Hey guys, I acquired an '87 Force 15hp outboard awhile back that wasn't running. I did all the normal maintenance including: new spark plugs, cleaned the carb, checked compression (it was normal and even), and also checked the reed valves which seemed to be mostly closed but I decided to flip them just in case but had the the same results as before flipping them. I am getting spark and gas to the plugs, but it will only occasionally "pop" when trying to start it. It has tried to run for a second after the "pop" a few times. Where do I need to start now? Crankshaft seals??? Completely new reeds???

Thanks!

Check to see if there is a key way on the flywheel. Years ago, I had one doing the same thing and a mechanic replaced the flywheel key and solved problem. Think it threw the timing off before.

Checked the key off the list, I am going to try adjusting the mixture screw tomorrow to see if it is possibly too lean which is causing the pop

My advice is don't get into things you don't need to. I would have left the reeds alone unless I had reason to specifically suspect them.

On the mixture screw start by gently bottoming them out and then backing out the low speed 1.5-2 turns and the high speed 3/4-1 turn. I don't know about your experience level, but people opening up and cleaning/rebuilding carbs that aren't familiar with them cause a lot more problems than dirty carbs do a lot of times.

Make sure you have the correct plugs, make sure the are gapped correctly. My suspicion would be fuel.

Did you troubleshoot the ignition system? Not sure if '87 motor is points or CDI, but that is where I would be looking.

A failing coil will sometimes do this. Forget to mention that in my previous post.

UPDATE: I spent today adjusting the mixture screw on different settings and found 1.5 turns out to be a fairly decent spot which gave me more times of trying to fire. Attempting to start the first few tries resulted in the usual "pop", so I then applied a little starting fluid which resulted in starting and running for maybe 2-3 seconds a few times. I then came up with the idea that the fuel is getting to the plugs somewhat but not a steady flow. Checked the fuel pump and it was working perfectly. Then I took the carb off to see if there was any blockage and did a quick cleaning that blew some stuff out but not a whole lot. Stuck the carb back on, and after about two seconds of cranking and a little starting fluid, it fired up and ran for about 4-5 seconds. It fired and ran for 2-3 seconds a few other times after this. My first assumption is that I'm getting trash in the carb from the very old gas tank I am using. My next step is to thoroughly clean the carb and put on an in-line filter to see if this solves the problem.

UPDATE 2: I installed the in-line fuel filter today and tried to start it up with no luck. I checked for spark from both the plugs, and there is no spark from either one now. What the heck did I do to cause this?

Points or CDI? Need to look up how to test components. You should be able to test most with a voltmeter. Most outboards converted to breakerless ignition in the early 80's, so guessing this one is CDI. If you are lucky, you might have a wire shorted to ground somewhere.

I put new plugs on thinking I fouled the others last night. Still no spark after putting new plugs on.
This motor is point ignition

Pull the flywheel, clean and test the points. If you are not familiar with how to test them, there are lots of good youtube videos. But basically they are switches. When they touch, they short out which collapses the charge in the coil, sending a current to the plug. So, to test, when open, no continuity between point and rest of block. Coil(s) have two measurements - primary resistance and secondary resistance. Also, very easy to test. Make sure no wires are corroded, shorted, etc. as the system will short out if so.

UPDATE 3: I found out that my on/off switch had shorted out which kept me from getting spark, so I fixed that. After fixing that, I had another guy come over and try to help me get it running with no luck. We have finally decided that there must be leaks in the crankshaft seals letting air in which isn't allowing the proper amount of air flow through the carb to bring in fuel. When you place your fingers in front of the carb while cranking, there is only a light suction happening. I checked compression and it was even and normal again. So now I will replace the crankshaft seals if I can find somewhere that sells them. Any body else have any other explanations of what is happening?

Leaking crankshaft seal wont prevent it from starting.

I�m going with collapsed fuel lines and or rotten bulb. Ethanol will break down the internal linings of the fuel lines and will stop the flow like a check valve. That�s my guess and I�m sticking to it.

If you can get it to quick start with starting fluid and it doesn't stay running then you have a fuel problem. I would pull the carb and rebuild it and not just blow out with compressed air but strip it completely and remove the lead plugs and clean under them. Soak everything in seafoam for 2 days then blow every hole with compressed air.