86 Force 50hp Running off 1 cylinder

[CaptRon29]

Hi there everyone names Ron!! Real excited i got my first (real) boat this year aside from my couple small aluminum fishing boats.. So I bought a 1971 Starcraft tri hull with a 1986 Force 50 hp and a 83 Merc 7.5 kicker and kick plate.. Both non running at time of purchase. I inspected everything including (dry) compression check on Force came up with 180 top and 165 bottom.. So not to bad since it sat from sometime in 2008 until a couple weeks ago.. So i offered this guy 300 bucks and to my surprise he agreed! So i get this puppy home and find a bad perko switch.. (Taking you all from square 1 so you know all the details sorry) I replace the battery with a large marine RV battery and direct connect it bypassing lights and acc... Engine is now cranking over on its own with no spark and the float bowl is leaking... I managed to slow the leak enough to make sure gas is getting in carb to fire, spark plugs were brand new from a previous guy who also looked at the boat, checked the coils and about everything i can see on outside with something that looked like positive and negative for continuity. All circuits seemed to be closed (good thing).. So than i get online and find out this thing has points! Holy **** batman i bet if i clean em up it will fire! So i get a puller get the flywheel off find the points and carefully take a 300 grit and gently abrase them. (did not check gaps) I stick everything back together and crank motor. ITS ALIVE! started up lickity split! Actually ran pretty good too since even the float bowl was still leaking. So first thing i do is take her down to the water and just wanna see how she does with a load right.. TO my surprise it gets up and plains with no hesitation for about 5 min than it just pukes. We do it again for about 5 min after adjust that timing rod thing attached with the throttle cable; there's a set screw adjustment i messed with. She gets up and takes off for about 10 min or so this time but again pukes out almost instantly. So I know she runs decent cool! Take it home next day go to marina get a gasket kit for float bowl including the 2 upper/lower rings around bolt. Install them and bingo no leak. Than i get new gas (premium) and add some synthetic evenrude/johnson 2 stroke oil.. heres the really awesome part.. my dumbass put 50-1 in the tank! I read it wrong and didn't realize till after i was cruising for about 10 min and it pukes out again except this time it dont wanna fire back up. I get a tow to shore get home lean the gas out with another gallon and pull plugs and crank it to get cylinders dry from access oil. I clean plugs up stick them in and now she wants to fire cool! I got it to run for a few sec than nothing but quick idle and shut off.. Hmm im thinking so i pull out the top plug and I crank the engine and boom she fires up! Ok so now im stumped why the heck? So i get online again and people talk about point gaps. Says use the flywheel timing marks 2 @ 180 degrees from each other and gap at .020 correct? Alright so again im new to this so from my understanding I have one mark with a red dash on it making me think thats primary. I turn to primary, take off the flywheel and check to see what point is open. I gap and set that one at spec than turn the the fly wheel to next mark and gap the other point. So now i have both points opening and closing opposite of each other at .020 gap. did i time it right? sure hope so... Than i go back to starting the engine and still same symptoms.. Runs off bottom plug but not top.. I actually have to take the top plug out of the head fore the engine to start! Why? So I dont want to give up and I don't have many tools along with money what should I do next? Can someone tell me exactly how to time this engine for dummies lol?

 

[Frank Acampora]

Re: 86 Force 50hp Running off 1 cylinder

Your engine ignition operates as follows: Blue wires go to positive terminal on coils. White wires go up to the points. When the points are closed, current flows therough the coils and up to the points, then to ground. When the points open, current flow is interrupted and the magnetic field in the coil collapses, inducing a high voltage pulse in the secondary windings. This jumps the plug gap.

Now: I am not 100 % certain because I don't work on these smaller engines too much any more. BUT----You appear to have an extra blue wire underneath the flywheel grounding out the points on the left of the photo. Thus: When the points open, current still flows and the coil will not generate a high voltage pulse. Try removing the blue wire connected to the capacitor mounting screw and see if that gives you spark.

 

[jerryjerry05]

Re: 86 Force 50hp Running off 1 cylinder

The extra wire is to ground the plate to the stator.
Try changing the coils around.Then if the spark follows the coil then you know the other is bad.
Try changing the condensors around it's possible the points and condensor is bad.
Coil first,then condensers.
It is 50-1 on that motor.
Please take a break between breaths.It really hard to read a post like yours.
Small chapters make it a lot easier to read.J

 

[CaptRon29]

Re: 86 Force 50hp Running off 1 cylinder

The extra wire is to ground the plate to the stator.
Try changing the coils around.Then if the spark follows the coil then you know the other is bad.
Try changing the condensors around it's possible the points and condensor is bad.
Coil first,then condensers.
It is 50-1 on that motor.
Please take a break between breaths.It really hard to read a post like yours.
Small chapters make it a lot easier to read.J

Sorry about that super long post! But thank you very much for reading it through and having a prompt response! I don't typically write in forums obviously lol.. But I read them a lot when I need help. Everything in that stator worked just the way it is now with spark on both top and bottom. I am going to come home for lunch and try exactly what you said (coils first) than ill let ya know what happens. Thanks for the help Frank!

 

[CaptRon29]

Re: 86 Force 50hp Running off 1 cylinder

So I took off the extra wire and It did not make a difference.
I chaged the coils around and no difference ethier.
Changed spark plugs nothing.
Changed fuel and added seafoam nothing.
I even scoped the cylinder and got it to TDC instead of using marks to adjust point timing... Nothing
So I take the head off and find the gasket pretty tore up..
Like any head gasket these days I would assume its supposed to be 3 piece
crush gasket.
This gasket seems to be 1 piece and had some kinda marine caulking around that as well.
I looked into the upper cylinder wall and find scoring inside where the wall comes to a opening deep inside.
A friend of a freind stated this could be normal due to being where the reeds rub?
Or is the cylinder wall supposed to be COMPLETELY smooth all the way inside and all around?
Could this be why i can only run the engine of bottom spark plug while top plug is completely removed?
So that the top piston pressure dousnt go somewhere it isnt supposed to?

 

[jerryjerry05]

Re: 86 Force 50hp Running off 1 cylinder

The walls are supposed to be smooth.Scoring usually means no compression.
Goop on the gasket also means someone knew there was a problem!!!

 

[CaptRon29]

Re: 86 Force 50hp Running off 1 cylinder

Alright so last question for now....
Do you think that it would be even worth fixing or should I call my losses
and just part this SOB out?
I keep hearing from people that my engine is the worst
boat engine i could possibly get...

 

[Shife]

Re: 86 Force 50hp Running off 1 cylinder

You time this engine using a tool that slides in through the spark plug hole. You can't get it right without it. You might get lucky and get close. I've been there and done that.

The service manual details the procedure. I cant remember the measurement, but all you need is a piece of rod to stick in the spark plug hole. Make a mark where it exits at the cylinder head when at TDC. Then make another mark for the second measurement (need to dig out my manual to see what that measurement was). This will give you your point close point. The gap only gets you in the ballpark. This measurement of the gap closing point is what acually times the sparks. You will use a test light to check the gap at this point. when lined up with the test mark, the test light should flicker. Adjust point until it does and repeat for other cylinder.

Without following this procedure, you will likely never get the timing right. I have banged my head against the wall looking for a shortcut for this and there just isn't one. A degree wheel might help, but I haven't tried that yet. The tool is easy enough to make and gets the job done. The factory tool is no longer produced.

EDIT: My 87 50 hp has been just fine as a motor. It has been dead reliable. It is not an easy engine to tune, but it is very simple to work on and parts are still widely available for most general repairs. My boat is very underpowered, so I am looking for a new OB, but not because the Force has failed me in any way.