Strange outboard problem

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ReggieK

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Anyone had a similar problem?
Have a Honda 5HP 4 stroke which started losing power. Brought to mechanic who adjusted throttle. Put motor back on boat, same problem, this time also cutting out. Took cover off & it ran perfectly. Brought back to mechanic who poo pooed idea that it would run without coverand not with cover, we ran it in his test tank with cover on and ran no problem. Back to boat, ran first time out then started losing speed and cutting out, take off cover runs perfectly. Nothing touching inside cover. No airways blocked. Help! anyone any ideas?
 
Perhaps its running on the rich side, and the air when warm is just tilting the ballance between rich, and too rich, and cover off allowing just that extra bit of fresh air.
Also check the crankcase breather is connected at the rocker cover incase it is drawing in crankcase gasses, through carb.
Can you let us know exactly what was wrong when you do eventually get the problem sorted, so we will be more wiser the next time.
Oh, one more thing, check the fuel filler cap vent incase it is blocked, you could remove the filler cap, or loosen it the next time it happens instead of taking off cover, to see if it runs, then you would know its not the cover, but the filler cap vent thats at fault.
 
Separate fuel tank, so it's not filler cap. When you say too rich would this indicate the choke may be the problem?
To a layman like me it's as though there is a lack of oxygen. However, the actual cover has no airholes at all, so taking it off shouldn't really make a difference. On Saturday, reversing out of marina as soon as I put it into reverse it started to cut out and lost power, frantically took off cover and it immediately recovered and ran perfectly. Branch of tree & thrashing to within an inch of it's life is next option!
 
This may sound barmy. Is it anything to do with the fuel line? I had terrible trouble on the same motor with the fuel line not supplying the motor properly. It was down to a pattern part (non-Honda) that had been fitted and the 'O' ring was distorting.
I just wonder if in removing the cover you inadvertantly move the fuel pipe and restore the flow.
The test is to push the connector hard on and hold it when you are having the problems. I had to travel for a couple of miles like that once until I could moor up and check it out.
 
This worrys me.

Ive been advised to buy a 4 stroke!

My Evinrude seagull and Mariner are oldish to old/very old but all work first pull (once in service) have never ever stopped once running (unless the fuel ran out)

Ive seen almost no posts about bad 2 strokes but LOTS for 4 stroke problems??Is it really worth buying a 4 stroke they cost more than a set of new sails!And i can almost aford those!

Would you buy new sails or a 4 stroke to replace an absolutly reliable 2 stroke?
 
Is your outboard fitted in a well? Sounds like ingestion of exhaust gases to me which would not be the case if running in a test tank or with cover removed. Perhaps well ventilation has become a problem.
 
mmm ... I'll be interested to hear suggestions on this one as have the same engine and had similar problems: backfiring then stalling, can feel loss of power beforehand, won't restart until cover removed then starts first time. Engine was new 12 months ago.
 
I don't think it's the fuel line, because it is running perfectly w/out cover and I don't think the fuel line gets touched.
HT lead may be a possibility I'll try on Saturday depressing it & see what happens.
Outboard is not in a well but mounted on stern, so thats not the problem.
Have had no problems before this, serviced every year now 4 years old and not big usage only leaving & returning to marina. Don't let me put anybody off 4 strokes!
 
Is the air vent in the filler cap blocked? When you take the cover off do you remove the filler cap? It will run for a short time with the blockage but when you run it on the boat for a longer period it stops due to fuel starvation.
 
[ QUOTE ]
Would you buy new sails or a 4 stroke to replace an absolutly reliable 2 stroke?



[/ QUOTE ]
I cant see any point in replacing a perfectly reliable outboard

.If I were you I would buy the sails now and start saving for a new outboard for when your old one finally packs up. It could go on for another 10 years or 10 days impossible to say .
 
I have had this problem on a yamaha 6hp 2s. It turned out to be a leaking gasket at the power head base allowing exhaust gases back in to engine bay. It was a small leak, barely detectable.
 
[ QUOTE ]
a leaking gasket at the power head base

[/ QUOTE ] I've heard of that happening before so it a good thing to look at.
 
If its difficult to see I wonder if with the engine running spraying gas fitters leak detector around the gaskets would show up any leaks?
 
Seen exact same problem with a friend who had the same model of engine.

It turned out that cooling water corrosion had opened a hole in the power head casting. From memory, looking at it from the cylinder head end, the hole was low down on the right of centre. The hole was letting exhaust gases out and when you put the lid on the engine choked on its own emissions.
 
I also had an engine with a water leak from a pipe union that filled the casing up with water when running (doh!) but of course when you came to strup it down it was all gone. If it is at all wet inside might be a clue, but the exhaust gas thing sounds feasable too. Don't run too well on carbon dioxide......
 
Many thanks for all the ideas
Sailing day Saturday will have a look then and see if any of these ideas bear fruit before going out into blue yonder.
It looks, however, that it will have to go back to friendly mechanic. Rupture time again lifting it off the stern!
Will keep you posted
 
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