Merc 150 V-6 idle problems

[outboard tech]

Re: Merc 150 V-6 idle problems

Possibly not a carb problem,dude, but that's what happens when you're guessing. Any good tech could diagnose your problem in minutes on the lake with the right tools. Notice a sync and link is performed on the water, in gear, with a timing light. But if you still have a lean spit, you have either a fuel/carb problem, a broken bleed hose,a broken/chipped reed, or the timing to fuel ratio is incorrect. Also they were somewhat correct about exhaust backpressure affecting idle; but you need to trim DOWN to achieve a richer idle. Next time you throttle off, try momentarily bumping your key in when she's about to die,if that keeps her running, you have narrowed it down to the #2, or 3 carb, #1 does not prime. You also need to confirm your thermostats are working, cold v6 mercurys won't idle well.

 

[dicktaber]

Re: Merc 150 V-6 idle problems

Thanks again, Ben. I will go back and check the timing again, but the throttle cam has the prescribed 1/4" space. Only thing I was having a hard time with was the 11/16" measurement on the timing advance linkage--couldn't quite understand what/where they were measuring. I have a Merc manual, a SELOC, AND a Clymers, and none of them has a satisfactory explanation of this. Also, can't find a thing on the bleed system, it's function, or how to test it. Are they check valves with moving parts or just calibrated orifices? What is their purpose? Can I "blank them off" for testing purposes? <br />As far as the "good tech" theory goes, my local Merc shop didn't want to take it to the lake, they wanted to rebuild carbs first, then start changing electrical parts. Shotgun troubleshooting with my wallet as the immediate casualty...<br />Everyone on the board has advised Seafoam first, carb disasembly/rebuild second. I have followed all the advice given and am grateful to all that have replied.

 

[outboard tech]

Re: Merc 150 V-6 idle problems

OK a lttle more info and I gotta go. Sorry your local techs blow. Sad thing in our industry. Forget the 11/16 measurement, that's the trigger link and it can't move unless you changed it.You lost me on the 1/4 space cam. Just position the roller so it does not make contact. There are 3 adjustments on the spark arm and I fear you have them out of adjustment. Remove the cable,the lower adjustment is idle stop--set the cam there.The next one up is idle timing, that adjusts while running in gear. the top adjustment is max. timing stop; and you DO NOT want to fool with that without a timing light. The bleed system moves unburnt fuel from the cyls. back to the intake (reed box) to feed combustion, and you only have to inspect that none have broken or fallen off--but the starboard side requires removal off the electrical bracket. The check valves for the bleed are on the reedbox--but they rarely fail--to test -you should be able to suck on the hose but not blow through it, but that's probably not necessary. You can hear a broken bleed hissing while the motor idles, and the system does not affect high throttle operation.

 

[dicktaber]

Re: Merc 150 V-6 idle problems

Ben--<br />Thanks for all the info and help. The 1/4" is what the Merc manual says you should have between the cam roller and the actuating arm at idle. I have not touched the trigger link. The idle timing sounds most likely, but I followed the Merc book and it did not seem to address this (except the dial indicator, TDC, and timing mark bit). When I had the carbs off I stuck a flashlight down each intake. No broken reeds, and none that did not seat. I stuck a finger GENTLY down each to make sure no reeds were stuck closed, and moved each reed about 1/16". I will inspect the bleed hoses and fittings--I know what you mean about only being able to see 1/2 of them. Now that I know where-and-which-direction the check valves operate, I will check those, and the hoses as well. I'll post back, and thanks again.

 

[dicktaber]

Re: Merc 150 V-6 idle problems

Okay, I checked the routing of all the bleed lines with the Merc manual. Each is routed and connected correctly. I blew into each, and sucked several partial mouthfuls of gas--the check valves seem to be working correctly (I can suck air (and premix) from the cylinders towards the airbox but cannot blow back towards cylinders). No bleed hoses leak. No broken bleed fittings. Once again, compression is 130 on three cylinders, 133 on one, 135 on one, 140 on one. Seafoam is done (both kinds) and carbs have been completely disassembled, dipped, and rebuilt. Stator checks done in accordance with Merc manual. Fuel is fresh, and motor runs great above 1200 rpm. What am I missing?

 

[jetfiremuck]

Re: Merc 150 V-6 idle problems

Remove airbox cover get a can of carb cleaner. Spray into each carb one at a time. If the engine smmothes out at idle youve isolated the problem. You need to switch carbs to that cyl to Verify carb, cyl or ign circuit. Stick with the basics with diagnosis you can overlook something. Hope this helps.

 

[dicktaber]

Re: Merc 150 V-6 idle problems

jetfire--<br />I know that there have been an awful lot of replies and back-and-forth going on here, and it's hard to follow what has been done. The carbs have just been thoroughly disassembled, new gaskets/rebuild kits, etc. I have been advised not to use carb-cleaner-in-a-can, as it may damage soft parts, and with all those nice new shiny parts in there I'm reluctant to go against that advice. Secondly, the motor will usually idle just fine. It will start hard, and may die a few times when cold--it will chuff and die occasionally, but will start back up. So spraying something in at idle tells me very little. My problem (engine dies) generally occurs either:<br />--just as I start to advance the lever, whether slowly or quickly, or<br />--as I reduce power back to idle (always done is a slow, deliberate fashion as the boat sits low and will fill the splashwell if I "chop" power).<br />Please note that it will not die "every time" and the problem is not necessarily easy to induce. It will seldom do anything unusual on the muffs (hard starting excepted). In the water, if I operated it for an hour or so, it will happen sooner or later--maybe each time I pull back the power to traverse a no wake zone, maybe after I've idled through it and attempt to accelerate.

 

[LubeDude]

Re: Merc 150 V-6 idle problems

I have followed this thread with GREAT intrest, as I have a merc 150 with the same basic situaltion, I too have done all that you have to no avail. I am going to change the reeds this next winter or early spring, I have about decided that they are week. Mine is a 1987 model.<br /><br />I have fished with it all summer this way, as it runs like a scalded cat at WOT and anywhere in between except like yours, it will die out if I chop it off, or ease into the trhotle. It does seem to change RPMs a little if Im criusing along at say 4,000 RPMs just slightly,(not a real miss) just not REALLY smooth.

 

[dicktaber]

Re: Merc 150 V-6 idle problems

Thanks Lube Dude, and no matter what I find I will post the result. Looking back I see that I've now owned this boat for just over a year. Bought it at the end of the season last year living in IL, had it out twice. This season between moving to Dallas and work-and-all, I've only had it out three times, about an hour each time. Sure is frustrating to take a year to (not) figure out a problem.

 

[LubeDude]

Re: Merc 150 V-6 idle problems

Sounds like we bought our boats about the same time. I looked all summer before deciding on this on, or even finding one I want for that matter. I really thought the problem was just bad gas or maybe dirty carbs, but to my surprise, Its none of the above. Im hoping that the reeds fix the problem. Now Im having trouble deciding what reeds I want to use?<br /><br />

<br /><br />As you can see, it runs great at WOT

 

[jetfiremuck]

Re: Merc 150 V-6 idle problems

My suggestion of spraying carb cleaner in to the carbs while the engine is at idle in the water is to enrichen that cyl to see if its a fuel related problem then verify that with a carb switch to ensure its the carb or cyl issue. ifthat checks out ok use a test lite to ground each cyl thru the spark plug boot at idle you may have a weak coil or power pack. Im assuming that youve run a seperate fuel tank with known good fuel.Remember idle speed and mixture must be done with the engine in the water. The carbs if removed must be put back matched by id #to the correct cyl location per shop manual

 

[ronmold]

Re: Merc 150 V-6 idle problems

I've had several issues much like yours w/my '86 175 that I thought was fuel related but because of 1 switchbox failure I replaced them both with CDI units. ALL the other problems went away - hard starting, dying at idle, roughness at 1800-2500 RPM. If your switchboxes are old I recommend replacing them and the stator w/ CDI stuff. Also still runnin' 80:1 Amsoil Saber with over 150 gal of gas this summer and havn't seized'r up yet!

 

[MMTech1]

Re: Merc 150 V-6 idle problems

Ok sound like you have checked the carbs, and the recirculation lines are ok along with the check valves. Don’t forget the reeds. Now forget about the ohms on the stator. Ohms reading can change with temp. To check the stator you need to check it with a DVA meter or replace it with a known good one, before saying your stator is ok. Weak out put from the low speed side will cause your problem. Most manuals back then only had tests for stators in ohms, and were found unreliable. You can ask your local tech for the specs on the stator, he/she should have them. The high side of the stator will kick in about 1800rpm that is why motor runs great on high side. The low speed side is from 400 to 1800. Good luck.

 

[dicktaber]

Re: Merc 150 V-6 idle problems

Once again, thanks to all for the help.<br /><br />Jetfire--adding fuel (whether with enrichener or whatever) does not help. When it dies, it doesn't miss-sputter-die, it goes "chuff" and stops like you turned off the ignition switch. All carbs are in the the correct position. Idle speed seems to be dictated by the closed throttle plates and air and fuel allowed through the passages with the plates closed. There is no obvious idle mixture adjustment on these carbs, nor do any of my three manuals show an adjustment for idle mixture. I am guessing this is accomplished by changing idle jets and vent jets. <br /><br />Dasboot/MMTech1--I am leaning more towards ignition as I've been as far down the carb road as I can go. Reeds--when I had the carbs off I stuck a flashlight in each intake port and verified no broken/missing reeds; also reached a finger in and verified a) that each is seating and b) that each moves easily. <br />Prior posts have stated that the stator either works or it doesn't--if the low side goes away it will not start at all; if the high side goes it will not run above (insert favorite rpm here). If this is not true (and the last two posts seem to indicate this) then there may be hope yet. You are correct inasmuch as the only readings I have were in ohms (from the Merc manual), and in a previous post I stated that the readings were all in-or-very-close-to specs, which I attributed to the fact that I was taking the readings outdoors in Illinois last winter...definitely an opportunity for a temp-induced variance. Is there another way to check? Also, more info on CDI please? Is this a brand name, where available, how much? I've read about "red stators" and have the Seiler Marine website available but they do not seem to sell switchboxes. I've been avoiding "throwing" electrical parts at the motor but I may be at that point.

 

[LubeDude]

Re: Merc 150 V-6 idle problems

Originally posted by Knot2much:<br /> I've been avoiding "throwing" electrical parts at the motor but I may be at that point.

I had all my electrical checked at the local merc dealer, and they found nothing, I even had them go out with me for about an hour for "FREE" Wow, that dosent happen very often. They tried everything, every test, checked everything, he set back by the engine, held hand over carbs one at a time, looked felt and tested pumped bulb, everything he could think of, nothing, he thinks it must just be week reeds. He says they will look fine, (which mine do), but if they are week they will flutter at low RPMs.<br /><br />I doubt if throwing money at your problem will solve anything, But who knows, you may not have the same problem as mine, just the same symtoms.

 

[dicktaber]

Re: Merc 150 V-6 idle problems

Thanks, I'll ask my Merc Service guy about weak reeds but this sounds a little fishy to me. I've been messing with two-strokes since the very early 70's--mostly motorcycles and snowmobiles, which generally run more hours at various throttle settings--and have never heard of weak reeds. Changing reeds because they were broken, yes. Changing to Boyesen or V-Force for more power, yes. Maybe if I heard of someone that had this (or any) problem and fixed it by changing the reeds, I might be more convinced, but I've spent some time reading the posts on this board and this is the first time I've seen that one. Anyone else care to weigh in?

 

[ronmold]

Re: Merc 150 V-6 idle problems

CDI/Rapair makes aftermarket outboard parts that improve on the weaknesses of factory stuff - less $$$ too! Look here for stator & switchboxes<br /> http://www.seilermarine.com/rapair/mercury.htm

 

[Clams Canino]

Re: Merc 150 V-6 idle problems

Originally posted by Knot2much:<br /> Anyone else care to weigh in?

Reeds at speed are the puppets of inertia and the flow, they just flap thier little hearts out. At idle they somewhat require thier own elasticity to spring them closed at the right time.<br /><br />I can **kinda** buy into a reed theory... and I bet you can change them out cheaper than electrics.<br /><br />-W

 

[LubeDude]

Re: Merc 150 V-6 idle problems

Originally posted by Clams Canino:<br />

Originally posted by Knot2much:<br /> Anyone else care to weigh in?

I can **kinda** buy into a reed theory... <br />-W

Thanks Clams.<br /><br />I would like to run something by you, I bought an intire intake tystem off Ebay a few weeks ago, I got a great deal on it, and just felt it would be good for a lot of parts, plus it lets me play with it an still fish the rest of the season. Im in the process of rebuilding the whole thing, and then this winter or early spring, I will just change it all over in one day.<br /><br />Well, I was quite surprised when I took the reeds out and looked at them closely, they are 1985s.If I held them up to the light. I could see more light than I thought was right. after taking them apart, I was again surprised that the cages were never Lapped flat, just cast, and the reeds had over the years worn into the aluminum cages a little, also, the reeds themselves were worn on the edges very slightly, pretty shiney.<br /><br />I took a peice of 1/4" flat glass and 400 grit wet paper, and with WD-40, lapped them, followed up with 1,000 grit. Now, I am going to put "new" reeds in before I put this assy on the engine, but just for kicks I assembled them again and held them up to the light, guess what, I couldnt see light at all.<br /><br />So, weak, worn reeds, worn cages, whatever, I think that it still probably is a reed problem.<br /><br />Just sharing.

 

[dicktaber]

Re: Merc 150 V-6 idle problems

LubeDude--<br />Great input--please let me know how it works. I checked for Boyesen reeds, and for a mid-80's 150 XR they don't show a listing...but for later V-6's, the reeds are $172 per set. Not ready to semi-major disassembly to change $200 worth of reeds on a "maybe"... <br />Hey, if you install your remanufactured setup on your motor and it works, maybe you want to sell the removed unit to me, and I can go through the disassembly/cleaning/lapping/reassembly process...