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Outboard bogs down and dies once heated up.

D4V33

New member
Tohatsu M18E2 18hp 2stroke

This is a follow on from my last post. I thought i had a carb mixture issue as engine was running poor last week. I set the carbs and had it running nice for well over half an hour in a bucket of water.

Took the boat to the harbour today and started it up. Being that it was sitting much deeper in the water it idled a bit lower, but didn’t stall. I trawled around the harbour for about ten minutes and all steamed fine.

Once I took it out the harbour I got the boat onto the plane for about 2 or 3 minutes and it started to bog down again, so slowly headed back to the harbour where it eventually died. When trying to restart the engine I could barely keep it idling, every time i started it, it would run for about 10 seconds tops, splutter and backfire before cutting out again.

The tank has fresh fuel bought today. I measured the 2 stroke oil in a measuring jug to be as precise as possible. The fuel lines and prime bulb is new. Compression is fine.

What would you recommend I look into next?

I’ll check all the Earth wires tomorrow and see what condition the fuel pump diaphragms in.

Luckily my little auxiliary 4hp has run flawlessly for years, but hate the feeling of being on the water when things start playing up.
 
One thing I did notice, when I was cleaning the carburetor a couple of days ago was that it doesn’t have this little rubber grommet shown in the exploded part diagram. I cut one out of some sheet rubber I have and place it in the carb and the outboard wouldn’t start. Once I removed it the outboard run fine again. Again while the outboard was running I popped in the plug and it cut the engine out, so have just left it out assuming this carbs not meant to have the grommet.
Just though it was weird that it shows it in the parts catalog.
BD9D4976-FE09-412F-8174-B098A910945F.jpeg
 
Hi DAV33,

Just came across your post of May 26, 2003. I'm helping my brother with his 1993 NS18D 18HP Nissan which does exactly the same thing. I have replaced the coil, spark plugs and he has had it into a local outboard repair shop to the tune of $300. After getting the boat home and in the water he took a ride with the same result as you have described in your post.
Have you figured out the problem? If so could you message me somehow and let me know what you found out? THANK YOU!
 
Hi DAV33,

Just came across your post of May 26, 2003. I'm helping my brother with his 1993 NS18D 18HP Nissan which does exactly the same thing. I have replaced the coil, spark plugs and he has had it into a local outboard repair shop to the tune of $300. After getting the boat home and in the water he took a ride with the same result as you have described in your post.
Have you figured out the problem? If so could you message me somehow and let me know what you found out? THANK YOU!
Hi, I think it was down to a fault fuel pump. This comes as part of the carb setup on this engine, so I replaced the lot. It looks like the little metal reed type bales in the pump where not sealing properly.

I have not yet had a chance to put it on the water, so not 100% to whether this has cured the problem, but out of the water on the muffs, it’s sound and runs a million times nicer. In put the old carbs. I could probably upload a video to show the difference if I can work out how.

I hope you get your sorted (and hope this is the end of my issues too)

Regards
Dave
 
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