Nissan 6 HP 4 cycles

[Orca]

Above was in reference to the the question some time ago about the zinc. In a more general review of the Tohatsu/Nissan/Merc 6 HP I will say that they seem to have really small jets and I am having trouble keeping the motor running more than 4 weeks. I started the season with new gas after having had the engine serviced for trouble last season. I treated with Stabil Marine and within 4 weeks the carb was clogged with white mush. I cleaned it a few times and used Sea Foam. It started running again but 4 weeks later it was so clogged that I took it to a marina along with the line and the tank. They pronounced my gas fine, cleaned the carb and now 4 weeks later the carb bowl has white mush in it again and the motor wan't run. The marina talked me out of using aviation 100 low lead saying it would clog the rings but if I get that thing going I'm switching to ave gas and if that fails I'll sell that and move on. Which which other motors fit because I've had enough of this one? I didn't have much time to use it so basically this ruined the season. I've had guests waiting on board the last few times which we aborted when the motor wouldn't run. Basically we can't make a motor on its third season run more than occasionally. I'm going to take the carb off the old tohatsu with the ruined lower unit and try to make it to the marina to pull out for the season. AAAGH!

[pbryant]

Above was in reference to the the question some time ago about the zinc. In a more general review of the Tohatsu/Nissan/Merc 6 HP I will say that they seem to have really small jets and I am having trouble keeping the motor running more than 4 weeks. I started the season with new gas after having had the engine serviced for trouble last season. I treated with Stabil Marine and within 4 weeks the carb was clogged with white mush. I cleaned it a few times and used Sea Foam. It started running again but 4 weeks later it was so clogged that I took it to a marina along with the line and the tank. They pronounced my gas fine, cleaned the carb and now 4 weeks later the carb bowl has white mush in it again and the motor wan't run. The marina talked me out of using aviation 100 low lead saying it would clog the rings but if I get that thing going I'm switching to ave gas and if that fails I'll sell that and move on. Which which other motors fit because I've had enough of this one? I didn't have much time to use it so basically this ruined the season. I've had guests waiting on board the last few times which we aborted when the motor wouldn't run. Basically we can't make a motor on its third season run more than occasionally. I'm going to take the carb off the old tohatsu with the ruined lower unit and try to make it to the marina to pull out for the season. AAAGH!

Be sure to disconnect the fuel tank line from the engine at the end of the day and allow the engine to run until the bowl is emptied and the engines stops from fuel starvation. The owner's manual actually recommends this. The procedure accomplishes two things: it allows the engine some cool-down time to reduce thermal shock and -- more importantly, it empties the carb bowl so the fuel doesn't evaporate in the bowl every time you run the engine and eventually develop a residue.

100 "low lead" ("100LL") av gas should really be called: 100 lots of lead. It has more lead than leaded car gas once had. It will foul your plug. Yes, 10% ethanol gas will absorb water, but I doubt the water content is causing the fouling.

[Orca]

Be sure to disconnect the fuel tank line from the engine at the end of the day and allow the engine to run until the bowl is emptied and the engines stops from fuel starvation. The owner's manual actually recommends this. The procedure accomplishes two things: it allows the engine some cool-down time to reduce thermal shock and -- more importantly, it empties the carb bowl so the fuel doesn't evaporate in the bowl every time you run the engine and eventually develop a residue.

100 "low lead" ("100LL") av gas should really be called: 100 lots of lead. It has more lead than leaded car gas once had. It will foul your plug. Yes, 10% ethanol gas will absorb water, but I doubt the water content is causing the fouling.

I only ran the motor twice after the carb was serviced and I ran it dry. I disconnected the fuel line and tank and put them down below on the cabin sole in case water was permeating the line or something. I've been running 100LL in my scooter for about a month, I'll pull the plug and see what it looks like. Quite honestly if 100LL cut the life of my motor by 30% I'd never notice it. I seems like it would last a real long time never running which is the present situation. A plug would be easy to change, carb, not so much. I did think of keeping an extra carb on board though as its a real pain in the butt to load that motor into a dinghy from my mooring and row it to the beach.

[pbryant]

I only ran the motor twice after the carb was serviced and I ran it dry. I disconnected the fuel line and tank and put them down below on the cabin sole in case water was permeating the line or something. I've been running 100LL in my scooter for about a month, I'll pull the plug and see what it looks like. Quite honestly if 100LL cut the life of my motor by 30% I'd never notice it. I seems like it would last a real long time never running which is the present situation. A plug would be easy to change, carb, not so much. I did think of keeping an extra carb on board though as its a real pain in the butt to load that motor into a dinghy from my mooring and row it to the beach.

I installed a "Racor SNAPP One-Piece Snap-In Fuel Filter Water Separator - Filter Assembly w/ Bracket & Drain - 2 Micron" between the fuel tank and the engine two years ago. It has a clear bowl that allows you to see if any water has accumulated. Pilots will know this device as a "gasculator." They're common on most airplanes. I have yet to see one drop of water in the inspection bowl. But it made me feel good to install it.

The engine problems I had were:

1) I failed to recognize that after the engine is shut down while bouncing around in swells that the fuel would run down hill out of the carb bowl back to the tank - making me pull the cord about 10 times before the fuel pump would refill the bowl. Solution: squeeze the primer bulb until it's "stiff" before restarting the engine.
2) Since my fuel tank is slightly below the carb bowl, fuel doesn't feed the carb by gravity. The fuel pump MUST be able to draw against a partial vacuum to be effective, and... I wasn't getting an air tight seal where the fuel line connects to the tank. Solution: clean the connection at the fuel tank regularly with a wire (bronze) brush.
3) The fuel cap was a fancy CARB (California) approved type that required a partial vacuum in the tank before the air vent would open. That vacuum was too great to allow fuel to flow. Apparently, California thinks a few fuel molecules evaporating out of the tank is a major source of pollution. I discovered this after the engine died about a dozen times -- always obeying Murphy's Law by failing at the harbor entrance, near rocks, while crossing in front of big boats, or on final approach to my slip, -- and I finally saw the sides of the plastic tank pop out when I removed the fuel cap - along with a loud whooshing sound when air rushed into the tank. Temporary solution: screw the cap on very loosely. Permanent Solution: Find an old-style cap that fits the tank that has a simple non-pressure controlled vent (please don't report me to the CARB).

I have about 300 hours on my engine, using 90 octane / 10% ethanol fuel (it does seem to like 90 more than 87 octane - but that might be my imagination), and I've had no problems yet besides the problems above that someone smarter than me would've spotted sooner. I always let the engine run out of fuel at idle throttle at the end of every sail.