Mercury 6HP 4 stroke stalls under load

"Unfortunately, I bought a 200

"Unfortunately, I bought a 2002 Mercury/Tohatsu 6HP 4 stroke outboard a few years ago. It ran great for one season.

Now this year, when you give it some throttle, and my 12' Lowe starts to get close to planing speed, the motor falls on its face, and occasionally stalls. It will re-start. After this happens, if you gradually open up the throttle and give it some choke, it will run normally at close to WOT.

I've noticed the primer ball on the fuel line goes soft when this happens. Low speed operation is great, it idles perfectly, and works great as a kicker on the back of my 20 footer.

Any ideas, or should I deep six it? From my experience and what I have seen on these posts, Tohatsu sure does build some worthless 4 strokes."

"That's why they dress the

"That's why they dress them as Mercs

Seriously, Tohatsu builds a decent engine. Unfortunately a single cylinder 4 stroke is not decent.

They run like crap at the best of times - that poor piston has to get the crankshaft around 720 degrees between power strokes (since every second rotation is exhaust).

It sounds like you are either developing a clog in the carb or the fuel pump diaphram is on it's way out (just a rough guess).

Don't scrap the motor yet. Maybe spend 100 bucks and take it in. Have the valves adjusted, change any filters and replace the plug.

Try some Seafoam (or similar) in the gas - even one of the automotive 4 stroke carb cleaner additives may help a bit.

The closer you can keep this to "perfectly tuned" the better it will run for you.

Alternately, if you are looking for a new one and need to stick with an EPA/CARB rated motor because of the area you boat in, move up to a twin cylinder model.

It don't matter much who you buy from... Tohatsu builds their own, plus Mercs under 30 horse and all the Nissans - Yamaha builds their own plus Sail, Parsuns and two other brands sold in S.America and Europe that I can't remember - Suzuki builds almost everything else (including the now discontinued Johnsons).

Honda still stands alone - and is the only builder I would consider for a lower horsepower 4 stroke motor - strike that, the only builder I would consider period if I was buying a 4 stroke..."

"Graham - thanks for the advic

"Graham - thanks for the advice. I think you are on to something with the fuel pump, as Mercury Marine currently does not have any in stock for ME6M 4ST's in the US. Estimated backorder until 7-10-08. I'll try to track down the Sea Foam in the meantime.

This motor has some of the WORST factory service parts support I have experienced with any product, much less a US based company. Can't wait to replace this ME6M 4ST boat anchor with a Honda someday."

"Dave, if you can find a Tohat

"Dave, if you can find a Tohatsu dealer maybe they can help you out. I don't know how prolific Tohatsu is in the US yet, up here in Canada they are very few and far between.

But they did build your motor afterall, and Merc will be getting parts from them (on a wholesale level). Alternately, if no Tohatsu, if you can find a Nissan dealer, the 6 horse Nissan/Merc/Tohatsu 4 strokes are all "exactly" the same motor..."