Need help with 1980 Mercury 200 outboard troubleshooting

[Swedish85]

We have a 1980 Mercury 200 outboard engine and having some issue and need to figure out exactly what is going on! So here is the deal.....

I mixed a little rich on the oil gas mix the last time I filled up along with adding octane boost to the mix which is where I think my #1 problem is. Also the boat went from running at low elevation to now running at around 5300ft above sea level. Not a way too much oil but probably made the mix 40/1 instead of 50/1.Also after pumping the bulb multiple times found that the fuel was not easily priming the engine. Engine would start up fine and run at idle just fine. Then when I put in gear the engine would load up and not get above 1500 rpm and then just die and not start back up. The part that sucked is this happen 3 times before and had to get towed in until I gave up.

The second time I was able to run it and was able to get to 3500 RPM and the boat ran great a high RPM's but has the hardest time getting there. But then after I stopped the boat for 15mins and tried again the same thing happen and boat died.Tried to lean out the mix, but the octane boost was still in the gas mixture for this tank.

So I clean out the plugs, blew out the fuel line, but did not replace the fuel filter and tried running on a different tank. I was able to get the boat running ok but could tell it was still loading up at low RPM's and then would slowly start to run fine at higher RPM's.

So here are my questions. Is the issue due to elevation change? Did the octane boost and extra oil jack up the fuel line? what is the best way to fix this problem to get my old 80's engine dependable again?

Thanks,
Cory

 

[CharlieB]

Re: Need help with 1980 Mercury 200 outboard troubleshooting

Such a big change in altitude is sure to make some difference in the engine performanace, and you may have to re-jet the carbs, but troubleshooting starts with the basics to ensure that the mechanical condition of the engine is sound and that the ignition is capable of operating to the required level for the engine to perform well.

Start by testing Compression on all cyl's to ensure all fall within a tight range.

Spark test using a 7/16" gap tester at cranking speed. DVA test the stator output to ensure adequate voltage to maintain that hot spark at upper RPM.

While the plugs are out testing spark, use your timing light to verify WOT timing.

Once all the above is completed then you know that all that's left is making sure that your fuel system is clean. Call a local OEM Dealer and ask about jet size changes for your altitude, look up part #'s for your model and serial at mercruiserparts.com

Once the carbs are reinstalled perform the link and synch according to the directions spelled out in your copy of the Mercury Service Manual.