Problem with Honda 5hp Outboard Engine

dlf

dlf

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I am wondering if the mechanically minded amongst you could possibly offer some advice on the problem I am having with my Honda 5hp outboard engine (4 stroke). I purchased the engine from new 7 years ago and generally I don’t have any problems except when I run it for extended periods (approximately one hour or more). For some unknown reason the revs will suddenly drop off very quickly and then it just stalls. I am able to restart it but within twenty minutes or so the engine will stall in exactly the same manner. I have found that if I reduce the revs, it will run a bit longer but eventually it will stall. The longer I try to run the engine, the shorter the periods become between each stall and restart, until you get to a point where the engine barely runs at all. The oil is ok & the water cooling system seems to be operating fine. As I said early I don't have any problems during shorter running periods. Can anyone help or offer some advice?
 
Sounds like overheating slowly, then reaching seizure point! Perhaps blocked waterways. Hondas are prone to this, at the service each year does you service centre dismantle the leg and water pipes to ensure all the gunge that accumulates has been flushed?
 
i have experienced similar problems with mine with extended running ( 1999 model ). i have heard that these engines can develop a hairline crack in the exhaust manifold which leaks exhaust gas into the area under the cover and eventually deprives the engine of oxygen. i have certainly found that taking the cover off when it stalls seems to prevent the problem recurring.
it just seems to happen on fine days when you are running at max revs.
 
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i have heard that these engines can develop a hairline crack in the exhaust manifold which leaks exhaust gas into the area under the cover and eventually deprives the engine of oxygen. i have certainly found that taking the cover off when it stalls seems to prevent the problem recurring.

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I have seen this on a friend's boat except that it was a corrosion issue not a hairline crack. It leaving the cover off stops the problem recurring you are in the early stages of this problem.
 
This sounds a bit more ominous. I will experiment with the cover off to see if this helps. Are there any signs of the cracking externally or do I have to dismantle the engine to identify this as the cause?
Regards
 
Thanks for your reply. I will look into this and speak to my dealer to see if this is the cause of my problem.
Regards
 
It will be corrosion. The iboats forum in the US has many references to it. It seems to effect the BF75 even more. Some popel suggest liquid metal reapirs. One guy even fills the shround on his motor with water and as the leak is blow the water he reckons it runs until the water leaks out ??
iboats - Honda exhaust leaks
 
Do you think this problem would be economic to repair, or am I better off just buying a new engine?
 
I had a Honda 5hp. I bought a Yamaha.

That was to do with other reliability issues. Don't know what the exhaust manifold costs. Shouldn't be difficult to fix.
I have a Honda w/shop manual going cheap /forums/images/graemlins/wink.gif
 
I have a workshop manual on disc, but thanks for the offer. How do you rate the Yamaha compared with the Honda. I was thinking of buying 4hp Yamaha as a replacement to the Honda, if the Honda becomes too troublesome and expensive.
 
Run the engine without the cover, I think you will find it will run perfectly. If so, it is corrosion and exhaust gases are smothering it, to which these engines are particularly prone. Replace exhaust manifold or do what I did and bin the thing and buy a decent outboard.
 
Yamaha was great. Quieter. Less vibration. Tickover better. Absloutely reliable. Internal and external fuel supplies. Although only 4hp seemed to have more grunt than the Honda.
The only thing I disliked was the short gearchange lever, but modified it, which improved it no end.


Outboardgearlever2.jpg
 
Fuel cap vent is fine, but thanks for the suggestion. I did once forget to open the fuel cap vent fully and the engine stalled, but this happens very shortly after starting the engine.
Regards
 
Thanks for the recommendation on the Yamaha. I think you have persuaded me to take the plunge and get a new 4hp Yamaha. It was always my favoured option on paper but the owners feedback is very welcome.
I like the gear change solution!
Regards
 
imho the problem is clear and typical in all kinds of old petrol engines: high voltage system needs renewal. replace coil and cables first, then if problem continues electronic ignition. ask the cost of those( 99 % problem is coil) and think the difference of cost between this and trade in for a new one
 
Duh.
That will lead to enormous expense and no result.
If you read through the thread and follow some links you'll see that small Honda outboards suffer from corroded exhaust elbows.

There is no substitute for diagnosing a problem correctly. Scattergun approaches waste money.
 
I had exactly the same problem with my Honda BF15 on an Inland cruiser I had on the Thames.
Thought fuel starvation etc etc etc. The engine was serviced before the start of the season by an outboard specialist and towards the end of the season it would mysteriously lose power then cut out. like yours it would restart straight away, and if you were quick enough when it started to die, i'd drop the revs off quickly and it would just about idle without cutting out. All that the engineer did was change the spark plugs and it was working fine again. Now I know 2 strokes get the spark plugs quickly but not a 4 stroke engine. But this seemed to be the only way to keep the problem at bay. Change plugs very regulary!!
 
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