Mercury 150 not performing well under load and drinking gas.

[karnage]

I bought a boat with a Mercury 150 Blackmax on it awhile ago, the seller said the carbs needed to be cleaned. Ill save the majority of the story and jump to where I have taken the carbs apart to find they're very clean and floats look and move fine, I've bought new plugs, and ran some seafoam through it. The engine runs pretty well at idle around 1000rpm, and I can rev it in and out of gear without any load to 6000 plus rpms. I can get it to idle in gear, and give it a hair a throttle (I think it's worth noting I have an aftermarket hot foot) but once it gets to 1-2000 rpms it doesn't want to take anymore and bogs out. In my multiple trips of taking it out and testing it, there was one trip where I put it in gear and slammed it to the floor and it slowly got up onto plane with a top speed of 42 trimmed up. But with my trip today after buying new plugs and inspecting the carbs, it runs better with no load, but does not want to run under load in the water. I did get my foot to the floor at a solid 1900 rpms with the motor trimmed up but most of the time couldn't give it more than a little throttle. Another big problem is it absolutely drinks gas. The engine has had an oil injection delete and I premix my fuel and put it into the cell. It went through like 4 gallons today and I never even got it on plane, similar story to the trip I got it on plane. The cell will hold fuel, but something with the engine is drinking it. All 6 cylinders are getting spark, all fuel lines are tight, and I didn't mess with anything tuning related on the carbs when reinstalling them. Are the carbs just bad?. I'm absolutely lost, any word of advice will be greatly appreciated.

 

[merc850]

"without any load to 6000 plus rpms" is not recommended, maybe you damaged it.

 

[karnage]

"without any load to 6000 plus rpms" is not recommended, maybe you damaged it.

It was for a short period of time in the water. The engine would bog out from the ramp, before I ever revved it in neutral.

 

[jimmbo]

Carbs are part of it, so is Spark Advance. It the timing advancing as the throttle lever is pushed? Is the Primary Pickup Timing Correct? Its the Max Advance set correctly
Back to the carbs, are all fully closed at Idle?
Are the floats set properly?
Are the idle mixture screws(if the carbs have them) set properly.
Forget all of the above for the moment
What are the compression numbers?
Is every Cylinder getting a Spark that can jump a 3/8" gap?
If compression and spark are good, then go back to the top of my post

 

[karnage]

Carbs are part of it, so is Spark Advance. It the timing advancing as the throttle lever is pushed? Is the Primary Pickup Timing Correct? Its the Max Advance set correctly
Back to the carbs, are all fully closed at Idle?
Are the floats set properly?
Are the idle mixture screws(if the carbs have them) set properly.
Forget all of the above for the moment
What are the compression numbers?
Is every Cylinder getting a Spark that can jump a 3/8" gap?
If compression and spark are good, then go back to the top of my post

Great questions, thanks for the response. My buddy said the timing arm thing was moving with the throttle. The plug wires were jumping to the plugs pretty far, I think they're fine. I haven't been able to check compression yet. The carbs do appear to be completely closed at idle. I assume the floats are set properly, they were pretty level with the top of the bowl and seated well, none of them stood out as off. I'm not the most knowledgeable person, I honestly have no clue if the Primary Pickup Timing is Correct or the Max Advance. The previous owner had the boat sit for two years and as far as I know it ran well previous.

 

[jimmbo]

Motors always ran/run great till they don't.
Well since parts are described as things, and neither you or your friend appear to be familiar with these engines, and what makes them tick. I suggest you don't go near them with tools that can adjust things. Assuming things has lead to many of these engines being adjusted way out to where they never run right
Get the CORRECT Factory Service Manual for that engine, and study it until you can recite it.
BTW, the Mercury V6 is one of the finest Outboards ever made. Well engineered, they are hard to beat, and not just in top speed

 

[Scott Danforth]

Nowhere do you post compression numbers. Start there

Then check the contents of the fuel filter for pure fuel

 

[karnage]

Motors always ran/run great till they don't.
Well since parts are described as things, and neither you or your friend appear to be unfamiliar with these engines, and what makes them tick. I suggest you don't go near them with tools that can adjust things. Assuming things has lead to many of these engines being adjusted way out to where they never run right
Get the CORRECT Factory Service Manual for that engine, and study it until you can recite it.
BTW, the Mercury V6 is one of the finest Outboards ever made. Well engineered, they are hard to beat, and not just in top speed

I appreciate the response. I'm not looking to become a professional with these things but I definitely want to learn and get better. I'll go get a compression gauge tomorrow. As for getting an om manual, since you seem very knowledgeable I figure ill ask you a question about identifying my motor model. The little serial number label on the back side of motor reads "0c267625" which a serial number lookup tells me it's a v-200, but the cover, in the least says its a 150 blackmax. The numbers on the block behind the timing arm read "2 2084". So I believe that means its a 1984 but I'm not positive its a v150 or v200, so I'm not sure which manual to look for. I'm sorry I'm a dumbass.

 

[karnage]

Nowhere do you post compression numbers. Start there

Then check the contents of the fuel filter for pure fuel

I will get compression numbers tomorrow and for sure get back to this forum, as for the fuel filter contents, I'm not even sure where it is. I know there's a little cylinder that fuel lines connect to beside the carbs but I'm not sure if that's where its located.

 

[Scott Danforth]

Confirm the Welsh plug serial number and the tag coincide

 

[jimmbo]

Oh oh, we might have a FrankinMerc, or one where a previous owner stuck a 150 Cowl on to hide a 200, from casual inspection(some States get really goofy about Overpowering), or to have the fastest 150 on the lake, likely both

 

[BWR1953]

I will get compression numbers tomorrow and for sure get back to this forum, as for the fuel filter contents, I'm not even sure where it is. I know there's a little cylinder that fuel lines connect to beside the carbs but I'm not sure if that's where its located.

Make sure that you use a quality compression gauge. Cheap ones can give low numbers, sending you down a rabbit hole. BTDT.

 

[Dukedog]

0c267625 comes up as a 1990 200.. tha other number ya posted is a build date of feb 20 1984.. so tha power head has been changed.. got any pictures of tha power head?
below is a pic of a welsh plug jus in case ya don't know what ya lookin' for.. its on top of tha block behind tha flywheel.. it may or may not have a serial number stamped in it...

 

[karnage]

0c267625 comes up as a 1990 200.. tha other number ya posted is a build date of feb 20 1984.. so tha power head has been changed.. got any pictures of tha power head?
below is a pic of a welsh plug jus in case ya don't know what ya lookin' for.. its on top of tha block behind tha flywheel.. it may or may not have a serial number stamped in it...

Appreciate the help locating the welsh plug. Here's some pictures of the numbers and serial number, and a couple of the engine.

 

[Chris1956]

Check the fuel pump diaphragm. If they leak, a large amount of fuel just leaks into the water, and can foul the spark plugs.

After you check compression and spark plug color to make sure she runs on all 6, you may need to richen the carb idle mixture screws (if you have such) so she runs a bit richer at idle, to help with acceleration.

 

[QBhoy]

Were the carbs properly cleaned ? And properly set up ?
How’s the fuel delivery ? The vent on tank or remote tank ok ?
Other than all that…the complaint about the fuel consumption…I had a wee chuckle over that. Even when these things are running perfectly, they love a drink. I’ve a 150 on a 16ft boat. It’s just ridiculous for gulping fuel. It makes my v8 mpi boat almost like a Tesla in comparison. 50 litres she used for half a day out and likely only about 20-25 miles at most covered.

 

[Dukedog]

ya gotta add a "0" in front of tha number...

06519974.. 1984 150.. so its a 1984 2.0 150.. cowls are too..........
as said before tha 0C267625 comes up as a 1990 200... so clamp and mid are a lot newer..................

start with carbs and fuel pump rebuild.. no mater how clean everything might look it may not be so.. ALWAYS use new gaskets inside and out when ya take take either of these things apart.. replace all fuel hoses from tank ta carbs since that looks ta be a well used, "drop on", runnin' power head...... jmo.

 

[karnage]

Check the fuel pump diaphragm. If they leak, a large amount of fuel just leaks into the water, and can foul the spark plugs.

After you check compression and spark plug color to make sure she runs on all 6, you may need to richen the carb idle mixture screws (if you have such) so she runs a bit richer at idle, to help with acceleration.

I located the fuel pump this morning and removed it and inspected the cone shaped filter inside, it was very clean. For the diaphragm, are you referring to the fuel pump assembly where the fuel pump is? there is a fresh gasket on that and it is not leaking. I even put the ears on and let the engine idle for a minute and not a drop leaked from there, but I noticed something else. There are fresh rainbows in the water runoff, probably half of the puddle from the water is swirly rainbows. As for the carbs, I'm not positive where or if it it has an idle screw, there is a silver screw that is very hard to turn that I never touched. The big copper flathead one is an air bleed I believe, and idk about the flat copper one on top.

 

[karnage]

Were the carbs properly cleaned ? And properly set up ?
How’s the fuel delivery ? The vent on tank or remote tank ok ?
Other than all that…the complaint about the fuel consumption…I had a wee chuckle over that. Even when these things are running perfectly, they love a drink. I’ve a 150 on a 16ft boat. It’s just ridiculous for gulping fuel. It makes my v8 mpi boat almost like a Tesla in comparison. 50 litres she used for half a day out and likely only about 20-25 miles at most covered.

I sprayed carb cleaner and air through every hole I could and they were all clear. I put them on as I took them off and it runs well in idle out of gear, and it'll take gas as well. As for the gas, I guess you're right, I believe the engine will use some gas. But I believe something else is wrong. It went through probably 4 gallons yesterday and I idled maybe 3 miles total and revved it a few times. I noticed this morning while idling it with ears on that there is some big rainbows in my runoff puddle. I just checked the tanks air vent hose and it is a bit kinked, that's something for me to try to straighten up, but I believe it still functions.

 

[QBhoy]

I sprayed carb cleaner and air through every hole I could and they were all clear. I put them on as I took them off and it runs well in idle out of gear, and it'll take gas as well. As for the gas, I guess you're right, I believe the engine will use some gas. But I believe something else is wrong. It went through probably 4 gallons yesterday and I idled maybe 3 miles total and revved it a few times. I noticed this morning while idling it with ears on that there is some big rainbows in my runoff puddle.

Think the rainbows will just be 2 stroke.
I think you really need to clean the carbs properly, to be honest. Spraying them rarely does the full job. Been fooled in thinking it does, far too many times before now. Learned to just do them properly and save the wonder or bother of taking them off again.
Is the fuel definitely good and fresh ? Any filters fresh too ?
I’d also try pumping the fuel primer bulb to see if it makes a difference to things. That may indicate the rough health of the fuel pump occasionally.
When the oil injection was done away with..has it worked and performed since then ? If not, I’d look to see if you have any open ended oil fittings that are drawing air and not been dealt with accordingly.