1992 Mariner 2.5 horsepower problem and questions - The Hull Truth

coachlaw · 04-23-2008, 01:11 AM

I picked up this little motor yesterday. The owner said he could not get it to start. It has compression, spark, and fuel, all the elements are there, but no workie. He said he had also cleaned the carb hoping that would get it to run. I looked at the front of the motor and mentioned that it probably just needed a key fit into the kill switch. He said it had run before without such a key. I have no reason to think he is lying, but sometimes people's memories are faulty.

So before I start messing with the thing, does this outboard have or need such a kill switch key? If so, that's probably my easy fix. It has a kill button on the front and with other similar motors I've owned or own, a plastic key fits there. I pulled the key off my 1991 Nissan 8 horsepower and tried it, but it doesn't fit.

I've looked all over the net trying to find info on this motor, but I couldn't find anything. Thank you! - Coach

A1 Outboard · 04-23-2008, 05:22 AM

Start by visiting a Mercury dealer and getting the correct "key" for the kill switch.

Mercury's (Mariner) small motors were built by Yamaha or Tohatsu and you might find parts at one of those dealers if they are local.

Most commonly, a motor that has been sitting for a long time will have varnished up carburetor, fuel pump, and, if equipped, fuel filter. Even if someone says they cleaned the carb, they usually mean they sprayed something down the throat. Most of the time a carb has to come apart, be soaked in approved cleaner, and a new carb kit installed.

Your first and easiest troubleshooting check should be a compression test and a spark test. The quickest test is to see if there is spark at the plugs while pulling the motor over.

coachlaw · 04-23-2008, 08:39 PM

A1, thanks so much for your reply. I went out and purchased a compression tester. Looks like it gauges a 45-48 in compression. Is that good? I can't find anything anywhere that says what the compression should be.

I also turned the lights out and looked to see if I could see a spark when I pulled it over. No spark visible. I looked closely and found that the spark plug was really big for a motor this size so I got on the net and found a PDF manual for a Tohatsu/Nissan 2.5 horse motor. Are these the same? They look identical to this Mariner. I looked up the correct spark plug for the Tohatsu/Nissan and went and got one. It is a RL-87yc, which is the third choice in the manual, but it's the only one the parts place had. The new one is quite a bit longer in the threads, perhaps a quarter of an inch. I plugged the new one into the wire and it fits way too loose, actually falling out. I'm thinking the previous owner jammed the too big spark plug into the wire receptacle and deformed the clamp inside. I did not try to us a pair of pliers to crimp it tighter because I'm afraid of messing it up. I also have to still wonder if this is the correct plug for this motor. The plug in it was a Champion L86C and as I said, it did not produce a visible spark. Of course the reason could be that it might need the key clamp to fit into the kill button groove. I am not certain yet if it needs one or not. I reckon on a 1992 model, it should have a kill switch though.

So what is my course of action? The closest Merc dealer is over 30 miles away, which is quite a hike for me. Again, thank you so much for the help. I'm new to this site and I'm really impressed so far!

A1 Outboard · 04-24-2008, 06:35 AM

Compression numbers look low. I'm not familiar with that particular motor but I would assume it should be in the 70 psi range or better as other small engines are.

Without seeing the sparkplugs and threads, your best bet is to talk to a Merc dealer and have the serial number handy.

coachlaw · 04-27-2008, 05:18 PM

Well, I just got a spark tester and it has a great spark. I tested the compression again, this time screwing it in all the way. After the prescribed 5 pulls, it registered a 60. I put the plug back in, opened the fuel vent and fuel valve and pulled. I got it to sputter, but it was just barely a sputter. After about 5 minutes of aerobic activity, I pulled the plug and sprayed a gas/fuel mixture into the cylinder. No sputter this time. I just pulled and pulled, trying all sorts of throttle and choke combinations. Unless you can think of anything else I should check, it looks like a trip to the Merc dealer is in the works. By the way, it did not need a kill switch key.

A1 Outboard · 04-27-2008, 08:18 PM

Quote:

coachlaw - 4/27/2008 7:18 PM it looks like a trip to the Merc dealer is in the works. By the way, it did not need a kill switch key.

My guess is the carb is varnished up and that someone either disconnected the kill switch or the switch is corroded and faulty.