Mercury inline 6 150hp rough idle

[Maxz695]

Re: Mercury inline 6 150hp rough idle

Looks like your on the right track. Good to hear the powerhead won,t have to be removed. I was wondering about that coil lead. Some leads are soldered and some are not like the replacement used set I got. I will be soldering them. Looks like those are soldered ends where the wire is connected

 

[sourbsted]

Re: Mercury inline 6 150hp rough idle

Well I had a good look at the motor. It's looking like the TDC is not right, silly me

If you look at the pic you can see a white dot on 6 degrees. It's looking like it could be TDC? I'm surprised the motor even run. Ill let yous all know how she goes in the water.. how many of you guys have told me this already.

 

[CharlieB]

Re: Mercury inline 6 150hp rough idle

I would not futz with the timing just as yet.

If you check the factory service manual you may find that little 'hole' at the one degree mark may be the .464 mark where the pointer should align when the #1 piston is at a measured .464 BTDC

The spots of white paint may be the how much the timing advances and first begins to open the carbs and the WOT timing.

When all else fails, read the directions in the FACTORY Service Manual before making any changes.

I think you are on the right track with cleaning the fuel system, a weak fuel supply is often the most common problem. After a simple spark test of each cyl proves adequate spark, it is generally a fuel problem.

 

[quicktach]

Re: Mercury inline 6 150hp rough idle

Can you post a copy of the link&sync you printed ? A PDF would be good. Thanks. You'll get the I6 going if you just persist. The tip about the CDI Troubleshooting guide is one to follow up on ...it's excellent. Sounds more like a fuel problem you've got. But you've got to check the electrics carefully too ...watch out for the advance working smoothly.

 

[sourbsted]

Re: Mercury inline 6 150hp rough idle

heres the link to the link&sync.. timing and sync of merc inlines. [Archive] - Sidewinder-Boats.com

Well i hit the water again, it still goes the same. I changed the idle mixture to 1 1/2 turns then it got even worse. So i set it at 1 1/4 and it improved. I kept trying to get it to plane and eventually it got up to a plane. And then it went very well, fast! Its just hopeless doing holeshot tests and stalls when you go to put it into gear..VIDEO0037.mp4 video by greenmk2 | Photobucket
I am going to take it out again and see if i can play around with the "primary pickup plate". I adjusted it so it had more of a gap so the dizzy would advance a bit more before the pickup plate would open the butterflys. I might go back to how it was and see how it goes..
In the photo below i had no gap at all between the tabs, so I adjusted the primary pickup so it had a gap of around a 1mm or 40 thou. I want to adjust the plate to how it was before.(close it up on idle position) Maybe that's it does go well doing the holeshot test..

 

[sourbsted]

Re: Mercury inline 6 150hp rough idle

Had anather shocker on the water today. She wouldn't plane at all. I tryed to adjust that primary pickup plate about 6 times, and it made no difference. Tryed mucking around with idle mixture screws, still no differance.

Has anybody else had crankcase seals fail??
Would the boat still plane?
I'm going to try to find a mechanic shortly, this is turning into a headache.. :/

 

[CharlieB]

Re: Mercury inline 6 150hp rough idle

Clams knows his stuff, follow his directions for the link and sync and timing to the LETTER.

Two stroke carbs do not have an accelerator pump to richen the mixture during acceleration, the idle mixture adjustment is absolutely CRITICAL to the smooth running of the motor.

After the link and sync and timing is perfected following Clams directions, clean carbs and rebuilt fuel pump, new fuel hoses and primer, adjust the idle mixture to 1 and 1/2 turns out from very lightly seated. This should give enough fuel to start and warm the motor.

Once warmed up shift into Forward gear, leave it at an idle then very S L O W L Y begin to adjust each idle mixture screw to 'Best Idle Speed'. Make very small changes, like just the width of the blade slot, and WAIT a minute or two between any change to give the motor time to burn off any excess fuel. This can take a while to get all idle screws perfectly set, so do NOT be in any hurry.

After perfecting this 'Best Idle ' while in Forward gear, the idle mixture must be adjusted even richer to provide the additional fuel for crisp acceleration. Here again, make small changes, just that blade width at a time, and TEST acceleration by trying a holeshot to get the boat on plane. ANY bog, hesitation, lean cough, indicates the need for more idle fuel. Make another small increase in idle mixture and retest acceleration.

Repeat to perfection.

Patience, and making those very small adjustments are key to perfecting the smooth running of your motor.

 

[sourbsted]

Re: Mercury inline 6 150hp rough idle

So Charlie your saying it could be simply as idle mixture? I tryed 1 1/2, 1 1/4, and even gambled 1 turn..
I thought I would tune it again before I head out to the boat ramp. And I did play around with the idle mixture too. I obviously messed It prior to going out again. I think I need an assistant out in the water, I keep having to anchor out. Bloody ski boats going up and down the river.. ggrr

If you look at the video it seemed like it was problem solved just some minor adjustments..
Thanks for everyones help.
Cheers

 

[CharlieB]

Re: Mercury inline 6 150hp rough idle

The idle mixture screw comes to a very small needle point, over tightening it squishes the soft aluminum seat, ditorting it, making the idle adjustment very very touchy, just the smallest part of a turn can make a big change in the fuel flow.

Making adjustments in very small changes and giving the motor a LOT of time to burn off any excess fuel that may be pooled in the main bearings, are critical to getting that perfect setting.

Loads of patience, you cannot hurry the motor.

But once done, there ain't NOTHING like the sound and feel of a Stacked 6 Merc!

 

[sourbsted]

Re: Mercury inline 6 150hp rough idle

Ok, yeah I made some adjustments of the mixtures screws a couple of days ago on the water. After that it seemed like It was almost going to plane, then after about 5 attempts it did (I got very excited!)
Then next morning I changed the mixtures and changed the primary pickup plates position, thinking I was doing a good thing WRONG! I messed it all up when I almost had it going good.
I'll follow your advice, and slow down, take my time..
Cheers..

 

[sourbsted]

Re: Mercury inline 6 150hp rough idle

Well I attempted the link& sync.
- I took out all the plugs except #1.
- hooked up timing light, cranked over the motor while the throttle stayed in it idle position.
Can't get it to change below ATDC 5 degrees, it just lights up on 464 mark if I turn the dizzy clockwise any more. Doesn't seem right.
When I start it and its idling it stays on ATDC 5 and if I lower the idle so it stumbles it goes back to 464 marker

I gave up trying to do the link&sync, I set the "primary throttle pickup" so It strikes the butterfly pickup as soon as I try to advance throttle. The primary pickup has run out of adjustment anyway. Cant turn it clockwise anymore.

 

[sourbsted]

Re: Mercury inline 6 150hp rough idle

Dow

 

[sourbsted]

Re: Mercury inline 6 150hp rough idle

I also found that the plugs were oil fouled. I think its because I couldn't get it to plane on my last water test.,Time before that I cleaned the plugs up and it planed then.

 

[sourbsted]

Re: Mercury inline 6 150hp rough idle

I hit the water again, made many fine adjustments to the idle mixtures. It did improve it but only a bit. I made some minor adjustments to the primary pickup plate, it made it plane, but still takes over 30 secs to get to plane. And against the current it won't at all. I chewed up 20 litres of fuel in one hour.. haha
I will try again another time.

 

[Maxz695]

Re: Mercury inline 6 150hp rough idle

Your crbs sound like the loading the engine big time. Stop messing around with all the timing crap and get the fuel situation in order. No way you should burn that much fuel just sayin. Something isn,t right with the carbs. If compression is good and theres fire on all cylinders thn the carbs are the obvious problem just my opinion

 

[sourbsted]

Re: Mercury inline 6 150hp rough idle

I had a look at the carbs, pumped the bulb and noticed fuel leaking out of the top filter cover. It doesn't seem to leak when motor is running.
The hull is taking on a lot of water, like probibly 40 ltrs after 4 hours. I've tryed fixing it but only improved it a bit. I'm putting in a bilge pump. Wouldn't help it planeing..

 

[Maxz695]

Re: Mercury inline 6 150hp rough idle

Did you use fiberglass and resin to fix the leak area? A bilge pump will work to remove most of the water. You should try to fix the leak though. Mostly a bilge pump is for removing wave splash that end up in the bilge and rain water. The automatic switch kicks on when the water level reaches a certain point and shuts down when the level drops the switch shutting it off. I know any water in the boat will affect the planing abilities. When I was running my 40 HP and filled the fishwell in my bass boat (About 6 to 8 gallons) there was a tremendous different in speed although it did get up on plane. I never used it after noticing that. I finally got a bigger engine to handle that now.

 

[sourbsted]

Re: Mercury inline 6 150hp rough idle

It was taking water through the motor mounting holes, I used some silicon to seal it. The two other sealed areas inside the boat under the floor are taking on water now. Going to have to have a good look again.
When I first started tuning the motor on the water,and I had the motors covers off, I could manage to get it to plane after 30 sec of so. The motor was screaming, I was getting the thumbs up from people watching, however Once I tryed to put the motors covers back I would had no chance of getting it to plane. Weird?? I am thinking the motors insulation is coming loose and causing a restriction. Also the amount of water in the hull could be fall back.

 

[Maxz695]

Re: Mercury inline 6 150hp rough idle

Yea I love opening it up with the cowel removed people look and say what the hell does he got on that thing. I know it may be a pain in the butt to remove the engine and repair the mount holes by lightly sanding the surface to get the silicone to adhear to it better but it would be the best thing in making the repair last.

 

[CharlieB]

Re: Mercury inline 6 150hp rough idle

........................... I had the motors covers off, I could manage to get it to plane after 30 sec of so. The motor was screaming, I was getting the thumbs up from people watching, however Once I tryed to put the motors covers back I would had no chance of getting it to plane. Weird??...........................

You need a helper, run the motor on the hose with the covers OFF

Spray the exhaust side cover gaskets area and the lower exhaust plate, where the motor bolts down to the mid-section, spray with a very soapy mixture, have your helper hold a plate of something against the prop while you hold something against the exhaust vents at the top of the mid-section. You want to slightly pressurize the exhaust and mid-section while watching the soaped exhaust gasket areas looking for 'bubbles' indicating exhaust leaking inside the engine covers, displacing oxygen and causing the motor to loose power with the covers on.

IF you find soapy bubbles, you will need to take those sections apart, check to be sure the surfaces are flat, clean, and install new gaskets, tightening all bolts evenly and only to the torque values specified in the factory service manual.