1993 70HP Force outboard

I have just purchased a 1993 Stingray 501ZP with a 70 HP Force outboard. This past weekend I had a chance to go out to the lake and try to run the boat but ran into a problem when I had the motor at full throttle. The engine seemed to cut out on me when the RPM meter reached > 4000.

I am new to boating and to 2 cycle outboard motors so I don't even have a clue where to start looking. I am pretty good with car engines but this is all new.

When I ran the boat in my driveway at full throttle the engine did not miss a beat. The engine starts up quite nicely and has no problem when < 4000 RPM on the water and sometimes the engine would run find > 4000 for about 45 seconds then start to cut out / stall. The engine fires right back up with no problem.

I am looking for someone to give me a check list of what to check. I plan on replacing the plugs and plug wires but don't know what else to look at.

Thanks in advance
Mark

Re: 1993 70HP Force outboard

Welcome to iboats.

I would pass on the plug wires.
If you do replace them, make sure they are solid wire core, for that ignition system.

Get yourself a Clymer Force Repair manual - read it.

I'm betting it is a fuel starving issue.

Possible solutions:
Rebuild fuel pump $15
Clean carb and reset float height.
Replace fuel line and primer bulb.
Check for cracks in fuel lines going to the carb. They usually won't leak as this is a low pressure system, but they could suck air in.


other things to do:
replace thermostat
replace water pump impeller
replace gearlube

Re: 1993 70HP Force outboard

Thanks for the quick response.

I will be purchasing the Clymer Force Repair manual today and read it first chance I get over the winter months. I figure I have some time to read up on this engine before trying to solve the problem. I know that the fuel lines are new but have a question about the bulb on the fuel tank.

What warning signs should I be looking for in the bulb when running the engine? When I went to the lake I simple squeezed the bulb about 5 times and started the engine. Is that enough to get fuel to the carb? Should the bulb be hard when running the engine?

Also is there anything I can do to check for this problem in my driveway? Right before I purchased the boat I previous owner ran the boat in the driveway for me and it ran fine at the top end.

Mark

Re: 1993 70HP Force outboard

Running at full RPM out of the water is NO LOAD. It takes very little fuel, timing advance, and carb opening to reach high RPM. Therefore unless the engine is run in a bucket with a test prop, almost nothing can be diagnosed by running in the driveway. The only thing it will tell you is that the engine will start and run. Most will start and run even with a burned piston--Don't worry, I'm just using that as an extreme example, not saying that you have one.

Sure does sound like it is running out of fuel at full throttle.

Just check the fuel from tank pick-up to carbs to see if there are any partial clogs, Change the diaphragm in the fuel pump, (valves too if it is a square Merc pump) and perhaps, if that doesn't help, then clean the carb.

Re: 1993 70HP Force outboard

The previous owner did mention that he needed to change the diaphragm in the fuel pump one per year. I will check that and get back to the group as soon as I get a chance to check out the engine.

Is there any way to tell if the diaphragm is bad by looking at it?

Thanks for the help
Mark

Re: 1993 70HP Force outboard

Ok so I have rebuilt the fuel pump and ran the engine in my driveway. While running the engine in the driveway I pushed on the spark plug wires (to make sure they were seated) and I noticed that the #1 cylinder was giving me a mild shock. I pulled the plug wire and noticed that the wire was cracked so I am sure I need to replace the spark plug wires but I don't know what to buy. What model number/type of wires should I get?