Is the outboard running too rich?

Golden Time

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Some of you may know that I recently had an engine problem that was narrowed down to the spark plugs.

In my search for replacement plugs I was in a (motorbike) shop and handed over the spark plug for them to look for one. The chap said that my engine was running too rich because of the colour of my plugs. He said they should be the colour of a rich tea biscuit not black.

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Is he right that the engine is running too rich? Should I try to make it a bit more lean or leave well alone? If it should be more lean how do I do it?

The outboard is a Honda 9.9 and I have no idea about service history, so they could have been super old plugs.
 

vas

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use the engine with the new plugs, tank, pipework etc for a while. Clock 5-10hrs. Then remove plugs and check, I bet they'll be looking fine, especially if you did mention in the previous thread that o/b is working fine with the new plugs and pulls nicely

my 0.02euro

V.
 

Lakesailor

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How long to you typically run the engine for. Until it has warmed up properly and been off choke and under load the plug will be a bit murky.
Like has been suggested. Put in a new plug and go for a bit of a motor about using at least half throttle. Then check the plug.

This is the sort of colour he means. (This plug was on the point of being thrown away. I don't use open throttle much and the fouling on the centre electrode starts to cause tracking and poor running. Running it for 15 minutes under load at a higher throttle opening would probably have burnt off most of the soot.)

Badplug2.jpg
 

Golden Time

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How long to you typically run the engine for. Until it has warmed up properly and been off choke and under load the plug will be a bit murky.
Like has been suggested. Put in a new plug and go for a bit of a motor about using at least half throttle. Then check the plug.

This is the sort of colour he means.

use the engine with the new plugs, tank, pipework etc for a while. Clock 5-10hrs. Then remove plugs and check, I bet they'll be looking fine, especially if you did mention in the previous thread that o/b is working fine with the new plugs and pulls nicely.

We normally run a mixture of short 30-50 minute runs (to the first or second pub) then the same back. Most of that run is at low throttle as I go past the residential moorings and its speed restricted to 3mph. If we go the other way then we typically run for 3-4 hours each way at about 90% throttle once we clear the Glory Hole, city centre and the lock. WOT makes for a boneshaking ride.

You've both confirmed what I thought I should do, run the new setup and reinspect after a couple of good runs.

Be warned, if you start fiddling with the mixture and lean it off too much, you can easily burn a hole in a piston. Unless you know what you're doing here, leave well alone or get someone who knows what they are doing to do it.

I defo don't know what I am doing when it comes to fiddling the mixture so I wouldnt be doing any DIY on it. But I was looking for a consensus on whether I should be looking for someone who does know what their doing and I'm getting the distinct feeling to leave it alone. LoL. If I learnt anything from my Nitro RC Monster Truck days, too rich is far better than even a smidgen too lean.

On a sort of separate note... when the engine is idling there is a drip of water spitting out the back every few seconds. When you choke the engine to warm it or apply throttle the water becomes a really fast drip but doesnt quite make a stream (if that makes sense). If it got any faster it would be a steady stream. Is this normal for this size engine? Most the boats I see on the move are inboards and for comparison Ive only ever seen a 50hp outboard that had almost a jet of water coming out the back at idle.

BTW, thanks for all the help with my constant questions.
 

Lakesailor

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This is my Tohatsu 5hp at tickover. Most of the cooling water goes down the leg in the exhaust. It's not a given that there will be a strong stream from the pee-hole. Some engines can suffer from a blockage in the outlet, some it seems to stay clear.

I don't think you can affect the running mixture without changing the jet. The only adjustment on these small motors is the tickover air bleed valve. Usually you screw it in and then back out by 1 1/2 turns (but check the handbook/manual)

motorstarboard.jpg
 
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PaulGooch

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If it's only adjustable by re-jetting, it probably won't need doing. It might need some cleaning though.

Used to race tune 2-stoke engines a few years back, mixture was very border line. Within reason, the leaner it was, the better it went, up to the point where it ate the top off the piston in seconds. If we ran them too close to the limit, a slight change in the weather and the mixture changed enough to make it too lean, bye bye another piston :eek:
 

Momac

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Where will I find the numbers that correlate to the numbers on the website so I know which manual to be reading for my engine? I've had a short sharp introduction to the engine, LoL.

I guess there will be an engine number stamped on the engine somewhere, or perhaps a label/sticker under the engine cover? I dont know anything specific about your engine type - just trying to help.

A few petrol boat issues seem to be related to gum that is left behind after pertol evaporates, when the engine is unused for a while.
Perhaps a squirt of carburettor cleaner will help - something like this http://www.halfords.com/webapp/wcs/...uctId_202903_langId_-1_categoryId_255221#tab1
 
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