Mercury/mariner/tohatsu 2 stroke aggro

[mogmog2]

Long shot but I know there are a good few of these around, so some pool of knowledge out there hopefully.
My little Mercury 2.2 was stored in our garage for nearly 20 years, so this is a low mileage engine. Last autumn I fettled the electrics & got it going & for the first few (1 mile there & back) trips it ran sweet as a nut.

Then it started playing up somewhat, dying slowly & sometimes restarting sometimes not. Latterly it would only run on high throttle. I stripped the carb & it started fine in the tank at home. Next trip out it cut out a few times on the outward trip & wouldn't start at all for the return. So I have again:

Critically inspected the fuel hose & connections.

Dragged a rag through the fuel hose to see if it's breaking up internally - it's not.

Stripped the carb down to component level & cleaned everything with carb cleaner. No obvious crud present at start.

Checked float for floatiness. Floats ok & doesn't leak.

Checked fuel delivery needle - shiny band but no obvious wear.

Checked the jets, run them through a bit with copper wire, then blown through compressed air.

Checked the various channels in the casting. One seems blocked and I have gently probed it & no crud comes out on the probe. (see photo) Maybe it bleeds very slowly? The channels in the casting suggest that it joins onto the other one which exits in the float chamber What is this hole for? Should it be clear?

Tank is clean

Fresh fuel

Spark plug clean & gap checked & is set for 40 thou.

Points cleaned and checked & set at 15 thou.

It started up easily & ran for 10 mins (with prop on, so some load), then stopped fairly abruptly. I think it was out of fuel though, as there was a bit in the tank, but it looks like there is a bit of pipe projecting above the tank base?

Refilled & now it's playing silly b's. I know 2 strokes can be a pain to start when they're warm, but it shouldn't be - that could just be the carb settings.

I got it started it ran for a minute or so then stopped fairly abruptly: coumd this indicate a fault in the HT coil? Can this be tested more thoroughly than checking for a spark at the plug? Either at home or by a pro? I have a multimeter and oscilloscope (but very new to the scope).

My questions are:
How to set up carb from strip down?
What is the hole in the photo for?
Can the HT coil be tested (how)?

I've got a lot of rowing ahead tomorrow afternoon if I can't resolve this
Many thanks.
.

 

[VicS]

Hole in carb top is I think just a vent

Points must be cleaner than a clean thing .. not even a finger print!

Check that you can get a good fat spark from the HT lead that will jump several mm

You should find carb adjust settings ( and float height setting) instructions in a service manual at http://162.144.28.33/

ITYWF that the "bit of pipe projecting above the tank base" is a filter. If you have not cleaned it it is very probably the cause of your troubles.
Check fuel flow to carb.

Tried a NEW plug ?

Inspect the condition of the exciter and HT coils. If either looks manky and you don't get a good spark then probably needs replacing.

If you have not already done so fit a new pump impeller. You dont want a 20 year old one to break up and block the cooling system

 

[lw395]

Buy it a newplug. It needs to know you care.
Is the plug wet or dry when it won't go?

 

[Bobc]

I would say, try a new spark plug and replace the float needle. They are the most common causes of problems with these engines.

 

[mogmog2]

VicS,
Thanks for all these.

Hole in carb top is I think just a vent

Points must be cleaner than a clean thing .. not even a finger print!

Check that you can get a good fat spark from the HT lead that will jump several mm

I've just tried checking the spark - not overly easy on your own. Have to say that what I saw wasn't a big fat spark

You should find carb adjust settings ( and float height setting) instructions in a service manual at http://162.144.28.33/

Thanks, that's brilliant! I've never managed to find anything like this yet.

ITYWF that the "bit of pipe projecting above the tank base" is a filter. If you have not cleaned it it is very probably the cause of your troubles.
Check fuel flow to carb.

I'll have a closer look at that. Fuel flows through the tap & hose pretty well I've got nothing to compare it with but it didn't look like the problem lies there.

Tried a NEW plug ?

Not yet. On my list. If I could buy one between Littlehampton & Emsworth, that would be great. Otherwise I'll order one.

Inspect the condition of the exciter and HT coils. If either looks manky and you don't get a good spark then probably needs replacing.

Exciter coil looks OK, the HT coil is so-so but encased, so hard to guage. The HT lead has seen better days but isn't what I'd call manky yet. I think it is sealed into the coil and I don't want to tug it too hard for that reason Do you know if there is a (machine-based) way of testing the HT coil? I believe the latter is hideously expensive if available & not cheap secondhand. I'm trying to rule everything else out before going down that route.

If you have not already done so fit a new pump impeller. You dont want a 20 year old one to break up and block the cooling system

I know I need to do this. It is on my list for when I get the thing running reliably. In the meantime, I inspected it & brutalised each vane & they survived with no signs of trauma, so they don't appear to be about to fall off. I can't get one in time and after this weekend I'll have time to mail order anything, as the boat will be on a pontoon rather than half a mile into Chichester Harbour.

 

[CalicoJack]

40 thou sounds a lot, might be worth trying 30 thou.

 

[RichardS]

Erratic symptoms like running at one revs but not another or starting one minute but not the next are usually down to fuelling in my experience, which means something still affecting the carb.

Electrical faults are usually more reproducible although not always so, so trying a new plug and points is usually a cheap option.

You can check the coil with a multimeter but if you can't find any ohm specs, you can really only check that the primary resistance is in single figure ohms and the secondary is about a 1000 times greater. Obviously a short circuit or open circuit is a dead give away .... but you won't have that.

Richard

 

[coenvanwyk]

I have a similar vintage 2hp Johnston Seahorse. My experience would be: try fresh fuel with the minimum amount of oil, these little motors are very sensitive to too much oil. Second, I second the new spark plug. We used to set it at the thickness of a box of matches' wooden side. Make that 1mm, and try.

Good luck!

 

[VicS]

40 thou sounds a lot, might be worth trying 30 thou.

But if you take the trouble to look at the manual in the link I gave you will find that it is the specified gap!

 

[VicS]

I have a similar vintage 2hp Johnston Seahorse. My experience would be: try fresh fuel with the minimum amount of oil, these little motors are very sensitive to too much oil. Second, I second the new spark plug. We used to set it at the thickness of a box of matches' wooden side. Make that 1mm, and try.

Good luck!

1mm ( 0.040") is correct for the engine.
OMC reduced their recommended gaps from 0.040" to 0.030" pretty much across the board some years ago although that may not apply to recent re-badged engines

 

[VicS]

VicS,
Thanks for all these.

I've just tried checking the spark - not overly easy on your own. Have to say that what I saw wasn't a big fat spark


Thanks, that's brilliant! I've never managed to find anything like this yet.


I'll have a closer look at that. Fuel flows through the tap & hose pretty well I've got nothing to compare it with but it didn't look like the problem lies there.

Not yet. On my list. If I could buy one between Littlehampton & Emsworth, that would be great. Otherwise I'll order one.


Exciter coil looks OK, the HT coil is so-so but encased, so hard to guage. The HT lead has seen better days but isn't what I'd call manky yet. I think it is sealed into the coil and I don't want to tug it too hard for that reason Do you know if there is a (machine-based) way of testing the HT coil? I believe the latter is hideously expensive if available & not cheap secondhand. I'm trying to rule everything else out before going down that route.


I know I need to do this. It is on my list for when I get the thing running reliably. In the meantime, I inspected it & brutalised each vane & they survived with no signs of trauma, so they don't appear to be about to fall off. I can't get one in time and after this weekend I'll have time to mail order anything, as the boat will be on a pontoon rather than half a mile into Chichester Harbour.

Force4 just off the A27 towards the Witterings

Seateach , now called Ocean Chandlery and located in Thornham marina

Emsworth Outboards in the Yacht harbour

 

[mogmog2]

Force4 just off the A27 towards the Witterings

Seateach , now called Ocean Chandlery and located in Thornham marina

Emsworth Outboards in the Yacht harbour

VicS,
Thanks, I don't know Emsworth way so well so either of those are good.
Might be all academic as I've dropped the float needle somewhere between my shed & my PC...

 

[thinwater]

You did not replace the fuel line couplers. They tend to develop vacuum leaks, leading to this sort of crankiness. You can test this by pumping the bulb hard when it gets cranky.

Also, these engines don't have a fuel filter; add an in-line lawn mower filter.

 

[VicS]

VicS,
Thanks, I don't know Emsworth way so well so either of those are good.
Might be all academic as I've dropped the float needle somewhere between my shed & my PC...

I regularly call into Force 4 on my way to the yard.

If I needed anything while I am there I have often gone to Seateach . (They used to be in North street before moving to by the Railway station) but not used them since the name change and move to Thornham . ( will be very handy though as less than a stone's throw away)

I know nothing about Emsworth Outboards

The float needle should be available as a "part" .... at a price!


Not clear from you posts if your engine has a remote tank or just an integral tank. I assumed the latter but if it has a remote tank, as thinwater seems to think, then as he says suspect air in-leakage esp at at the fuel line connector. There will also be a fuel pump, which could be defective, if it has a remote tank.

 

[jwilson]

I don't think any 2.2 hp will have a remote tank. In-tank fine filter (bit sticking up inside tank) is a suspect item with those erratic symptoms. A new fuel tap comes with the filter - I fitted one last year to my 3.3 - had similar mostly ran but occasionally wouldn't problem. Could have cleaned the old filter but the tap body was very slightly cracked and leaking.

 

[Topcat47]

20 years is a long time to store an engine. Don't forget the vent in the petrol tank cap. The "plastic" pipes will harden in that time and the inside of the tank will attract what we used to call "varnish" that flakes off and blocks the tap.

 

[seaangler23]

Bad plugs can do weird and wonderful things, worth replacing,
May have a spare carb off a low hour engine but think I threw it outside so probably gubbed

 

[anoccasionalyachtsman]

My 2p. I gave mine a going over when I got it a year and a half ago. I can't for the life of me remember why but I bought a new piece of fuel hose, so I must have seen something happening to it.

 

[GrahamM376]

20 years is a long time to store an engine. Don't forget the vent in the petrol tank cap. The "plastic" pipes will harden in that time and the inside of the tank will attract what we used to call "varnish" that flakes off and blocks the tap.

It's not unknown for drive shaft/crankcase seals to harden as well, creating air leak into what should be a vacuum.

 

[mogmog2]

You did not replace the fuel line couplers. They tend to develop vacuum leaks, leading to this sort of crankiness. You can test this by pumping the bulb hard when it gets cranky.

Also, these engines don't have a fuel filter; add an in-line lawn mower filter.

Thinwater,
I've got an inline mower filter on its way. There are no bulbs - the tap has a very shor hose-ish connection to the fuel tap, then about 8" 6mm ID hose to the carb. I pressurised this a bit & am reasonably satisfied that it is sound.