Merc/Mariner/SeaRay V135 1989 Wont Idle

**gdarcy** · 06-21-2021, 01:44 PM

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** · 06-21-2021, 01:59 PM

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** · 06-21-2021, 06:54 PM

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/1n74...ew?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** · 06-21-2021, 06:57 PM

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** · 06-21-2021, 08:05 PM

Doesnt sound like it's running on all cylinders.

**bullet123** · 06-22-2021, 04:49 AM

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** · 06-22-2021, 07:41 AM

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** · 06-22-2021, 07:56 AM

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** · 06-22-2021, 09:18 AM

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** · 06-22-2021, 09:29 AM

yes, bad bias circuit. buy two new switchboxes.

**Bodhi** · 06-22-2021, 09:34 AM

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** · 06-22-2021, 09:38 AM

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

**25two.stroke** · 06-22-2021, 10:16 AM

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** · 06-22-2021, 12:02 PM

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** · 06-22-2021, 12:09 PM

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.