Merc/Mariner/SeaRay V135 1989 Wont Idle

[gdarcy]

In desperate need of direction on troubleshooting my V135 carbed 2 stroke 1989 model year with 40 Amp stator. I own the factory manual and a DVA meter. Do not have a timing light but am willing to get one. Below is the recent history.

Summer 2020: At the beginning of the year motor was running fine started to run hot in the no wake zone but we didn't have time to do the impeller so we ran it like that and kept an eye on the temps. It never overheated. It did start to develope an issue where it would radomly have reduced RPM at high throttle even sometimes starting out at reduced RPM then all of a sudden start running with full rpm. The impeller was changed and the overheating issue fixed then the high end rpm issue got worse. At the end of the season it would run great up to 2000 to 2700 RPM just about to get on plane and just stay there steady as can be. It would run like that all day but never give us anymore. I did find intermittant spark on 1 cylinder and that switch box was replaced with no change to the way the engine ran.

Spring 2021 changed out the primer bulb and fuel line got it running on the hose but will not idle and needs some throttle to get it to start. Dies immediately when the rpms drop below 1000 often with a cough or backfire. Testing the stator I was getting inconsistent results so I went ahead and replaced it with a CDI unit. No change so I set the idle timing.

I don't even know if my high end problem is still an issue because I can't get it to idle either on the hose or in the water.

Should I be looking at this as an ignition problem or a fuel problem? How should I proceed I don't know where to go with it.

Appreciate any advice

[25two.stroke]

Post a video of it dying at idle. Sounds like you could have junk in the carbs.

That intermittent spark on #1...did that go away with the new switch box? Have you ohm'd the coils and tested the trigger output with a DVA?

The high end issue you mentioned sounds like a failing stator and that very well could have been fixed by your CDI Unit you put on. But without being able to idle like you said, you can't check. Sounds to me like you have a fuel issue.
However, you could have a failing idle stabilizer module or the red wire feeding it could be bad and grounding out somewhere. Best to disconnect that at the switchbox before trying to diagnose anything

[gdarcy]

The intermittant spark did go away with the new switch box.
I ohm checked the trigger and it is in spec. Checked my blue coils from terminals to where the plug wire connects and all 6 are close to each other and in spec.
Disconnected the idle stabilizer with no change in how it runs.
The video of the engine running and dying is here. https://drive.google.com/file/d/1n74RJnnzIqajfUsfmKuhPEIzPkx6AVFa/view?usp=sharing I had to give it about 80% throttle to get it to start. The tach was not working tonight and it was not working one other time I was doing some testing at the boat ramp. Other times it seems to work fine.

[gdarcy]

I didnt see a procedure for DVA testing the trigger just did the ohm test. Is there a procedure for the DVA test somewhere?

[merc1250bayliner]

Doesnt sound like it's running on all cylinders.

[bullet123]

sounds like idling fast on only 3 or 4 cylinders. more than likely your other switchbox is bad. Always replace in pairs. You need to start from scratch since you removed stabilizer. Get a timing light and manual for your motor. do a full link and synch. set wot for #1 at 22. set idle timing in the water by sound. there is no set number for idling timing

[gdarcy]

Thanks for the advice. Questions I have.

Would you suggest deleting the idle stabilizer and resyncing or reinstalling it.

The timing pointer lines up correctly at TDC the Manual has a procedure for setting it at .462" as well. Is that necessary? I dont have the needed dial indicator mount.

It looks like the Sierra 18-5775 is the go to switch box for this engine any alternatives I should consider?

[bullet123]

Yes, remove idle stabilizer and oil injection and any wire associated with it. premix your gas. make sure you have a bias wire between switchboxes. white/black to white/black. it ties the two boxes together. your pointer should be set from factory, leave it alone. Mallory switchboxes are about the best I have found. I think pro marine sells them.

[gdarcy]

ok so I was following the CDI troubleshooting guide for no spark issues and it had me disconnect the white black wire between switch packs. When i did this engine fired right up on second turn of the key and idled no throttle needed. Guess this confirms I need 2 new switch boxes is that correct?

[bullet123]

yes, bad bias circuit. buy two new switchboxes.

[Bodhi]

You could possibly need new switchboxes. Have you removed the boxes as Bullet had suggested yet? If so have you done the bias wire between the switchboxes?

[Bodhi]

Haha, sorry Bullet....you beat me to the send button

[25two.stroke]

Yep, you are on the right track. Switchboxes are failing on you. Get rid of all the black boxes you do not need. The motor will run no different without them.

There is a way to DVA test the trigger...I never trust ohms on the trigger or stator...but, it sounds like your trigger is not the problem.

[gdarcy]

I beleive I need to reset the timing when I remove the idle stabilizer. Is that correct? What is the proper timing? Just ordered the Sierra switch boxes.

[25two.stroke]

0 deg. (TDC) +/- 4 deg. Base Timing
21 deg. +/- 1 deg. WOT timing

That should be laid out in your manual. It may slightly vary, like saying 0-9 ATDC base timing, but the above is what I have found to be a happy place. Set base @ 0 deg. and adjust once running till the motor idles around 1000 rpms with butterflies closed.

[gdarcy]

OK so 2 new sierra switch boxes are installed bias cicuit is connected and Idle stabilizer disconnected. Starts easy idles ok although my tach still isn't working.
I'm looking at the factory manual and it lists max timing 18 deg BTDC @ cranking speed and 16 deg BTDC wide open throttle, 5-7 Deg ATDC pick up timing and 3-11 deg ATDC Idle Timing. Manual says to set Max timing adjustment first. So as I read it I should adjust the max timing stop on the throttle lever so that I get 18 deg BTDC on no 1 cylinder.

Next I'm to adjust the Primary Pickup Timing. Manual says to adjust screw to align specified throttle primary pickupmark on timing decal with timing pointer. I dont have a decal and am confused by this. Do I simply set this for 5-7 deg ATDC? Is this what 25two.stroke refers to as base timing and what should I set it to?

I understand the idle speed adjustment although it looks like the procedure goes by rpm in gear rather than timing.

Only other question I dont have the spark gap tool how do I ground all the spark plug leads?

Looking forward to getting on the water tomorrow thanks for the help.

[gdarcy]

I set the timing as 25two.stroke suggested, 0 deg pickup and 21 BTDC max. It started and idled well on the hose. Went to the lake and it started idled well and went into gear. Idle seemed a little low so I adjusted the pickup timing by ear till it was idling well about 800RPM. Unfortunately the problem I had end of last season where it wont rev up beyond 1200 RPM in gear is still present. I have a new stator(CDI), 2 new switch boxes(Sierra), and fuel pump was rebuilt last year no impact when the primer bulb is pumped. I have removed the idle stabilizer but retained the oil pump as this is a familly boat and I don't trust everyone to properly mix the gas. I'm stumped. would appreciate advice on how to troubleshoot this.

[merc1250bayliner]

Are the main carb jets clear?

[bullet123]

are your butterflies opening all the way up at full throttle? Are you sure your trigger is advancing properly at full throttle?

[gdarcy]

Yes the butterflys continue to open and the trigger advances but the engine hits the 1200 RPM level and just stays there steady no chage in the sound. The carbs were all rebuilt over the last 2 years. I havent pulled the jets to take a look but I will next time I go up to work on it. I found a procedure to DVA test the trigger so I will do that also anything else I can check? Should I just replace the trigger its not all that expensive?

[pcrussell50]

I have almost your same motor. Mine is a 1987 V150. All black boxes AND oil system removed. I’ve got it running really really well after uninstalling various bugs left behind by previous owners. I have to wonder… Since you still have the oil system, is there box that is limiting your rpm if it senses low oil level or flow? I have a carbed Yamaha 40 that I think does the same thing… reduces rpm to below 2000 under certain oil conditions. Although I never actually had that problem myself. I read it in the manual.

Could your problem literally be a bad sensor in the oiling system?

-Peter

[25two.stroke]

Sounds like you are out 3 or 4 cylinders. Post a pic of your plugs after a run.

Does the engine gradually gain power throughout the throttle range and top out at 1200, or does it reach 1200 real quick (like at 15% throttle) and then do nothing more?

FYI, if you are out a few cylinders the base timing adjustment as I noted will not be right. It will be way too high cause the live cylinders are dragging the dead ones around.

[gdarcy]

For the plug check should I run it at full throttle then cut the motor. The engine goes quickly to 1200 then stops no change in tone as the throttle opens further. The boat is in the water about an hour from my house I will go work on it tomorrow. I will take photos of the plugs after a run, a video of the engine starting and running with the throttle lingage in frame and clean the jets on the carbs. I have an inductive timing light and single spark cap tester and a DVA meter what additional tests would you suggest?

[gdarcy]

I have almost your same motor. Mine is a 1987 V150. All black boxes AND oil system removed. I’ve got it running really really well after uninstalling various bugs left behind by previous owners. I have to wonder… Since you still have the oil system, is there box that is limiting your rpm if it senses low oil level or flow? I have a carbed Yamaha 40 that I think does the same thing… reduces rpm to below 2000 under certain oil conditions. Although I never actually had that problem myself. I read it in the manual.

Could your problem literally be a bad sensor in the oiling system?

-Peter

That occured to me but after researching it there is no speed limiter circuit in the oiler system.

[pcrussell50]

That occured to me but after researching it there is no speed limiter circuit in the oiler system.

Hard luck, mate. I’ll remain subscribed to see the solution in case the same thing happens to me one day and I might be able to learn from it.

I can say that for my first few years, there were always little things that caused this motor to be usable, but a little irritating at times. Once I finally learned it and returned it as close to how it should be as possible (minus the boxes and oiling), now it really sings.

-Peter

[gdarcy]

Got up to the lake started well. Did the trigger DVA test from the cdi troubleshooting guide. Got 3.5 to 4 v on all leads to ground at idle spec is over 1 volt. Between the yellow wrapped and black leads got in the area of 4.5 m volts on each pair spec is 4 volts.
Did A run and pulled the plugs First photo 1,3,5 top to bottom. Second photo 2,4,6
Here's a video of the engine starting and idleing https://drive.google.com/file/d/1ywLce4I9uyE_7Vn0j8moFqtY_4UVqrtp/view?usp=drivesdk

Interested in anyone's take on the spark plugs.

[rprinzo]

Got up to the lake started well. Did the trigger DVA test from the cdi troubleshooting guide. Got 3.5 to 4 v on all leads to ground at idle spec is over 1 volt. Between the yellow wrapped and black leads got in the area of 4.5 m volts on each pair spec is 4 volts.
Did A run and pulled the plugs First photo 1,3,5 top to bottom. Second photo 2,4,6
Here's a video of the engine starting and idleing https://drive.google.com/file/d/1ywLce4I9uyE_7Vn0j8moFqtY_4UVqrtp/view?usp=drivesdk

Interested in anyone's take on the spark plugs.
twostroke-look familiar?
easiest test of them all: make sure your switchboxes are wired correctly,i just had the exact same issue with mine. would start and idle on the muffs, got to water,wouldnt go over 1200.plugs looked exactly like yours.had purple and white on one switchbox flipped.all the difference.just check

[gdarcy]

twostroke-look familiar?
easiest test of them all: make sure your switchboxes are wired correctly,i just had the exact same issue with mine. would start and idle on the muffs, got to water,wouldnt go over 1200.plugs looked exactly like yours.had purple and white on one switchbox flipped.all the difference.just check

That's interesting. The purple and white are trigger wires so perhaps a bad trigger even if wired correctly could have same effect. I'm out of town but will recheck wiring when I get home but really starting to think I have a bad trigger.

[rprinzo]

That's interesting. The purple and white are trigger wires so perhaps a bad trigger even if wired correctly could have same effect. I'm out of town but will recheck wiring when I get home but really starting to think I have a bad trigger.
489878my plugs before i switched wires

[gdarcy]

Went on vacation now Im back working on this. Yesterday I replaced the trigger as I had questionable DVA readings. NO change to the way she runs. Checked the wiring again cant find anything wrong. My inductive timing light shows all cylinders are firing. I'm stumped. Going to look for signs of water intrusion today and see if I can find anything.

[25two.stroke]

You don't have water in the cylinders. Some look like they just aint firing

[25two.stroke]

And it sounds horrible in the video. Make sure your trigger leads on the switchbox are all correct like bob said. If they are in the wrong place they will fire but out of time so they won't run...

[gdarcy]

Still no luck troubleshooting the ignition system so I decided to use a scope and take some pictures of the piston wash.
Below are 2 photos of each cylinder in this order 1,1,3,3,5,5,2,2,4,4,6,6
The 2 that sparked my interest are 2 and 6 I have short vides of them at the following links
https://drive.google.com/file/d/175jWg_1Pt4iAIumC13rI2I0tl6ZkdSrF/view?usp=sharing
https://drive.google.com/file/d/1tmVeJJ2A2WcyaWI6KXoR2JkaIvHKfIvW/view?usp=sharing

Anything to be learned from these? Please fire away.

[gdarcy]

Its fixed. Humbled to say the final fix came about with 6 New Spark plugs. I was seeing spark on all cylinders with induction and gap testers but it didn't seem as though all cylinders were firing. I removed all the sparkplugs attached their wires zip tied each sides spark plugs together and grounded each bundle. When I cranked it over only 2 of the plugs had good spark. Thought I had replaced them last fall when I strted my troubleshooting, now not so sure.

Thanks everyone who offered their ideas.

[bullet123]

sometimes we overlook the easy stuff. Glad you got it fixed!!

[gdarcy]

Took the boat out today and engine ran great. Was a running a little hot in no wake zone and a little cool when opened up. I plan on replacing the impeller as there was some dry cranking during my repairs. Got back to the ramp idled in tach started acting funny and it stalled when I took it out of gear. Was hard to restart then it cut out and smoke starts pouring out of the engine. Rectifier is melted. Few questions. Is this likely to have damaged any other components? What should I check before replacing rectifier? I have a new cdi 40 amp stator 174-9610K that has 2 yellow and 2 yellow/black wires and jumpers that pair them together for the 2 wire rectifier. Can I replace the single rectifier with the dual 20 amp rectifier 194-8736?