New guy here with minor question

**CarlCVX20** · 06-14-2021, 08:28 PM

Does it make sense to swap the connections of the two boxes and run it to see if the #2 fires or not? If the no-fire moves to the #1 then the box is bad, if the no-fire stays on #2 then I need to investigate further... possibly the trigger. Does this make sense?

**flabum1017** · 06-15-2021, 06:41 AM

Yes, possible trigger too, this is why we test everything first. I've seen mechanics replace the switch boxes, coils and stator just to find out they had a hole in the block..... (extreme, yes, but true)

So one step at a time.... get yourself a DVA adapter then start fresh.

**CarlCVX20** · 06-15-2021, 07:11 AM

I understand that proper diagnosis is a process. And with limited equipment this can be difficult. I thought I was lucky enough to have figured this out when the one switch box had bad resistance readings compared to the other one. Could that just be a red herring?

**rprinzo** · 06-15-2021, 08:54 AM

Originally Posted by CarlCVX20

I understand that proper diagnosis is a process. And with limited equipment this can be difficult. I thought I was lucky enough to have figured this out when the one switch box had bad resistance readings compared to the other one. Could that just be a red herring?

you know to get accurate ohms readings, whatever your checking needs to be isolated,if theres wires hooked to it ,the power the meter uses to send to check resistance could head elsewhere

**CarlCVX20** · 06-15-2021, 09:59 AM

Originally Posted by rprinzo

you know to get accurate ohms readings, whatever your checking needs to be isolated,if theres wires hooked to it ,the power the meter uses to send to check resistance could head elsewhere

Agreed. As per the CDI troubleshooting guide, I removed the black/white wire that’s connected to both boxes before I did my ohms testing. Got two very different readings, one was in spec the other was not.

**25two.stroke** · 06-15-2021, 10:04 AM

To that question abotu spark...if you find it does have spark then do a compression test on that cylinder. If it has spark and compression then I would suspect one of two reasons as to why it is not firing: too much fuel, or bad reeds. Busted reeds it can't suck fuel into that cylinder, and too much fuel (like if a carb is overflowing) will wash out the cylinder and look clean.

**CarlCVX20** · 06-15-2021, 04:51 PM

A lot of what everyone is saying is starting to sink in, so I went to my local auto store and picked up a spark plug tester. Unfortunately it’s only an in-line unit but I think it will still shed light on my issue with the merc. I will do some testing tomorrow and report back.

Again I value the advice and insight you all have provided.

stay tuned.

**25two.stroke** · 06-15-2021, 05:02 PM

Grounding the plugs to the block and watching can often be better than using the tester. Because not all spark is the same...there might be enough power to light a light but not enough to fire a spark under compression. Weak spark is just as good as no spark. Seeing any indication, however is a good start. But don't ever rule out an ignition issue if you see spark in each cylinder. These ignition systems are funny in a way (but there are even more complicated ones out there too, like optis when one coil fails it keels the cyl. next to it).

**flabum1017** · 06-15-2021, 07:10 PM

An air-gap tester is the best to use since they tell you the spark should jump at least a 1/2" air gap

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**CarlCVX20** · 06-16-2021, 03:51 PM

Welp, there’s at least some spark on all cylinders. I say at least because it’s bright outside and it was hard to see the tester light up on some occasions. On cylinders 3-6, the tester seems to have lit up brighter than on 1 and 2 and I’m fairly certain those two didn’t always light up with every turn of the ignition. What I am certain of is that all 6 lit up at one point or another during the testing.

on a side note, can over-tightening a waterpump housing keep the motor from reaching full rpm?

**25two.stroke** · 06-17-2021, 02:14 PM

Originally Posted by CarlCVX20

Welp, there’s at least some spark on all cylinders. I say at least because it’s bright outside and it was hard to see the tester light up on some occasions. On cylinders 3-6, the tester seems to have lit up brighter than on 1 and 2 and I’m fairly certain those two didn’t always light up with every turn of the ignition. What I am certain of is that all 6 lit up at one point or another during the testing.

on a side note, can over-tightening a waterpump housing keep the motor from reaching full rpm?

No.

There is nothing you can do to the water pump that will affect WOT rpm.
Melt it
forget to put it in
put no keyway in
put no slinger in
fill it full of epoxy
pack it full of grease

your motor will spin it no matter what.
We always put a slight film of grease in the impeller cup on water pump changes. Not sure how much it does, but we do it. We tell customers to do the same in case you start it dry or whatever, I think it saves it for a min. The other day some customer thought, " well if a little grease is good for it, then a lot must be better" ... he packed it with grease like a wheel bearing. Then he complained it wouldn't pump....I wonder why. But it did not hurt anything when he cleaned it all out.

**racervboat** · 06-17-2021, 03:05 PM

Originally Posted by 25two.stroke

No.

There is nothing you can do to the water pump that will affect WOT rpm.
Melt it
forget to put it in
put no keyway in
put no slinger in
fill it full of epoxy
pack it full of grease

your motor will spin it no matter what.
We always put a slight film of grease in the impeller cup on water pump changes. Not sure how much it does, but we do it. We tell customers to do the same in case you start it dry or whatever, I think it saves it for a min. The other day some customer thought, " well if a little grease is good for it, then a lot must be better" ... he packed it with grease like a wheel bearing. Then he complained it wouldn't pump....I wonder why. But it did not hurt anything when he cleaned it all out.

Post #25 is pretty funny chit as to the water pump housing torque.
Packing it full like a wheel bearing is classic.hahaha I always coat an impeller with a slight film of grease helps it turn in better especially on a omc with the rubber string gasket.
If I loosen my pump housing on my drag motor I might gain a mil of a second before I burn a piston.