Trouble getting full power out of 150 black max

[TBSLawnEngine]

I have a Merc 150 blackmax on my bass boat and am having trouble getting full power out of the engine. It alwasy starts up with little to no problem and revs up quickly and to full power when I have the throttle in the warm up position...prop not engaged. When I engage the prop it will drive around fun put when I put the throttle down to take off it bogs at times and I can sometimes get it to take off with a little moving around throttle and suddenly it takes off. I can run it at full speed accross the water for a min or so and it seems to loose power and I have to pull the throttle back or it will die. After it dies I can get it to start right back up and it will act the same again. I'm a little stumped and am not sure where to procede. I thought it was a cable or carb problem but it doesn't explain why it idles right up with the prop not engaged. Also I don't understand how it can suddenly come to life and take off run like a champ and suddenly loose power. Ideas?

 

[Barnacle_Bill]

Re: Trouble getting full power out of 150 black max

What year is it?

 

[j_martin]

Re: Trouble getting full power out of 150 black max

The high speed part of that sounds like fuel starvation, which is a whole subject all by itself.

One of the problems with fuel starvation is it can overheat one or more cylinders and cause serious damage.

The low speed part of your problem sounds like that may have already occurred.

Do a compression test. If all is good, you haven't hurt anything......yet.

Then, don't ever try to run that engine at speed when it's balking. If it don't want to pony up, don't push it.

Solve the fuel problem, which can be anything from too much oil in the fuel to a pinhole in the pickup tube to bad hoses to fuel pu......well, you get the idea.

Some of these could load it up at idle, and that problem could "fix itself". If that problem is then not solved, it is a separate issue.

It still would help to know more about the exact engine we're talking about.

hope it helps
John

 

[TBSLawnEngine]

Re: Trouble getting full power out of 150 black max

What year is it?

I beleave the engine is a 1986 model but I'll double check

 

[TBSLawnEngine]

Re: Trouble getting full power out of 150 black max

The high speed part of that sounds like fuel starvation, which is a whole subject all by itself.

One of the problems with fuel starvation is it can overheat one or more cylinders and cause serious damage.

The low speed part of your problem sounds like that may have already occurred.

Do a compression test. If all is good, you haven't hurt anything......yet.

Then, don't ever try to run that engine at speed when it's balking. If it don't want to pony up, don't push it.

Solve the fuel problem, which can be anything from too much oil in the fuel to a pinhole in the pickup tube to bad hoses to fuel pu......well, you get the idea.

Some of these could load it up at idle, and that problem could "fix itself". If that problem is then not solved, it is a separate issue.

It still would help to know more about the exact engine we're talking about.

hope it helps
John

I did a compression test and the figures for 5 of the cylinder were 110 ball park and one had 80. I already replaced the fuel lines from the tank to the fuel pump. Not sure if I did them any further. I'll have to look and post up. I have always mixed my fuel 50:1 mix is that too much oil? I'll run a compression test again this morning and check to see if I replaced any more lines. You mention a low speed part?? I have no problem keeping it running smoothly at low speed its just when I want to take off suddenly.

 

[j_martin]

Re: Trouble getting full power out of 150 black max

I did a compression test and the figures for 5 of the cylinder were 110 ball park and one had 80. I already replaced the fuel lines from the tank to the fuel pump. Not sure if I did them any further. I'll have to look and post up. I have always mixed my fuel 50:1 mix is that too much oil? I'll run a compression test again this morning and check to see if I replaced any more lines. You mention a low speed part?? I have no problem keeping it running smoothly at low speed its just when I want to take off suddenly.

I threw in the bit about too much oil because it's a common problem. Kinda like kids figure a loud muffler makes a pick-m-up faster. People notice that racing motors use more oil, so they think that's a good thing. Weird thing is if the engine isn't set up for it, more oil actually can lean out the mix and burn down the power head.

80 on one cylinder is not a good sign. Try de-carboning it and see if it comes up. Otherwise you might have some piston or cylinder damage. That often occurs when an engine is run lean.

Back to the problem.
1. Engine identity. Mercury called everything over 150 ponies and painted black "black max." It could be a 2.0 or 2.4 if it's a V6. Inline 6 is before my time. Each engine type has it's own nuances.

2. I got my XR4 discounted because it had a high speed balk in it. I had to put a pressure gauge on it to track down the problem. I found:
Junk in fuel tank
Loose (air leak) pickup tube
bad fuel lines
Bad primer line. (New aftermarket bulb and line, wasn't up to par)
fuel pump warped valves
fuel filter plugged (multiple times)
Floats set wrong
and finally, the aftermarket plastic bayonet connector would not pass enough fuel.

3. Idle loading up is usually either idle mix or bleed valves. The fittings on the reed plate behind the carbs with the little lines on it are bleed valves. That engine is sensitive to leveling. If you try to idle it a long time with negative trim, it'll normally load up. Trim it up a bit, and all is cool. Just don't forget to tuck it in when you blast off, or it could hop a bit. (At least on my hot rod bass boat.) At this point I'd guess it's just this operational detail that's getting you.

Another critical item on hole shot is the correct setup of link-n-sync. If the carbs open up at the wrong point, she'll bog. If any shade tree (certified or not) that doesn't know what a link-n-sync is but thinks they know everything has "adjusted" it, this is the problem.

hope it helps
John

 

[TBSLawnEngine]

Re: Trouble getting full power out of 150 black max

I threw in the bit about too much oil because it's a common problem. Kinda like kids figure a loud muffler makes a pick-m-up faster. People notice that racing motors use more oil, so they think that's a good thing. Weird thing is if the engine isn't set up for it, more oil actually can lean out the mix and burn down the power head.

80 on one cylinder is not a good sign. Try de-carboning it and see if it comes up. Otherwise you might have some piston or cylinder damage. That often occurs when an engine is run lean.

Back to the problem.
1. Engine identity. Mercury called everything over 150 ponies and painted black "black max." It could be a 2.0 or 2.4 if it's a V6. Inline 6 is before my time. Each engine type has it's own nuances.

2. I got my XR4 discounted because it had a high speed balk in it. I had to put a pressure gauge on it to track down the problem. I found:
Junk in fuel tank
Loose (air leak) pickup tube
bad fuel lines
Bad primer line. (New aftermarket bulb and line, wasn't up to par)
fuel pump warped valves
fuel filter plugged (multiple times)
Floats set wrong
and finally, the aftermarket plastic bayonet connector would not pass enough fuel.

3. Idle loading up is usually either idle mix or bleed valves. The fittings on the reed plate behind the carbs with the little lines on it are bleed valves. That engine is sensitive to leveling. If you try to idle it a long time with negative trim, it'll normally load up. Trim it up a bit, and all is cool. Just don't forget to tuck it in when you blast off, or it could hop a bit. (At least on my hot rod bass boat.) At this point I'd guess it's just this operational detail that's getting you.

Another critical item on hole shot is the correct setup of link-n-sync. If the carbs open up at the wrong point, she'll bog. If any shade tree (certified or not) that doesn't know what a link-n-sync is but thinks they know everything has "adjusted" it, this is the problem.

hope it helps
John

The boat is a 150 Black Max V6 all I could find on it was the serial number 62213985.

Alright went out and ran it for a while at idle to warm it up (started right up with no problem) shut her down and did the compression test on each cylinder they were 110,110,110,110,90,110. Things I noticed is that there seems to be a lot of gas accumulated under the carb and in the cover. All the plugs were went when I pulled them. I double checked the fuel lines and I replaced all off them except fort he section from the engine side of the fuel hook up on the motor to the fuel pump.... runs under the bottom carb. Not sure if the gas accumulation if from trimming the motor up in transport or not??? The engine idles with muffs on at 1900-2000 rpm. I did notice that once in a while when idling it would send a puff of smoke but didn't seem to effect running. What is the function of the little hoses that run from each cylinder back to the carb? They look pretty old but I'm not sure of their function. Should I pull the head to check out the cylinder? Do you have to remove the whole power head to install new rings and/or pistons?

 

[j_martin]

Re: Trouble getting full power out of 150 black max

That engine should idle smoothly at under 1000 rpm on the cuff, at under 700 in gear in the water. It's not idling, it's racing.

The little lines are bleed lines. If they are bad, it won't idle slow like it should. The fittings near the carbs that they are connected to are actually check valves, and can be tested easily with a short piece of bleed line and a plastic syringe like used for hypodermic needles. The purpose of the bleed hose is to pull excess fuel pooled behind the carb and send it to the opposite cylinder to be burned.

Sometimes carbs spill a little fuel if tilted all the way up. Level the engine and squeeze the primer bulb firmly, not white knuckle. If it holds for a time, and no gas runs out of any carburetors, the needle valves are fine. If not, fix it.

hope it helps
John

 

[TBSLawnEngine]

Re: Trouble getting full power out of 150 black max

I think the primmer bulb is ok. I replaced it when I did the fuel lines and it stays hard. I've never had to reprime it get it started once it was running for the day. I think I'll replace the vacume lines since I beleave they are original. I'll pull the carbs and clean them out. What is "decarb". I beleave you mentioned doing to see if it help with my one cylinder with low compression. Could the reeds be bad causing my running issue? Years ago I had a jetski and it had a issue with the reeds that caused it to run poorly not sure if they cause the same effect on outboards or not. As for link and sync. Is it something I can do myself or do I have to take it to a dealer? Thanks for all your help

 

[j_martin]

Re: Trouble getting full power out of 150 black max

I think the primmer bulb is ok. I replaced it when I did the fuel lines and it stays hard. I've never had to reprime it get it started once it was running for the day. I think I'll replace the vacume lines since I beleave they are original. I'll pull the carbs and clean them out. What is "decarb". I beleave you mentioned doing to see if it help with my one cylinder with low compression. Could the reeds be bad causing my running issue? Years ago I had a jetski and it had a issue with the reeds that caused it to run poorly not sure if they cause the same effect on outboards or not. As for link and sync. Is it something I can do myself or do I have to take it to a dealer? Thanks for all your help

Decarboning the engine
http://forums.iboats.com/showthread.php?t=158076

Reeds definitely are important. It's possible a piece of reed came off and boogered the low cylinder. That's one reason why when we replace reeds, we usually go with fiberglass. They're more "digestible" Good news is the reeds are all mounted on one big plate behind the carburetors. Once the carbs are off, it's only bolts and bleed lines to get the reeds off. It's worth doing if yer that far into it.

Link-n-sync is definitely doable. It's in the Mercury manual. You need a dial indicator or depth gauge (I use a 12 buck Harbor Freight digital caliper) set up on a spark plug hole, and a timing light.

go for it.
John

 

[sschefer]

Re: Trouble getting full power out of 150 black max

The puffing you mention is from too much fuel and not enough air. Probably just one cylinder and could be reeds, a bad bleeder check valve or even a stuck float. John has you on the right track.

You can check the reeds with a standard crankcase pressure check using a fuel pressure gauge and checking the pressure according to service manual procedures. If you don't have one of those yet you should probably get one since you'll need torque specs, etc., if you need to replace a set of reeds.

I wouldn't rule out a carb rebuild with new floats, needles and seats. Once you do the pressure test you'll know for sure. Most will tell you that you don't need to replace the needles and seats but the one time I didn't I ended up tearing the carbs back apart again.

As a side note - If you find you have bad reeds on one cylinder, you may want to consider replacing all 6 sets. Yours are vertical reed blocks and you probably won't see a big performance enhancement with anything other than stock reeds.

However, Chris Carson Marine makes a set of reasonably priced plastic reeds for your engine that may improve your idle and throttle response. You can find him at http://www.chriscarsonmarine.com/ if your interested. Great guy and quick to ship. I'm running them in my 2.0L and I like them.

Please notice that I used "might" and "may" a lot. The results will vary depending on the overall condition of the engine.

 

[TBSLawnEngine]

Re: Trouble getting full power out of 150 black max

Decarboning the engine
http://forums.iboats.com/showthread.php?t=158076

Reeds definitely are important. It's possible a piece of reed came off and boogered the low cylinder. That's one reason why when we replace reeds, we usually go with fiberglass. They're more "digestible" Good news is the reeds are all mounted on one big plate behind the carburetors. Once the carbs are off, it's only bolts and bleed lines to get the reeds off. It's worth doing if yer that far into it.

Link-n-sync is definitely doable. It's in the Mercury manual. You need a dial indicator or depth gauge (I use a 12 buck Harbor Freight digital caliper) set up on a spark plug hole, and a timing light.

go for it.
John

Well I decarbed the engine today and there was plenly of black crap that came out and it seemed to run a lot smoother but still not quite right. I sprayed a little more deep creep in all the plug holes tonight and am going to let it soak over night. Hopefully in the next few nights I'll have enough time after work to pull the carbs and reed block to check them out.

 

[TBSLawnEngine]

Re: Trouble getting full power out of 150 black max

The puffing you mention is from too much fuel and not enough air. Probably just one cylinder and could be reeds, a bad bleeder check valve or even a stuck float. John has you on the right track.

You can check the reeds with a standard crankcase pressure check using a fuel pressure gauge and checking the pressure according to service manual procedures. If you don't have one of those yet you should probably get one since you'll need torque specs, etc., if you need to replace a set of reeds.

I wouldn't rule out a carb rebuild with new floats, needles and seats. Once you do the pressure test you'll know for sure. Most will tell you that you don't need to replace the needles and seats but the one time I didn't I ended up tearing the carbs back apart again.

As a side note - If you find you have bad reeds on one cylinder, you may want to consider replacing all 6 sets. Yours are vertical reed blocks and you probably won't see a big performance enhancement with anything other than stock reeds.

However, Chris Carson Marine makes a set of reasonably priced plastic reeds for your engine that may improve your idle and throttle response. You can find him at http://www.chriscarsonmarine.com/ if your interested. Great guy and quick to ship. I'm running them in my 2.0L and I like them.

Please notice that I used "might" and "may" a lot. The results will vary depending on the overall condition of the engine.

I have a Clymers service manual and was paging though it last night a little. Will it have all the information for linc and sync or do I need to get a Merc Manual

 

[sschefer]

Re: Trouble getting full power out of 150 black max

I have a Clymers service manual and was paging though it last night a little. Will it have all the information for linc and sync or do I need to get a Merc Manual

The Clymer should cover it but for sure the Merc Service Manual does.

 

[TBSLawnEngine]

Re: Trouble getting full power out of 150 black max

Been a while since I posted up. I got new vacume line to replace the lines going from the intake port to the cylinders. The ones I pulled didn't allow air to pass. Planning on doing a few things tommorow between meals since I'm off. I'll postup my findings.

 

[j_martin]

Re: Trouble getting full power out of 150 black max

Been a while since I posted up. I got new vacume line to replace the lines going from the intake port to the cylinders. The ones I pulled didn't allow air to pass. Planning on doing a few things tommorow between meals since I'm off. I'll postup my findings.

That'll be significant.

John

 

[TBSLawnEngine]

Re: Trouble getting full power out of 150 black max

Well I replaced all the vacume lines from the cylinders to the intake ports. About 1/2 didn't allow air to pass. One thing I did notice was that the number 5 cylinder didn't have a vacume port I could find or a line running from it. Am I missing something? Thought it was kinda ironic that its the same cylinder that I have a lower compression reading. Over the weekend I plan to pull the carbs hopefully and clean them out as well as check the reeds to see if any of them are broken.

 

[TBSLawnEngine]

Re: Trouble getting full power out of 150 black max

Well pulled the carbs today. And they are currently soaking in carb dip. When I split them open i really found nothing. Everything looked clean with the exception being under the top cover of the carb. In the carb body it seemed to have a accumulation of 2 stroke oil not sure if thats normal or not. All the foats are intact and moved freely and the needle and needle tips were clean. Should I replace the floats anyway and/or do they need adjustment for needle seating. I looked at all the reeds through the intake ports and they are all there and none of them seem bent more that the others. Do I need to pull the entire intake to further look at the reeds? I was hopeing to find a dirty carb and at least a broken reed to explain my one cylinder with lower compression. Also when I pulled the bowls off the carb none of them had anything but a few drops of gas in them. I would have expected they would have been full of fuel. Neighbor was over and said maybe my whole problem is a clogged fuel filter starving the engine of fuel. I've never seen a inline filter anywhere. Is there one internally somewhere like in the fuel pump?