Re: trouble with 1987 force 50hp
First of all, it's a two stroke. Two strokes require oil mixed in with the fuel to provide lubrication. You'll need to mix Outboard oil, mixed 50:1 with gas. Failure to mix the proper amount of oil with the gas, you'll ruin the engine very quickly.
Diagnosing a poor idle will require tools and some troubleshooting. There is no one answer. The engine needs compression, proper air/fuel mixture of properly mixed fuel -fuel/oil, and a good spark at the right time to run properly.
Compression needs to be checked with a compression guage found at any autoparts stores or even Walmart for $25-40.
Proper air/fuel mix is controlled by the idle needles, and jets, but can be affected by air leaks, and a carb in need of new parts and set-up.
Fuel mix should be 50:1 of a TWC3 oil. The cheap Walmart brand at $11 a gallon is fine. Learn to mix it properly with a measuring cup.
Spark is generated from the stator(alternator) to the CDI box then to the coil then the plug. Each system has to be checked (most tests can be performed with a simple Ohm meter). Don't forget to start with a good battery that is fully charged and has clean solid connections.
Since you just purchased the boat and most likely don't know the true maintenence history or when this idle issue started, you'll need to check everything. Spend some money on a manual, a compression guage and a timing light. These tools will allow you to properly check the condition of your engine and set it up properly.
First thing to check is compression. Then spark/timing and lastly the fuel system. Start with replacing all the fuel lines, clean the carbs/filters, then a rebuild kit for the carbs. A new fuel pump diaphram and gaskets should be replaced as a mater of regular maintenence.
There's a thread in the Engines FAQ section titles "waking a sleeping outboard" or similar.
You'd be wise to educate yourself on your engine as much as possible. Think of your service manual as a text book instead of reference guide will provide you with the best understanding of you engine and how to maintain it.
Good luck and post your findings.
