have to have someone else in the boat to hold the wheel. While giving the engine fuel, push in the choke at the same time. It's a bit awkward, but you can do it!

The reeds eventually wear down the cages and they leak which causes the problem you are facing.

 

[duhn]

Re: 86 Mercury Blackmax 150 HP

Funny you mentioned reeds. I was just reading up on them. That is my next area to invesitgate.

 

[j_martin]

Re: 86 Mercury Blackmax 150 HP

Funny you mentioned reeds. I was just reading up on them. That is my next area to invesitgate.

Reeds on a V6 are quite easy to deal with. After the carbs are off, remove a few bleed lines, and unbolt the reed plate and remove it with all the reed cages and reeds at one time. Inspect at that point, and if all is well, reinstall replacing only the reed plate and carb base gaskets. If not, you can do the needed maintenance on the workbench.

Mark the bleed lines when you take them off. Routing is critical, and there are several possible combinations, but only one for your engine. It's a lot easier to tape a label on the lines than to read up on it and figure it out later.

hope it helps
John

 

[duhn]

Re: 86 Mercury Blackmax 150 HP

Hey John,
I have the carbs off and can see the reeds. What is it that I am looking for? The manual states that there must not be more than .020" of clearance. All of them are touching except for 2 of them under the bottom carb. I can't get an accurate measurement unless I remove the reed block, which will require alot of work. Since there are 2 reeds not touching, is it worth it to replace them????

Devin

 

[j_martin]

Re: 86 Mercury Blackmax 150 HP

Hey John,
I have the carbs off and can see the reeds. What is it that I am looking for? The manual states that there must not be more than .020" of clearance. All of them are touching except for 2 of them under the bottom carb. I can't get an accurate measurement unless I remove the reed block, which will require alot of work. Since there are 2 reeds not touching, is it worth it to replace them????

Devin

Once the carbs are off, it's only bleed hoses and a handful of bolts to pull the reed block. You really can't inspect them unless you pull the block off.

You have noticed a variation with the bottom set. You should look into it.

Most reeds lay down almost perfectly on the block. Even then, the finish on the block can be critical to a good idle. They would affect low rpm performance for sure.

Have you done any fuel pressure testing?
Did you swap the carbs around as I suggested?

If you decide to replace the reeds, throw in a set of aftermarket fiberglass reeds (Boyesen or others). They perform better, and less expensive than stock, and if they fail, get digested by the motor with little damage, where the steel ones usually cause mortal damage. Hand lap the reed cages so they have a real good seal.

hope it helps
John

 

[duhn]

Re: 86 Mercury Blackmax 150 HP

Yeehaw!!!!!!!
I got it fixed!!
Kind of a long story.
I had given up on fixing this motor and started looking for a replacement motor. I tried a different stator and coils Sunday with the same results. While the motor was running, I started pulling off spark plugs off one at a time. removing the top 4 stalled the motor, but removing the bottom 2 had no affect what so ever. That pointed the problem back to the bottom #3 carb. I then removed the jet plug from the bottom of the fuel bowl on carb #3 and nothing came out. I then pulled the jet plug on carb #2 and gas came out. I then pulled the bottom carb off and carefully disassembeled it while leaving the fuel inside of the bowl. There was plenty of fuel in the fuel bowl. The fuel bowl has a tube in the middle that the needle jets pick up the fuel from. There was no fuel in this tube. I then dumped the fuel and tried to figure out how the fuel is supposed to get in to this tube. I couldn't figure it out so I took apart carb #2. Carb #2 has a hole at the base of this tube that gets fuel from the bowl. Carb #3 did not have this hole. I then started poking a paperclip where this hole is supposed to be and what do you know? It started flake away. I then cut the paperclip in half and bent the end 90 degrees 1/8" from the end and put in my drill and kinda used it like a plumbers snake to clean it out. GENIUS!! Unless the two carbs were put next to each other and inspected, there is no way that anyone could tell that there is supposed to be a hole there. It was so clogged that it looked like someone filled it with bondo, sanded it and painted it to match the rest of the bowl. Put it all back together and it ran great.

Today I took it in the water and it ran like a champ!!

Sorry for the long post.......perhaps others can learn from this experience.

It is definetly much better being a boat owner that has a boat that works.

Thanks for all your help

Devin

 

[thaphillips]

Re: 86 Mercury Blackmax 150 HP

I got this exact same motor and had similar problems when I first got it. I have never been one to use additives, but I was talking to my fiberglass repair tech and the engine tech came by so I described my problems. He suggested I try a product called Sea Foam before rebuilding the carbs. Low and behold it worked.

Like I said I don't normally use additives, but I am a believer in Sea Foam. It's easier than rebuilding the carbs.

 

[starcraft1982]

Re: 86 Mercury Blackmax 150 HP

Very good to hear you got her going.However,Im a little perplexed as to how not having spark on bottom two plugs pointed you back to the carb!?!?No spark would mean electrical issue,not fuel.Just a little curious,thats all.

 

[starcraft1982]

Re: 86 Mercury Blackmax 150 HP

nevermind.Its late and brain isnt functioning properly,i guess!