Trigger Control Arm Linkage Adjustment

[Qshot1989]

On a related note, who has recorded data on the difference between WOT and true WOT under load in a test tank or at ramp? I am curious how accurate it is checking when it is not in the water. Thanks!

[25two.stroke]

On a merc v6 or I6 I've seen it retard 2-3 degrees from cranking WOT...but this is not with a test wheel. We always run them with just their regular runnin prop so real WOT rpm is not achieved. On a 6000 rpm motor we normally see 4500 rpms at WOT at the ramp...this is when we see like 20 degrees on a motor set at 23 deg WOT at cranking.

I think the older OMC books note this drop and some of the consumer mercs say on their timing sticker:
Idle 0-4 ATDC
WOT 21 BTDC
WOT (cranking) 23 BTDC
Which notes that you will see a decrease

[kbahus]

Thanks for the continued information. I fully removed the idle stabilizer and got it fired up on the hose today. Idle timing is about 8-10*aftd and it seems happy. I tried to get it closer to zero and it was not happy. Also, it started running erratically like it did last season. I thought for sure the trigger would take care of it as all of the potting was cracked and I had a misfire on 1 and 4. Anyways, it purred like a kitten last week, but now it's just not right. When it started running erratically I noticed today the tachometer was bouncing all over the place. When trying to rev it up on the hose it would die if I let off the throttle rapidly with the hotfoot. I did hook up a DDT and verified TPS voltage of .22 and idle speed of 650-675rpm. I am trying hard to reach back to my days of marine work and I feel that a bad tachometer can cause running problems, is this correct? Also, I feel like the key switch could come into play here too?

Also, I have not tried to check wot timing with the bias wire connected and disconnected, perhaps I should.

[25two.stroke]

Nah you have some other problem right now, I wouldn't worry about the WOT timing yet. Your tach bouncing indicates that your issue is linked to the charging system some how. Tach can cause problems, do you have another control box you could hook to it? You don't have to mount it, just plug it in at the motor. If you don't you can start by disconnecting the grey wire at the motor where it comes out of the 9 pin pigtail. It does sound most like a bad tach. I don't understand theoretically how the tach or the rectifier can make a motor run poorly cause they are different sets of windings on the stator, but many people on here have found that it can lead to troubles like you are having.

Also, have you done the bias circuit tests? I assume you've verified the stator output is good. Bias circuit won't affect tach, but it could definitely make your motor run bad. Just a few simple tests and you can rule it out.

[Qshot1989]

What are everyone's thoughts about making sure spark plugs are thoroughly grounded on a spark board before attempting WOT(cranking speed) tests? I hear mixed opinions about additional voltage stress on switch boxes if plugs are not grounded well.

[FORBESAUTO]

Can you explain why? Ive done it both ways and testing cranking speed timing and real WOT timing under a load and when you disconnect the bias to set cranking and WOT timing, then hook it back up and run it and it reads exactly as it should. Can you explain why it would make it read different if you are just timing off of the #1 cylinder?

Actually not sure if it will effect cylinder 1, but for sure will effect the other cylinders 5-8 degrees easily, and don’t think it’s good for the switchboxes. The change it has has on the other cylinders, especially 6 is why it important to index a flywheel when running on the ragged edge on timing, so you can catch a bad bias circuit before you melt number 6. Either way if it doesn’t change cylinder 1, why do it? And if it does and that’s not what it’s gonna be hooked up, again why do it?

[25two.stroke]

Yeah I was under the impression that it gave a true mechanical reading of #1 at cranking speed rather than the possibility of being influenced by the even switch box's bias circuit. And when I though to myself I asked the exact same question you just did: if it makes a difference and that the timing won't be the same when its hooked up then why check it that way in the first place. Cause if the bias is working correct in both boxes then it wouldn't make a difference. If the circuit is failing then that is when it would make a difference...and then you are right you'd be about to fry a cylinder or more. So maybe its always a best practice to check it both ways? I know it won't hurt the boxes cause each box is capable of functioning independently as long as they are grounded.

[kbahus]

Prior to putting it away this afternoon I switched the the gray wire from the top voltage regulator to the bottom and the tach seemed to straighten out, motor didnt't sound much better though. I didn't run it for long so I am going with an inconclusive test. I need to start from scratch as I did some diag last season, but nothing since as I found the trigger was bad and stopped there. Intermittent problems are the worst too, I thought for sure I had it nailed down and was happy as a clam when it was running smooth. I can ohm out the bias circuit easy, that will be the first thing I check when I get back to the boat.

[kbahus]

Started over today with ohming out bias circuit, coil packs, plug wires, and stator. I did discover my #3 plug wire was not fully seated in the coil and checked the spark plug to verify that it was not as clean as the others (brand new plugs). Must have messed that up when I set the timing which explains why it ran well and then not so well. I rechecked timing with the bias circuit hooked up as well as disconnected. I noticed that when the circuit is hooked up I am at 19* of timing and with it disconnected I am at 21* of timing. They ohm out exactly the same, I am not sure if this is an indication of a problem or not?

I then disconnected the black/yellow wires and checked for voltage backfeeding from the switch, I found .2V when cranking. Time for a new key switch as I am assuming voltage should always be zero on those wires?

From there I fired it up and ran it on the hose, it sounded good today and I am concluding the #3 plug wire must have been the problem. I used an Electronic Spcialties DVA adapter and my 20 year old Craftsman voltmeter and checked the coils to find the readings bouncing all over the place, but consistent between eachother. Time for a new voltmeter, my ancient voltmeter problably is not up to the task. I was able to further test the bias circuit, black/yellow kill circuit, and stator high and low side with no issues though.

I am considering throwing a couple updated voltage regulators at it as I have one already (the latest with the fuse). After switching the grey wires around my tach seems to be stabilized so somthing is going on there. I will replace the key switch to be safe, and hopefully get on the water as soon as the weather turns around. I have to say thanks again, this website has a ton of great info and helpful individuals!

[Whaaaaat]

Before you put a key switch in it. Check the engine and boat harnesses. I have had similar intermittent issues from a bad engine harness, water and corrosion had started in the cannon connector over the years and I had weak connections inside the connector between wires that should've been isolated from each other. Caused all sorts of issues. The kill wire had a weak connection to the run circuits, sometimes no start. Other times wonky tack signal and timing all over the place.

[tlwjkw]

one "ole fashion way" ta find intermittent electric problems is ta do it in tha dark with a well insulated screw driver...... coils, wires and plugs.

[kbahus]

Making slow progress but made it out on the water. I did end up replacing the ignition switch for the hell of it, and thuroughly checked out the boat harness and cannon plugs. While it runs well on the hose, it's not great in the water at low speeds, has poor throttle response, and low end power. I also noticed it was smoking pretty good at times and seems tempramental about trim position; I have to keep the exhaust relief out of the water or it runs poorly. Getting on plane is a struggle as when I trim it down it starts running real rough unless I can get things timed just right with the wake of the boat and keeping that exhaust port out of the water. Once it's on plane it runs great with plenty of power and great throttle response, it's like a whole new motor. I also noticed that emmediately after a high speed run and I am back at low speed the throttle response is excellent and it runs smooth for a short while then starts loading up again. I am pretty confident my ignition system is ok although I have not replaced the voltage regulators yet. I am starting to consider maybe a fuel injector or ecu problem, but can't get by how well it runs on plane. One last finding I came across yesterday while fishing was a small rainbow in the water by the motor. I replaced the pulse pump and figured it was leaking, so looked everything over and no leaks noticed, but I found a small spot of black oil nastiness down in the corner by the divider plate where the powerhead meets the adapter plate. I think the powerhead gasket is blown out causing a leak in that spot. Could this explain some of these issues? If so I guess the next step is to pull the divider plate and cylinder head covers for inspection followed up by the powerhead to replace the gaskets?

One last question, can I swap the gapless plugs over to a standard BR8HS-10 on this 2.5 150 without issue like the higher hp models? I sure would like to be able to read these plugs better.

[kbahus]

I decided to tear into the motor to see what is going on after pulling the plugs to find them all fouled and wet after fishing the other day. I figure if there is water intrusion I will see the evidence and at least take a look at the pistons and cylinder walls. I am no pro, but I didn't see any evidence of water getting in. However, I did find lots of carbon and lots of oil/fuel everywhere. The #1 cylinder wall showed a little scoring, but I think it will be good enough (open to suggestions here). I did have an even 125psi compression accross the board, but I did not do a leak down test. After seeing the the mess I decided to pull the injectors and reeds. Fuel was leaking out the lower bolts at a pretty steady rate and once I had the injection manifold off there was quite a bit of fuel resting in there. Finally I pulled the reeds since I was all in at this point and wowzers, almost every set was letting light through, some had very large gaps too. Not a ton of 2-stroke experience here, but I am assuming the reeds were root cause of my problems? Should I replace with OEM or go with aftermarket on this totally stock motor? I am going to pull the injectors and have them serviced as well as I am sure they have never been touched. Anything else I should do while this motor is opened up this far? Open for suggesions and tips!

[kbahus]

Got the Chris Carson reeds installed along with new head gaskets and thermostats. It idles a lot better and throttle response certainly improved but it is still going pig rich when I trim it all the way down and try to get on plane. Runs amazing once I break through and get on plane. Fuel injectors are my next move when I have time again.

[kbahus]

Spent some time reading through old threads and came accross the fuel pressure regulator filter screen and the symptoms were similar. Pulled the FPR and found fuel in the vacuum line, hmmmm. The screen was clean as a whistle and the regulator held vacuum. Started tracing some hoses and after some digging in the manual discovered how the VST lines route. Turns out the bleed line T-fitting was going straight to the FPR! Got the lines switched around properly and she runs like a dream now. Unbelievable, who knows how long these hoses were hooked up wrong, looked factory too. Once again, this website is a wealth of information and I appreciate all that contribute!