Early 70s 85Hp Mercury Blueband with Thunderbolt Ignition Problem

[ntnorton]

Top of the morning guys. Just putting a post in here to see if anyone has had a similar problem. I just redid a paint job on my early 70s IMC Tri Hull. Boat turned out awesome Ima post sum pics in the painting section.

Anyways onto my question. I had to take the motor off for painting so I disconnected everything...and let me say the boat ran great last year. Its an early 70s 85HP Mercury Blueband with Thunderbolt Ignition So today was my official launch day but once I got it in the water I couldnt get her to start. It would crank but as soon as she got close to starting the starter would disengage. When I use the spark advance lever all the way forward I could finally get it to start and it would rev up like crazy but as soon as you dropped her into gear there was zero power and if you even LOOKED at the choke button it would quit. At full throttle I was doing about 5mph... So my question is do I have a carb/ignition problem or did I screw something up when I reconnected my cables?

 

[Fuzzytbay]

Re: Early 70s 85Hp Mercury Blueband with Thunderbolt Ignition Problem

Questions:
Last season, did you "winterize it"?
Gas tank, poortable, or built in?
Fuel line and bulb......how old?
How long since it was last serviced, ie carb cleaning, fuel pumps, spark plugs etc?

 

[Chris1956]

Re: Early 70s 85Hp Mercury Blueband with Thunderbolt Ignition Problem

Probably not. I recommend you check for water in the gas. Take a compression test and spark test to verify all is well. If cylinders are 100PSI+ and even, and you have spark, it is likely fuel related.

 

[ntnorton]

Re: Early 70s 85Hp Mercury Blueband with Thunderbolt Ignition Problem

thanks guys, think i found the problem. when I had everything disconnected, looks like one of the kids spun the adjuster to my throttle cable all the way to the end and I didnt catch it when I hooked it back up. Reset the throttle cable and timing and now she runs like a champ again.

 

[ntnorton]

Re: Early 70s 85Hp Mercury Blueband with Thunderbolt Ignition Problem

Guess I jumped the gun to soon. Engine ran great at home in a barrel but once on the water I still only get about 5mph top speed. Seems to idle fine but once you try to put her to the woods she hits 5mph n wont budge faster then that. Did a compression and spark test, Im pushing 150 plus per cylinder and spark galore. Possibly a fuel problem Im not exactly sure. Guess I will start with a new fuel line and plugs and see where that gets me.

 

[Fuzzytbay]

Re: Early 70s 85Hp Mercury Blueband with Thunderbolt Ignition Problem

One of the reason's people spend so much money on "self repair's" is simply because they throw parts at the problem, instead of trying to diagnose it.
This approach can actually make the problem worse.
Its good you did the compression test, and checked for spark. Those are two fo the four criteria for a combustion engine to need to run.
The old plugs can tell a lot about how the motor was running. I'd get new ones, but don't install them and run the motor just yet. As for the fuel line, do you really need one? Test it first, will it prime the motor carbs, and pump the ball hard, and if you squeeze it a bit more, can you force gas pass the float, and out into the throat of the carb.
Your fuel tank can be a nightmare of problems, ones built in being the top problem causers, so do you have a portable one, or built in, you never did say. When you checked for spark, was it one cylinder, or did you check for spark on all. I take them out, ground them all, then at night, or a dark garage I turnit over, then you can see the spark, and the order to make sure all cylinders fire. I suspect your problem is fuel related, since it has the "ran last year, but won't run now this year" syndrom. However lets eliminate the electrical stuff first, since you have to change plugs now.

 

[Chris1956]

Re: Early 70s 85Hp Mercury Blueband with Thunderbolt Ignition Problem

Has that motor ever gone faster with that propeller? Do any of the spark plug wires arc to ground, when trying to accelerate?

Do any of the spark plugs look steamcleaned?

 

[ntnorton]

Re: Early 70s 85Hp Mercury Blueband with Thunderbolt Ignition Problem

hi fuzzy, hi chris thanks for the input. I decided before replacing any fuel lines to test my old ones and your right, there is NOTHING wrong with them, fuel pumps thru them fine. I do have portable tanks but they are brand new I just purchased them both on Saturday. And Chris the plugs didnt have a steam cleaned look as a matter of fact they were a lil dirty and yes last year I had no problem gettin her up into the 40 mph range. So today I came home and decided to fire it off and with the spark advance lever pushed forward it fired right off. I tried again 5 minutes later and it just spun and spun. I pulled the plugs and I had ZERO spark. I pulled the coil wire to see maybe if I had a bad coil and about once out of 10 times I would get GOOD spark otherwise I had none or maybe a spark or 2 when I would let go of the key. I know the boat has a spark module but im not sure if it has points under the flywheel or not. At least Ive narrowed it down to an ignition problem

 

[Chris1956]

Re: Early 70s 85Hp Mercury Blueband with Thunderbolt Ignition Problem

If it is a 70s motor, it likely has CDI ignition of some kind, and no points. The two major ign system on the 4 cylinder motors is battery-powered CDI with a distributor and one coil or Alternator Driven Ignition (ADI), with 4 coils.

In your case it would appear your trigger is suspect. There is a set of tests on the CDI Electronics.com website for your ignition. I sugest you investigate them.

 

[ntnorton]

Re: Early 70s 85Hp Mercury Blueband with Thunderbolt Ignition Problem. NO POWER

Re: Early 70s 85Hp Mercury Blueband with Thunderbolt Ignition Problem. NO POWER

ok guys found the spark problem, I had a faulty mercury switch. Replaced it and now she fires up each n everytime with just a bump of the key. Checked all wiring there were no cracks or hard wires, new plugs, new gas (mixed 50-1) and now 2 new tanks, carbs cleaned and for the hell of it new fuel lines. Like I said she fires right off and in the driveway & screams like a raped ape. But put her in the water and still has no OOMPH! Im getting back pressure and its not allowing my engine to wind out. Im just kind of stuck Im not sure what else to check.

 

[ntnorton]

Re: Early 70s 85Hp Mercury Blueband with Thunderbolt Ignition Problem

well guys im another step closer I believe. While I had it running today I pulled each individual plug wire off and when I took wires off cylinders 1 and 2 the engine almost died, but on cylinders 3-4 no difference. Got good compression on both cylinders so Im startin to lean torwards a bad control box. any thoughts?

 

[Chris1956]

Re: Early 70s 85Hp Mercury Blueband with Thunderbolt Ignition Problem

A timing light or spark tester will tell you if the ign is good, or if you have some other issue. The #3-4 plugs are not steam cleaned, right?

 

[Faztbullet]

Re: Early 70s 85Hp Mercury Blueband with Thunderbolt Ignition Problem

If it still has the vent lines to distributer cap remove them as I have seen them stiff and not allow distributer to rotate fully..

 

[ntnorton]

Re: Early 70s 85Hp Mercury Blueband with Thunderbolt Ignition Problem

sowwy no it doesnt have the vent lines on the distributor. The plugs dont look steam cleaned at all. Its kind of n odd thing. I have spark on all cylinders. Ive hooked a timing light up to each cylinder and it flashes fine. if you pull the plug boot off of 3 & 4 plugs you can hear the snap snap snap of spark when you hold the boot close enuff to the plug. So with spark on all 4 cylinders Ive ruled out a coil. removed all wiring and checked for cracks or tears. Cleaned up alll terminal ends of any corrosion so ive ruled that out also. beings I have spark on all 4 cylinders Ive ruled out distributor problems. All I can think of is either a stator or spark module. I just HATE to flop down 300 smackers for a module n still have the problem remain. Anyone know of a good place for used boat electronics?

 

[Moody Blue]

Re: Early 70s 85Hp Mercury Blueband with Thunderbolt Ignition Problem

Any chance you have the plug wires to 3 & 4 reversed? Could be getting good spark but at the wrong time. Would explain why not effect from removing them.

Does you engine have a single coil and distributor ?

 

[ntnorton]

Re: Early 70s 85Hp Mercury Blueband with Thunderbolt Ignition Problem

yes it is the WAY early 70s design with the single coil and distributor. I thought about the wires too but yah no such luck as it being that ez. I did find a test on the forums to test my switchbox. by removing the 3 distributor side wires and jumping the white and brown. Then checking voltage on the opposite side on both red and white wires with key off and on. Then grounding the black wire on the distributor side I should have gotten a spark and got zero, zip, zilch. I guess its a horse a piece could have been either the distributor or the box. Box is a wee bit cheaper. Now just gotta see if I can find one.

 

[Chris1956]

Re: Early 70s 85Hp Mercury Blueband with Thunderbolt Ignition Problem

If you are getting good spark on all plugs on that motor, it is not the stator or switchbox. It is has good compression, it is time to look at the lower carb.

 

[crazymac-680]

Re: Early 70s 85Hp Mercury Blueband with Thunderbolt Ignition Problem

I'm with Chris. You have seen spark and compression on all cylinders. It's a fuel problem. Most likely the carbs. You said you cleaned the carbs but did you actually remove them? Bath them stripped in carb cleaner overnight? I have the same motor and my carbs clogged up in about 4 months of sitting without use.

 

[ntnorton]

Re: Early 70s 85Hp Mercury Blueband with Thunderbolt Ignition Problem

Thanks for the help guys I really appreciate it. I too was under the impression that if I had spark on all 4 plugs my box couldnt be bad, thats why I was troubled that I didnt have spark during my test. One of my auto techs I work with said maybe I have spark when the plugs are out but not under compression but I dont think thats the case because my timing light fires great when it is hooked up and the plugs are in. I did not actually take the carbs off for a cleaning but now that you mention that bottom carb and Im only running on 2 cylinders it makes a lotta sense. Ill pull that bad boy off tnight and give her a good soaking. Thanks again for all the help guys

 

[ntnorton]

Re: Early 70s 85Hp Mercury Blueband with Thunderbolt Ignition Problem

Chris, Mac. You 2 are the bomb. Took the carbs out n you were dead on, bottom one was completely varnished up with a stuck needle. Clleaned them both up and reinstalled them and I knew my problem was fixed the second I hit the starter. Took right off and you could hear the difference. Pulled the 3/4 wires off and sure enuff lost power. Cant wait to get it on the water but before I do that I have one last thing I want to do wich is drop the lower unit and put in a new impeller. Ive read about changing out the gear oil on many posts just wondering if you guys had any idea how and where I do that at? Thanks again guys.