1972 mercury 9.8 will not start

[paddlen]

Hello: My 1972 mercury 9.8 model 110 S/N 3268781 ran perfect for the last 10 years this summer it quit. The low speed coil pooched so I replaced both high and low.And thought while in there changed points (.020 gap) and condenser.No start.So I changed one ignition coil cleaned carb (mixture screw 1-3/4 turn) new fuel pump kit and this thing will still not start .I am getting no fuel at plugs (dry) I did the "never do " and sprayed carb with quick start and throttle open and in gear and it did flash for about 2 seconds .
So I did spray carb with fuel mix "no go" and spray cylinder hole and still no go . Please help I don't like paddling.

 

[jbjennings]

Re: 1972 mercury 9.8 will not srart

Re: 1972 mercury 9.8 will not srart

If you sprayed fuel mix in the cylinders and carb throat and it won't start, either your plug wires are crossed, you're not getting spark on either, or the timing is off. I'd check to see that the wires aren't crossed and do a spark check with an actual spark tester to see if it will jump a 1/4 inch air gap. There's probably no need to check compression, but........
JBJ​

 

[paddlen]

Re: 1972 mercury 9.8 will not start

mr. JB thank-you for responding to my plight.
Compression on this 9.8 is 105 each hole spark is quite strong with a spark tester and the plug wires are correct. I have I believe enough vacumme from carb and good pulse to fuel pump.I have even pressured each cylinder and do not have air leakage so I assume rings are good This really has me stumped.
I have tried almost everything except a tear down.But sombody out there knows somthing I don't and I hope its easy(and possibly humbling) thanks again.

 

[Wingedwheel]

Re: 1972 mercury 9.8 will not start

I believe this question was asked, but did you check the timing?

 

[da_n24]

Re: 1972 mercury 9.8 will not start

Have you thought about those little magnets up in the pull rope assembly?? I know sometime those little wires, or the clips on them will break.

 

[paddlen]

Re: 1972 mercury 9.8 will not start

The timing is hard to check witout it running but I pulled it over and my son held timing light and cyl one and two flasned on TDC. As for the magnets under the cover I believe you are refering to the high and low speed coils and thes are new.Why do we love these old Mercs and try to keep them running forever ?

 

[jbjennings]

Re: 1972 mercury 9.8 will not start

Switch the plug wires and see what happens.
JBJ

 

[Laddies]

Re: 1972 mercury 9.8 will not start

One of the most common problems with the smaller engines with phazer points is the insulator blocks on the points crack and short out the problem is not visable in most cases and is a amost a sure result if points are changed without the blocks being changed.

 

[paddlen]

Re: 1972 mercury 9.8 will not start

I have tried to switch plug wires even when I knew they were correct and just switched them even if it ran poorly at lest it ran,but it did'nt.
Other wise I have great spark jumps a 1/4" gap no problem.Could the point blocks still be cracked? They looked good when points were changed but maybe I did not look well enough.Could this be a reed problem even though I am getting good vacumme through carb?

 

[bktheking]

Re: 1972 mercury 9.8 will not start

This was a 7.5 I worked on in the summer, the cause was cracked insulators and 2 bad coils.

 

[Laddies]

Re: 1972 mercury 9.8 will not start

Yes, and the cracks are seldom visable as in the photo, the points are a high voltage ground so even the slightest crack will arc.

 

[paddlen]

Re: 1972 mercury 9.8 will not start

If the blocks are cracked would I still get great spark 1/4 inch gap and it seems strong .My concern is the dry spark plugs .Last night I checked fuel pump again and it works well and good pulse from pulse line .The carb is clean and spark seems good (I will check insulaters again) and 105 comp. each hole,and carb seems to have good vacumme .I just cannot figure this out.

 

[paddlen]

Re: 1972 mercury 9.8 will not start

you guys are good ! I took took the flyweel off again and point insulator for #1 cyl has very fine crack right where strap for points about 1/16" from hole .
I hope this is it now I need to order them (Here in about 3 weeks) .I will keep you guys posted .Thanks again.

 

[bktheking]

Re: 1972 mercury 9.8 will not start

Where did you find them, I bought the last 2 from East Coast Marine? I thought maybe CDI sold them seperate from the stator but there was no part number. This was the EXACT problem I had, the 1 coil was broken by the owner, I put 2 used ones on and still had very little spark. The points are the trigger and if they aren't isolated properly from ground good spark will never happen.

 

[paddlen]

Re: 1972 mercury 9.8 will not start

One of the mercury dealers here said he can get them maybe I should get him to check stock before I wait 3 wks for nothing .merc#336-4460 after market is just p/n 4460. If this works this Merc might outlast me ..

 

[Laddies]

Re: 1972 mercury 9.8 will not start

CDI part number 994-3981

 

[paddlen]

Re: 1972 mercury 9.8 will not start

insulaters were shipped from mercury Dec /4/10 and should be here soon.
It has been a long wait and I hope worth it I will let you know what happens

 

[WOJO 1]

Re: 1972 mercury 9.8 will not start

Just for conversation sake. What, if any intermittent problem might one see if the engine IS running but one or both of the insulator blocks are crakced?

 

[bktheking]

Re: 1972 mercury 9.8 will not start

It simply won't fire properly. You'll either see really weak or no spark at all which will lead to fouled plugs or the motor running on one cylinder or perhaps hard starting.

The plugs used in these motors are surface gap plugs, they require much more current to spark properly than a conventional magneto system, that's why they have points that are 3 times the size as standard points and a stator to drive the coils. The points simply act as a timer to fire the coils. If the insulators are cracked the voltage will leak to ground.

If you look at CDI's site they explain the test for this system. I did the test and everything pointed back to the insulators, that's how I figured it all out, process of elimination and some good advice from a gent on john's old merc site.

 

[WOJO 1]

Re: 1972 mercury 9.8 will not start

bktheking, thanks for the response. That is not the symptoms mine has so I guess the insulators are good.