Logo
FULL SITE MENU

75

"It's old and it's a M

"It's old and it's a Merc


1973 model, had the early Thunderbolt 2 ignition (so still has points). The model run changed a little over the years (updated ignition and carb) and it stayed into production until 1985.

The 7.5's with the Thunderbolt 4 ignition are considerably more desireable (post 1976 models).

They shared a most components with the model 110 which later simply became the 9.8...."
 
"This is actually good news. I

"This is actually good news. I had an earlier post of my "73" 9.8HP with no spark. After ohmming it out last night the only reading coming up odd was with the high speed coil (110 ohms) If I had the right info it should have been around 450-550 I beleive. Not sure if that is the source of my no spark. Any way the above mentioned 7.5 is the same vintage and as long as it runs or at least has spark, I can get back on the water. Thanks for the great info from this post and my earlier ones as well. Good place to find troubleshooting tips."
 
"Gary, less resistance isn&#39

"Gary, less resistance isn't always bad - indicates no break in the winding - more resistance is the big problem. Additionally, simple temperature changes can throw those ohm readings out the window.

I tend not to rely on ohm readings that are out of range. Ohms are best used to simply check for continuity or no continuity.

If the continuity is at least there, then I will test with a DVA for the correct voltage.

From your results your high-speed coil is actually conducting things a little "better" than spec which is not a bad thing on that particular component (it would be on a stop or bias circuit).

So simply based on that reading, I would suspect something else is the problem...."
 
Do you have a chart or know wh

Do you have a chart or know where I might look for one that would tell me what the correct voltages should be?
 
"I don't - just been diggi

"I don't - just been digging through what little I have in (paper) manuals for the type II ignition. It gives me the ohm charts and then goes on to say that further tests need to be performed by an "ignition analyzer" but does not give chart readings for that.

From the notes I have (left by my father who worked on motors with points)
the common point of failure on these ignitions was the condenser (capacitor)."
 
"Will try some other test to c

"Will try some other test to confirm, but if I remember from previous posts the capacitor is no longer available?"
 
"No, not from Merc and not fro

"No, not from Merc and not from a few of the other places that sell "new old stock", so would be an item from a recycler."
 
Back
Top