First go at carb rebuild progress and request for advice

[SibAl]

I've just upgraded from a 4hp Tohatsu 4 stroke to a Mariner 10hp 2 stroke. It was a cheap Ebay "bargain" that was sold as spares/repairs but running. When I bought it the seller started it and it ran for a good 5-10 mins while I looked at it. He did tell me it didnt run properly and there were problems with it, but as I wanted to buy on a budget to keep SWMBO happy I went ahead. Before I would do that I made sure I had found and downloaded the manual online as it didnt come with one. I would't get an outboard without the manual to guide the work I do on it.

First thing when I got home was to start it. It ran for about 30 seconds before dying. After that it would start and die immediately, but ran a few seconds longer from cold than when I tried to restart it. So a bit of investigation and first off I found it had the wrong spark plugs in, the same plugs as the 6 and 8hp motors, but should be the same as the 15hp. So changed them but no difference in starting. I had also seen some fuel coming out of the carb when I investigated so rebuilding a carb for the first time. Next will be impeller and gear box oil change. So thats the background done, here's the rebuild progress...

I took the carb off last week and ordered the rebuild kit. Yesterday I took it apart with photos all of the way to show where and how everything fitted. One of the first things I noticed was the gaskets were all in very poor condition and came apart as they were removed. The spring on the primer/choke mechanism was missing and it looked like it has never been taken apart from new. The fuel filter and primer diaphragms dont have any visible holes but look poor condition and as I said it was leaking so I knew the gaskets needed replacing. Everything that came off went in an old take away tub and was sprayed with carb cleaner.

Today will be the rebuild. I'll add photos later.

If anyone has any advice it would be appreciated and even if it doesnt help me it might help someone else later.

[ChrisParish]

Here is what I would do:

Rebuild the carb as planned.
Drop the bottom of the leg off and sort out the impeller and gearbox before trying to start again. Alternatively attach a hose to the water inlet pipe and circulate water from the tap if you want to try and run it without the leg - just don’t turn the tap on full!

If the engine still doesn’t want to start then get yourself an ignition tester and a compression tester. You want a spark on both plugs and it would be good to see 100psi plus on each cylinder.

If you have fuel and a spark and compression then it should run.

[Martin]

If it's starting then cutting out it's probably a fuel issue.
Remove and strip the carb, clean all the jets and inspect the float mechanism. A sticking float valve will cause you lots of issues.
Old fuel leves sticky deposits in the fuel system (especially on a smoker) , if you can strip it all out and give it a good clean with carb cleaner/neat petrol - examine everything , replace duff gaskets before re-assembly.
The float valve/needle valve often gets overlooked.. make sure it has no wear, it should be a clean ^ point to the end, not a two stage worn angle.

[Andy B]

First thing when I got home was to start it. It ran for about 30 seconds before dying. After that it would start and die immediately

I'm going to say it just to tick it off the list, but did you open the vent on the tank?

[SibAl]

A couple of points to answer the posts above.

First the easy one, yes the the vent was open.

Second, I checked the fuel line was working and got as far as the fuel is getting to the carb with no issues. The carb was leaking so went straight to rebuild. Its now rebuilt and I will put it back on in a bit. I used a Repair Kit so lots of the bits were replaced with new like the needle valve, various springs, all gaskets and the fuel pump diaphragm. I think its likely that the amount of fuel leaking meant it wasnt getting through properly. I also think the float height hadnt been set properly as I've done it in accordance with the manual and it looks higher than it was before.

Impeller and gear box oil are next

[SibAl]

So time for an update. Oer the last few months I have taken the carb apart and completely rebuilt it using a rebuild kit. The carb rebuild went fairly well using the manual so I knew where every bit went.

I then went on to try to replace the impeller. Once I got the leg off I found the water tube from the intake to the impeller wasnt attached and insert with the tube coming out of the impeller housing had been pulled out and was there but not doing its job. All in all a complete idiot had been working on it and got it all wrong. Me, on my first attempt, did a far better job than the liar who told me he used to work on outboards for a club and had a marine engineer look at it as well. So I had to order a complete water pump rebuild kit that included the housing with the insert in place. It wasnt as easy to follow the manual as it was for the carb, so although there are a lot less parts I found it a lot harder. After a couple of attempts I got it built and back together.

I then realised I had a couple of screws left over so took everything apart again and did the lot again. Put the leg back on again and found that the shift shaft wasnt the right length so I couldnt put in in forward gear. Leg off again and another attempt.

Finally done and ready to try starting it. in the test bin, connect the fuel , open the vent on the tank, prime and....nothing. Bvk to the manual and set the fuel mixture on the carb and adjust the timing screw. IT WORKS. Let it run a bit, put it in gear (with the prop off at this point) and a little revving. All good, off the revs and it cuts out. Put away until today. In the bin again to test, adjust the fuel mixture again and then the timing screw, fast idle screw and throttle adjustments.

It's working well and I'm now ready to give it a proper test in the water.

My advice to anyone else wanting to try this for the first time. Make sure you have a manual telling you where everything goes and the right settings.

[rogerblack]

Well done!
It's always tough when you take on something like this for the first time, as you start right at the bottom of the learning curve. Hopefully, you won't need to do it again but if you do that experience will come in useful.