1970 Merc 9.8 (110) -- a REAL Puzzle!!

tsp1158

Cadet
Joined
Sep 17, 2006
Messages
7
I would greatly appreciate some help from the Mercury experts.

I've seen about a dozen related postings here on iboats on this motor family, and one or two had a similar situation to me,
but sadly never got an answer (from approximately 2 years ago.)

I also saw a good thread from an individual in a similar situation and it appears that after his carb rebuild, all he really needed to do was adjust his idle screw.

A few months back I bought in 1970 Mercury 9.8 110. (S/N 28484XX) It was amazingly clean and I was thrilled to purchase it.
I have run it about five or six times this month (20 - 30 minutes at mid and high speed) and while it often takes four or five pulls to start, it ran strong.

During a past weekend I went out to start it and all seemed normal at first, as I was idling away from shore the motor died.
After numerous attempts to restart I gave up... I came back in the middle of the bright sunny afternoon and tried again with no luck.
I took the gas tank out and put fresh fuel mix in - also with no luck so I pulled the motor back to my work area and looked it over.

As I pulled the plugs they seemed perfectly normal so I assumed I had a carb problem .
This weekend I opened up the carb and rebuilt it and I was surprised to see that everything is pristine except for just a tiny bit of sediment on the outside of the filter. I proceeded to remove the main jets the idle tube, and gave everything a very good cleaning. I tested the fuel pump and saw that it also works well.

After reassembling everything, I still cannot get it started.
I pulled the plugs again cleaned them, laid them against the block and verified I am getting a good spark.
I put it all back together and tried just a tiny bit of ether to see if it would fire, and it did not.
So I'm stumped, (and truly miserable!!)

I would greatly appreciate any any any guidance you may have.
I do have the Seloc manual for this motor and based on other threads I verified that the kill switch is functional and that all wiring appears to be in good shape.
In the short time that I had it the motor ran fine and has never been dropped abused flooded etc. etc.,
It did sit locked on my Jon boat for a couple of weeks but I do not think there are any moisture issues. - It has been inside for a week with the same symptoms.
I really really really do not want to pull the flywheel as we think the spark is good.

Thanks in advance for any help insight or guidance regards
? Tom
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racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
38,556
Thinking that you have good spark is not good enuff.------Rig something up so that you force the system to jump a gap of 5/16" or more.-----If it does that then you have confirmed that you have good spark !
 

gm280

Supreme Mariner
Joined
Jun 26, 2011
Messages
14,605
I concur with racerone. Auto parts store sell a spark tester and they are really cheap too. Buy one (or make one) and verify you have a GOOD spark before doing anything else. Jumping a spark plug with a mere .20 or.30 gap sitting outside the cylinder is not verification. Once it is inside there may be zero spark. So if you can verify a 7/16" jump with the spark tester then you can move to the next issue. Here is a spark tester. Cheap at most any auto parts store...
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MTboatguy

Fleet Admiral
Joined
Jul 8, 2010
Messages
8,988
Same tester I have, works great for figuring out things on a boat motor.
 

tsp1158

Cadet
Joined
Sep 17, 2006
Messages
7
Thanks Guys! Will try tomorrow night or ASAP.
My neighbor is a GM master mechanic, has a 1968 ~8 hp, also no spark so we'll work this together.
(In his case, during troubleshooting he clipped his kill switch last fall, and I explained he needs it to complete his circuit)
He's got most of the "good tools" (Flywheel puller, etc.) -- With any amount of luck, I'll get some pics and get a "how to" for iboats.
Thanks Again!!
 

tsp1158

Cadet
Joined
Sep 17, 2006
Messages
7
Success! Thanks Again Guys... I opted to buy a flywheel puller and have a "looksee."
?Points and all seemed to be in order (no discolored or cracked wires, points were a bit dark so I cleaned them with some #320 emery cloth) and they were close enough to .020 when checked so I put it back together and started right up.
I wish I had an absolute cause, but I'll let it be for now. I will order a set of points and keep them ready.
During disassembly, I struggled with the SELOC manual but took several pictures along the way.
I was a bit frustrated thinking I?d have a step by step procedure for my exact motor? I re-read the SELOC manual over coffee this morning and I can see that they try to cover every two cylinder and all 3 ignition types.
With no fear / pressure to browse the manual, it made a lot more sense today !
 
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