86? 150 Blackmax fireing #1 on wrong stroke

[3899]

Hello, I store a bass boat every year for a friend, and do some work for him when needed. He has this 150 hp ser # A905691. He says that it starts good, idles good, but boggs on take off, and won't get on plane at all. He's had it to the merc shop near his home twice last summer, and still no help. He didn't keep any paperwork, so not sure what all has been done. I can see heads have been resealed. I'm going to replace the fuel hoses (rock hard) but in the meantime, I started to check the ignition. It looks like the stater and or the trigger is newer, so I thought I would check the trigger timing. Marked all 6 cyl's at TDC. I'm assuming that the #1 cyl is the left lower cyl as your looking at the plugs. That is the cyl that is at 0 on the timing mark on compression. All the cylinders check good with the timing light, except #1 (lower left cyl) it is actually fireing on the second stroke. The 0 timing mark is over by the starter when it triggers. Would it be possible that the trigger is bad? Does seem to have good spark on all cylinders (with timing light cranking-havn't ran motor yet.) This motor was always a great performer for him. I've always been amazed at how quick it came out of the hole and on plane. He's always had a merc marina do his work, and winterize. Any thoughts?
Thanks!
Jeff

 

[Maxz695]

Re: 86? 150 Blackmax fireing #1 on wrong stroke

By no means an expert on this engine not even a novice so many grains of salt with this. I have heard of mis markings of the color code on triggers from the manufacturer. Someone may read this and clerify this for you. Just some info that might be of some help to you

 

[3899]

Re: 86? 150 Blackmax fireing #1 on wrong stroke

Just to add to this, if the the trigger was wired wrong, wouldn't I have trouble on two cylinders? I have read where other people had trouble with this, but seems like it was always two cylinders off.

 

[CharlieB]

Re: 86? 150 Blackmax fireing #1 on wrong stroke

Switch the two switchboxes then retest to see if the problem has moved to the other side of the motor, if so, replace the switchbox.

Because there is NO RETURN on electrical parts you want to PROVE the part bad, do NOT assume it.

 

[out 2 launch]

Re: 86? 150 Blackmax fireing #1 on wrong stroke

I'm assuming that the #1 cyl is the left lower cyl as your looking at the plugs. That is the cyl that is at 0 on the timing mark on compression. All the cylinders check good with the timing light, except #1 (lower left cyl) it is actually fireing on the second stroke. The 0 timing mark is over by the starter when it triggers.

Unless I'm misreading you the #1 cylinder, as viewed from the back of the motor looking forward, is the top one on the right.

 

[Barnacle_Bill]

Re: 86? 150 Blackmax fireing #1 on wrong stroke

#1 is top starboard. This is a perfect example why it is important to learn port and starboard.

 

[3899]

Re: 86? 150 Blackmax fireing #1 on wrong stroke

Interesting....that one doesn't line up with 0 on the flywheel either then. I guess it doesn't realy matter how I numbered them, they trigger the timing light at each correct TDC compression stroke that I aligned to the timing pointer. The only one that did not trigger at it's corresponding trigger mark was the port bottom cylinder. I will look closer tomorrow night.

 

[out 2 launch]

Re: 86? 150 Blackmax fireing #1 on wrong stroke

So true bhile, but sometimes when people use references in left and right it only confuses them more by switching to less confusing terms.
What is even more confusing his how the "assumed" #1 cyl on the lower left @ TDC lines up with the 0 Deg mark at the pointer. And then there is talk of mis-marked triggers and switching switch boxes. Im already confused. LOL.

 

[Faztbullet]

Re: 86? 150 Blackmax fireing #1 on wrong stroke

Sounds like flywheel was taken apart to change stator and reassembled wrong...this means timing was not checked when repair was complete :grumpy:

 

[out 2 launch]

Re: 86? 150 Blackmax fireing #1 on wrong stroke

Kind of hard to miss align the fly wheel with the crankshaft key installed, but I guess anything is possible.

 

[Faztbullet]

Re: 86? 150 Blackmax fireing #1 on wrong stroke

Kind of hard to miss align the fly wheel with the crankshaft key installed, but I guess anything is possible.

If you remove bolts that hold it to center hub you can reinstall it where no timing mark line up....

 

[Capt Ken]

Re: 86? 150 Blackmax fireing #1 on wrong stroke

Actually the bolts are offset just a bit so keep that from happening. If it was in the wrong bolt holes, none of the cylinders would fire. If it idles fine in gear, then all the cylinders are firing like they are suppose to. Bogging it either timing not advancing or carb's dirty and if someone can't figure out which cylinder is #1, then I wouldn't advise them to go into the carbs.

 

[Maxz695]

Re: 86? 150 Blackmax fireing #1 on wrong stroke

I agree there. The first thing I would do is start from scratch. Find out which cylinder is #1 and it,s usually maked somewhere. Possibly a manual will identify which one it is. After that set #1 @ TDC then check the line up makings on the flywheel to see if it is set to TDC. If not take the flywheel lose from the hub and reset it to it,s proper position. Re Check the timing at that point.

 

[out 2 launch]

Re: 86? 150 Blackmax fireing #1 on wrong stroke

First rule of thumb,
The top cylinder is number one.

For those a little confused, when looking at a V block, notice the spark plug locations on the starboard (right) bank are staggered above those on the port (left) bank. Starting at the top: Starboard #1, port #2, starboard #3, port #4 etc. In different terms, descending from the top, the starboard bank is numbered 1 3 5 and the port bank is numbered 2 4 6.

 

[Chris1956]

Re: 86? 150 Blackmax fireing #1 on wrong stroke

Gee, You should listen to Fazt. He is an expert. There are a lot of guesses on this thread. Also, two-cycle motors fire on every stroke.

 

[out 2 launch]

Re: 86? 150 Blackmax fireing #1 on wrong stroke

There are a lot of guesses on this thread. Also, two-cycle motors fire on every stroke.

I think the better terminology would be two-stroke because the complete Otto Cycle (intake, compression, ignition, power, and exhaust) are completed in two strokes. A stroke being 180 Deg of crankshaft rotation TDC-BDC. Therefore a two-stroke engine fires (or produces power) every two strokes or 360 Deg of crankshaft rotation not on every stroke. This of course is referring to each cylinder, multiple cylinders provide power stroke overlap over the 360 Deg of rotation. That's my guess.

 

[CharlieB]

Re: 86? 150 Blackmax fireing #1 on wrong stroke

If the OP turned the motor and marked each individual cyl at TDC at a designated clock position on the flywheel, then checking timing on each cyl SHOULD show each cyl's mark in the same position. Period.

The fact that only ONE cyl's mark appeared in a different position lends weight to his theory that the timing on that particular cyl is incorrect.

If a trigger were out of phase it would have an effect on two cyl's, such is the reasoning in switching the switchboxes, if the incorrect timing then changes sides, following the switchbox, that pretty much indicates there is a problem with that switchbox. This is a cheap test costing only the OP's time and saves cost of purchasing any NON-returnable electrical parts.

A two piece flywheel may or may not be bolted together making the timing marks clock incorrect to the hub keyway, however this will NOT affect ignition timing, the trigger magnets are in the hub section and unchanged from the misalignment. Timing marks will be clocked wrong and the user may 'think' something is wrong, and start making changes before realizing the assembly error. We ALL make a mistake sooner or later, hopefully we have learned something from it. Check EVERYTHING before spending anything on electrical parts.

 

[3899]

Re: 86? 150 Blackmax fireing #1 on wrong stroke

CharlieB, out2lunch, thank you for the responses I needed. Tonight I rechecked everything. I knew that #1 was either the PORT lowest cyl or the STARBOARD upper cyl. I couldn't find the cylinder numbers-they had been crudely painted over (probley after heads were reinstalled). I had to scratch a heavy layer off to see the markings. So that's why I asked in my posting...just to make sure. What I finally figured out, was that 0 TDC on the flywheel was not matching up with ANY compression strokes. I marked it without actually matching it with any compression stroke (assuming). That is where I made my first mistake. In fact when the timing pointer is at 0 TDC on the flywheel, #1 cylinder is on BDC. So I remarked and rechecked all the cyl's, and my triggers are all present and accounted for on each comp stroke. I would never have guessed that the flywheel could have been installed incorrect. Just thought it would be keyed and installed one way. So I ask, at this point, is there some adjustment that should have been done (but could not because of the incorrect installation) that could possibly help me with some of my symptoms? OR, should I just leave the flywheel where it is, note on it that it is wrong, and go onto other issues? I will be addressing the fuel issues as I go along...I can figure this stuff out, as long as no one minds a few dumb questions along the way. I admit, I am a relitive newbe to two stroke repair (Mercs for sure). Thanks again!
Jeff

 

[Faztbullet]

Re: 86? 150 Blackmax fireing #1 on wrong stroke

So I ask, at this point, is there some adjustment that should have been done (but could not because of the incorrect installation) that could possibly help me with some of my symptoms? OR, should I just leave the flywheel where it is, note on it that it is wrong, and go onto other issues?

Get a dial indicator, find #1 TDC,remove bolts from flywheel as they are not offset and set at 0? or as close to mark as you can get, set timing pointer to .462 and adjust pointer and your good to go testing. Reindex flywheel to be certain you are at TDC on all cylinders. If timing is low on that cylinder still,swap switchbox as suggested. If problem follows box, ohm the bias circuit of both boxes as they way these tie together the box with cylinder acting up may be good and other is bad even if it works fine, this is why they are recommended to be replaced as a pair by factory and CDI....

 

[Dukedog]

Re: 86? 150 Blackmax fireing #1 on wrong stroke

Fb, pm your number please. Lost all my stuff on this fancy phone. Or call me 817-929-1129