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Max Online: 36273 @ 01/23/13 02:34 PM
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#12353452 - 07/22/17 04:41 PM Merc 150 Black Max question
bronco71 Online   content
Extreme Angler

Registered: 02/05/06
Posts: 1318
Loc: Farmers Branch/Sulphur Bluff
My old 2.0 liter Merc 150 has been running like [censored] lately, rebuilt carbs, changed filters, new plugs, new voltage regulator and stator last year and ran great then. Now holeshot is terrible even with a 19p prop, I normally run a 22p, and when I finally get on plane it doesn't want to go over 5000-5300 rpm wot. With that prop I normally have to back off throttle to not go over 6000.
So I feared I had lost a cylinder and finally got brave and did a compression check, when pulling plugs 1 and 2 looked way too clean. All cylinders showed 80psi which I will accept for a 37 year old motor....so no bad cylinders!
Put plugs in and fired it up on the hose, pulling #1 plug wire off got no difference in rpms, same with #2. Nearly died when any others were pulled.
So, am I looking at a bad coil or will a power pack do this? Coils are original and power packs were changed once years ago.....

UPDATE: freak rainstorm is over and I got to work on it some more. When removing coils 1 and 2 I realized that #1 plug wire was almost 3/4" out of the coil, I'm thinking I may have had an intermittent spark here. I realized also that these 2 cylinders are on 2 different power packs so I decided to replace both coils at this point. Should arrive tomorrow and I will install and hope for the best.


Edited by bronco71 (07/22/17 08:18 PM)

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#12353715 - 07/22/17 08:17 PM Re: Merc 150 Black Max question [Re: bronco71]
gary purdy Offline
TFF Guru

Registered: 05/24/03
Posts: 11129
Loc: Littlefield Tx & Lake A. H. US...
First see if your getting spark to #1 and #2 cylinder. If not you have an ignition problem. If you have spark you have a carburation problem. Can you post a picture of the lean sparkplugs?
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#12353728 - 07/22/17 08:22 PM Re: Merc 150 Black Max question [Re: bronco71]
bronco71 Online   content
Extreme Angler

Registered: 02/05/06
Posts: 1318
Loc: Farmers Branch/Sulphur Bluff
Thanks Gary, just updated original post as you were posting. #2 was getting no spark and #1 wasn't getting spark when I tested it but I noticed that the wire was pulled 3/4" out of the coil as I removed the coil. I have 2 coils coming tomorrow....

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#12354032 - 07/23/17 05:28 AM Re: Merc 150 Black Max question [Re: bronco71]
TLW Online   content
Extreme Angler

Registered: 11/16/06
Posts: 2206
Loc: ft worth
plugs clean and dry is really lean and/or no fuel.. plugs wet/oily really dark, fat and/or no fire.. in your case with first generation motor ('76 to '82) really clean and no fire can also indicate a leaky divider plate (water).. common problem with first gen. with age....

you can swap switch box leads at coil 1 with 3 ta see if problem follows and same with 2 and 4.... coils rarely go bad, especially two at a time....

no fire on opposite bank cylinders is "usually" stator.. not always though.. sometimes trigger.. if 80 lbs is a true reading motor is tired and needs attention if ya gonna depend on it...



Edited by TLW (07/23/17 05:37 AM)

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#12354037 - 07/23/17 05:52 AM Re: Merc 150 Black Max question [Re: bronco71]
tmd11111 Online   content
Outdoorsman

Registered: 04/30/17
Posts: 231
Loc: San Angelo
Provided you did a compression test with the motor warm and the throttle held open then 80psi is a bad thing. It takes almost that much just to ignite the fuel.

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#12354253 - 07/23/17 10:22 AM Re: Merc 150 Black Max question [Re: bronco71]
bronco71 Online   content
Extreme Angler

Registered: 02/05/06
Posts: 1318
Loc: Farmers Branch/Sulphur Bluff
Thanks guys, I work on a lot of trucks but don't do much but the basic maintenance on outboards, this one hasn't needed much. Looks like I did the compression check wrong, engine was cold and throttle closed, but I hope the even readings mean something. It starts pretty easy without a lot of cranking, usually only needs to turn over a fraction of a second when warm to start, not like low compression needing to turn over a lot to get it to start.
Since 2 coils will be here today I will put them on and see if I get spark, if that doesn't fix it I will continue checking according to your recommendations.
I'm sure it is getting tired and I imagine the reeds are in bad shape but if it will fire on all 6 with the new coils hopefully it will last a while longer. I don't take it on long trips or tournament fish so when it finally goes it won't be ruining a major trip, it will just be a long trek back to the ramp with the trolling motor....

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#12354273 - 07/23/17 10:42 AM Re: Merc 150 Black Max question [Re: bronco71]
TLW Online   content
Extreme Angler

Registered: 11/16/06
Posts: 2206
Loc: ft worth
would be good ta check with different gauge also.. they are known ta vary..especially if it (gauge) hasn't been in your possession since birth!.. if 80 lbs is true no mater warm, cold, open or closed its low as long as ya did it with all plugs removed.. if ya do run it monitor tha comp ona regular basis..... gl with it.

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#12354283 - 07/23/17 10:53 AM Re: Merc 150 Black Max question [Re: bronco71]
bronco71 Online   content
Extreme Angler

Registered: 02/05/06
Posts: 1318
Loc: Farmers Branch/Sulphur Bluff
Thanks! gauge is brand new, didn't trust my old one! All plugs were out, I figured 90 - 110 would be more in range. I actually expected worse than 80 and over 10% difference between cylinders. When I said 80 on all they were actually 79 - 82, just didn't want to post complete readings since they were all close.

Will keep an eye on compression, when it is toast I will probably upgrade to a 175 since the hull is rated for 185....Thanks again!

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#12354332 - 07/23/17 11:34 AM Re: Merc 150 Black Max question [Re: bronco71]
jbobo Online   content
Extreme Angler

Registered: 02/26/13
Posts: 2381
Loc: springtown,tx.
On older 2 strokes 80 psi isn't bad. Not great but definitely has a lot of life left. Newer motors need higher compression for some reason. When you have more than 10 lbs of difference between cylinders is when it's bad. Then is time to rebore and oversized rings.
Agree with above that coils seldom go bad and almost never 2 at once. Power pack is my guess. I have been wrong before though.
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#12354338 - 07/23/17 11:37 AM Re: Merc 150 Black Max question [Re: bronco71]
TLW Online   content
Extreme Angler

Registered: 11/16/06
Posts: 2206
Loc: ft worth
under 110 they are startin' ta wear and rings will lose tension which is actually worse.. more so than ring face (chrome) wearin out.... jus keep a good eye on it.. it will let ya know but ya may not like it...

tha "no fire" with "clean plugs" is what needs ta be fixed before ya run it anymore anyway..... take a flashlight and see if ya can see tha piston tops in those two holes.... compare what ya see to tha other holes.


Edited by TLW (07/23/17 11:44 AM)

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#12354591 - 07/23/17 03:31 PM Re: Merc 150 Black Max question [Re: bronco71]
bronco71 Online   content
Extreme Angler

Registered: 02/05/06
Posts: 1318
Loc: Farmers Branch/Sulphur Bluff
update: 2 new coils, good spark to all 6 cylinders. Sounds better and smoother, doesn't load up and die idling...at least not on the hose...starts up easy with barely a click of the key.
busy week coming up, not sure when I will get to lake test. Will check plugs and piston tops after lake test....


Edited by bronco71 (07/23/17 03:33 PM)

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#12354644 - 07/23/17 04:10 PM Re: Merc 150 Black Max question [Re: bronco71]
TLW Online   content
Extreme Angler

Registered: 11/16/06
Posts: 2206
Loc: ft worth
good for you.. jus take care of it now!.. goes ta show how good at diagnostics ona keyboard can be, huh!..... hammer

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#12354651 - 07/23/17 04:14 PM Re: Merc 150 Black Max question [Re: TLW]
bronco71 Online   content
Extreme Angler

Registered: 02/05/06
Posts: 1318
Loc: Farmers Branch/Sulphur Bluff
Originally Posted By: TLW
good for you.. jus take care of it now!.. goes ta show how good at diagnostics ona keyboard can be, huh!..... hammer


I've received a lot of good info on here and even if it doesn't apply now it is stored away for the future! Thanks again to all, hopefully it will run better next time on the lake!


Edited by bronco71 (07/23/17 04:15 PM)

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