Mercury V6 150hp outboard - need help getting it running

[DanH]

I picked up a different compression gauge based on your recommendations. (Innova 3612 with valve in the spark plug end.)

Very different results this time. I'm not sure what to make of it. Perhaps there is still a link/sync or ignition issue...

#1 = 105, 105
#2 = 120, 120
#3 = 118, 115
#4 = 130, 120
#5 = 110, 110
#6 = 120, 120

[Glastron1987]

Compression appears quite adequate.

[Glastron1987]

Isn't there a ground wire for each coil? Or did you already check that?

[DanH]

I did check each coil ground. All good.

[DanH]

How did you ID this motor as an XR2? What is the main difference between XR2 and not?

[rock]

Those compression numbers had to make you feel a bit better. XR2 is most likely a couple degrees advanced and possibly a couple cc less chamber. I think they also had a different gear case.

Rock

[DanH]

Peter,

1) I purchased and installed the ignition parts myself. Stator and trigger are by CDI Electronics, new switch boxes are "cheap" ones with clear potting (Kemimoto brand). The sb's I took off are not the original ones but I think I will reinstall them and test everything again. The old ones are dated 6/8/2010, with black potting, marked 8M0028851 ID-P7. Do you know who might have made them? Ignition coils and plug wires are new from Sierra. Switch box to coil harness is new from CDI Electronics. Spark plugs are new NGK BU8H (no gap adjustment). Rectifier is new from The ROP Shop.

2) I cleaned the carbs myself. I cleaned them with carb cleaner and blew them out with compressed air. New gaskets and needle/seats (Sierra). Floats are just about level with the bowl when held upside down. There are no screw adjustments on these carbs. I don't know if the carbs are original to the motor. They are marked WH-33. Jet sizes are 056 (idle air bleed) and 064 (main). I am at about 1200' elevation in generally warm/hot weather. There are no fuel bowl jets installed in these carbs (I did not remove them, this is how it was). I've read that the motor can be run safely without the fuel bowl jets(?) I'm not sure about that.

3) My mechanic is me (maybe that's the real problem! LOL!). The motor revs up fine on the hose (as high as I'm willing to do it!) The boat will idle in gear at the lake just fine. But move the throttle forward to accelerate and that's when it bogs/dies. No power. To me, it acts like there's too much or too little fuel or an ignition/timing problem. That's why I focused on these systems so much. It could very well be the linkage adjustment. I also tried to lightly blow air thru the fuel enrichment valve (both lines) and no air went thru - so I don't think it's letting extra fuel thru while closed.

4)The Seloc book is a bit vague on linkage set up. I will try to post a video of the linkage going thru its range of motion. If there's an issue with it, I'm sure you guys can spot it!

I made sure all carb blades (butterflies) open and close at the same time. I lined up the marks on the throttle cam with the center line of the roller. In the neutral throttle position, there is a very small gap between the roller and cam meaning the carb blades are fully closed. It's at minimum timing at this point. Same at idle while in gear. Timing is still at minimum. At full throttle, the carb blades are fully open with a very slight amount left so that the throttle stop is stopping the travel rather than the carb blades themselves. Full timing advance is in at this point. The link between the timing arm and trigger is set to the 11/16" (17.5mm) distance. If you have better linkage adjustment instructions, definitely let me know. I will work on that video.

5) I had the reed blocks out while the motor was apart. They looked good - at least nothing obvious. I did not disassemble the reed blocks themselves, I cleaned them lightly with brake clean and low pressure air and put them back in with new base gaskets. I would like to (and probably will) install CCMS fiber reeds.

Thank you very much for your advice!

Dan

[DanH]

video - let me know if this link works

https://youtube.com/shorts/UDMMr4r7o6A?feature=share

[OnPad]

Video works for me.

Might lube everything up, kinda looked like your idle timing moved a little bit if you watch the video a few times in a row. You might also bump your idle timing up just a little bit.
Wont be able to fine tune till you sort out your no spark on cylinder six.

[DanH]

I swapped in the old switch boxes and now have spark jumping the gap on all 6.
DVA reads 135 to 155vdc on all coils.

[OnPad]

Check this photo out. A fellow last year was having problems after rebuilding his carbs. Some aftermarket needles have a excessive gap in the wire hanger, making it really hard to get your float bowl level correct. He eventually closed the wire gap up like stock needles.

[pcrussell50]

3373035[/URL]]I swapped in the old switch boxes and now have spark jumping the gap on all 6.
DVA reads 135 to 155vdc on all coils.

I don’t know if that alone is enough to account for your problem … Hopefully it is though. Take her out and let her rip and report back what you find.

-Peter

[Glastron1987]

I swapped in the old switch boxes and now have spark jumping the gap on all 6.
DVA reads 135 to 155vdc on all coils.

That is an excellent finding. If you still have problems after this, then I would focus more on fuel issues.

[DanH]

Thought you all might want an update on this motor. I ended up taking it to a local shop. They said it wasn't firing on all 6 cylinders. They replaced the #4 ignition coil and said it is running great now. I thought this was strange because I saw spark on all 6 cylinders with a 1/4" gap tester and the coils were new.

So I checked the resistance on the new coil so I could compare it to the others. I took three measurements: input-to-ground, input-to-output and output-to-ground. Input-to-ground was about 0.2 ohms. The input-to-output and output-to-ground measurements on the "new" #4 coil were about 250 ohms. The coils I had purchased read about 450 ohms, and one was 1350 ohms. I did not expect that much difference.

I went ahead and ordered 5 more "Sierra" coils. The resistance measurements on those matched the #4 that the shop installed (which I believe was made by Sierra). Lesson learned - cheap (Amazon) ignition coils are no good.

The boat has been out on the water a couple of times and it is running very well so far.

Thanks for all the help!