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Mercury Blackmax 150 hp boggs out when in gear and trying to accelerate

D

duhn

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"Saturday I took my boat out f

"Saturday I took my boat out for the first time. When I went to accelerate, it only went up to 8 knots then stalled out.
Please help. Its the start of fishing season here!!!"
 
Old gas? Old plugs? Clogged fu

Old gas? Old plugs? Clogged fuel filter/vent/anti-syphon valve/tank pick-up? Air leak in one of the gas hoses?

Does pumping the fuel bulb help?

Would suspect a clogged carb(s) but you need to trouble shoot from the start....
 
"Thanks for the reply, New gas

"Thanks for the reply, New gas, new plugs, new fuel bulb. Havent had a chance to fire it up yet. I'll keep ya posted."
 
"Took the boat out this weeken

"Took the boat out this weekend and had the same problem. I did one other thing since my last post, I rebuilt the fuel pump. Next step is a link and sync then carb rebuild?"
 
"Devin, Check compression and

"Devin, Check compression and spark to all cylinders. If compression is even and spark is present, carbs are next culprit."
 
Compression checked out ok. L

Compression checked out ok. Lowest was 100 psi and the highest was 110 psi. I hooked up a timing light while it was running and there was a spark present on all plugs.
 
OK It is time to clean the car

OK It is time to clean the carbs. Get some kits that include the inlet needles and clean 'em up!
 
Update!
In the process of reb

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 thing hard 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. There was some water inside which let to so much corrosion that the main body and fuel bowl are not re-usable. I checked online and these parts are discontinued. I need 2 fuel bowls and one carb body. Any Ideas where I can get em?
 
"Well...........
I've tri

"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 more suggestions?"
 
Hey Chuck
I had a mechanic lo

Hey Chuck
I had a mechanic look at it last week while it was in the water. He said that the 3rd carb is not getting any gas. He's gonna work on it tommorow. I'll keep ya'll posted. Hope he gets it. the sand bass started spawning out here on the west coast!!!
 
"HEY ALL.I BELEIVE I FIXED MY

"HEY ALL.I BELEIVE I FIXED MY PROBLEM LAST NIGHT,I HAVE TO TRY IT ON THE WATER THOUGH.MY INSIDE POWER PACK WAS SHORTING OUT.IT HAD SPARK,STRONG SPARK AT THAT,BUT I BELEIVE IT WAS MISFIRING,CAUSING THE HIGH RPM,THEN LEADING TO THE BREAK UP AT 2800 RPM.LUCKILY I HAD TWO EXTRA PACKS LAYING AROUND TO TRY,AS IT WAS A LAST RESORT,AS THERE WAS REALLY NO EVIDENCE TO LEAD ME TO BELEIVE THE PACK WAS THE CULPRIT.THE HIGH RPM PROBLEM IS DEFINITLY FIXED,I WILL POST INFO ON THE WOT ISSUE AS SOON AS I MAKE IT ON THE LAKE TO OPEN IT UP."
 
"Well, the mechanic looked at

"Well, the mechanic looked at it and we put the boat in the water. Had the same problem. It appears that the bottom carb (or bottom cylinders) is not getting fuel. The fuel pump and carbs have been eliminated as being the problem. The mechanic is guessing that a seal inside the motor is 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. Whatcha think?"
 
"Deven, I would really like to

"Deven, I would really like to know what you find out. I have a 150 Black Max not firing on the bottom two cyl. even at idle, but I have fire one each. Means no fuel to fire. Sounds like similar issues."
 
"Deven and Robert, I have had

"Deven and Robert, I have had more than my share of the same problems. There is a great deal to trouble shoot between the Fuel system and ignition system. I have had a great deal of experience just recently with my Merc 150HP XR2 Black Max. Do either of you own a compression gauge. You need the kind that screws into the cylinder. Your compression should always be checked first. The compression should be read approx. 100. Let me know what you find out. Jimmy"
 
The only way I know of the che

The only way I know of the check sealing rings is through the bleeder hose fittings with a gauge. You can have all the compression in China in front of the piston and still not have a wiff of vacuum/pressure pulse behind it. That is what forces the fuel into the cylinder via the transfer system.
 
"Hey Jimmy, the compression c

"Hey Jimmy, the compression checked out ok.

Bandit, Where is this seal ring located? Someone had mentioned reed valves. They wouldn't be the same would they?"
 
I just joined and read your po

I just joined and read your posting. My 115 inline six is doing the same thing but i can get mine up and running if i pump the bulb. What would cause this. i did just about the same as you.
 
"if it picks up while priming

"if it picks up while priming the ball,that would sound like a fuelpump to me.have you changed that?they are very cheap to rebuild,just a few gaskets,diaghams,o-rings.goodluck"
 
Did anyone figure this out mines doing the same checked carbs checked spark took fuel pump off it’s pumping but not a great amount or at least I don’t think it’s a good amount I put my finger over the vacuum hole and didn’t feel anything was also wonder if I can plug that hole and electric pump it and I have one reed slightly open the rest closed I’m stumped
 
Dill pickle said:
Did anyone figure this out mines doing the same checked carbs checked spark took fuel pump off it’s pumping but not a great amount or at least I don’t think it’s a good amount I put my finger over the vacuum hole and didn’t feel anything was also wonder if I can plug that hole and electric pump it and I have one reed slightly open the rest closed I’m stumped
Click to expand...
I have an 85 merc 150 xr2 blackmax. It's a 6 cylinder motor, but has 2 send units each controlling 3 cylinders. At ide I had power to all 6 spark plugs, but put it under load and only 3 cylinders were firing. Likely one of your send units needs replaced. The engine actually is designed to run 3 cylinders at low throttle (no wake speed), and then engages the other 3 when you want to get on plane. Your other 3 cylinders aren't firing, thus the low speed
 
Nope----All the 6 cylinders have spark all the time !!!-----No such thing as a V-6 designed to idle on 3 cylinders !
 
Ok genius. I'll leave the guy with the problem this info because it likely will help him.

I had the same problem everyone else is describing. Out of the water engine ran fine with no load, revving and with it in gear. In the water the boat again seemed to be fine up to 7-10mph until pushing the throttle passed the halfway point when you can normally feel bank 2 engage. Anyone that actually has this motor knows there is an immediate change in exhaust tune and power when bank 2 engages. Then my engine would sputter and sound like it kept trying to kick, but it just wouldnt. It could cruise all day at that 7-10mph speed but couldn't get on plane.

These motors have 2 banks (3 cylinders each), each controlled by 2 send units. The send units are mounted right on top of each other on the back right of the engine if you are looking at it from behind. They are roughly 3-4" by 5". I had the faulty send unit ordered (over $400) and replaced. Back to running like normal.

Take your boat to someone that works on merc engines. They will back it into the launch still strapped down to the trailer and test your spark under load. My bet is you will only have power to 1 bank.

I have a picture of them on my motor I'm going to try to upload, but the website says it's having a problem uploading
 
V-6 Mercury motors have spark on all 6 cylinders all the time.------It is the inline 4 cylinder motors ( 2 +2 ) that run on the top 2 cylinders at idle.----Spark on all 4 all the time.-----The bottom 2 carburetors kick in at about 1800 RPM.
 
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