[Gary Firth (Gazza) Posts: 3117 Status: Offline hovernerd WWW]

Still not an issue.

[Warby Posts: 1043 Status: Offline]

The main issue with inverted 503 engines is if they are left for a long time any oil left over from the fuel will drain from the crankcase and accumulate around the spark plugs! So for a Hovercraft that is left standing for a long time (as many are) the best bet would be to replace the plugs with an old set until it next used. (IMHO) !![size=78%] [/size]

[Gary Firth (Gazza) Posts: 3117 Status: Offline hovernerd WWW]

Inverted total not an issue.

[Warby Posts: 1043 Status: Offline]

More info
http://forums.bmaa.org/archive/index.php/t-1946.html

[Warby Posts: 1043 Status: Offline]

"its an inverted aircraft version fitted,"
[/size]There is a possibility that the starting problem and cutting out on idle could be attributed to the engine being inverted.[/color]
[/size]Many years ago I was looking at a similar problem on a friends outboard motor. It was a two stroke British Anzani, ( anyone old enough to remember them?)  and as mounted on the boat the cylinder head faced forward. So when the engine was tilted after use, any oil/fuel would collect around the spark plug and foul it making it difficult to start the next day. A simple cure was to tilt the engine and then turn it "full lock" to one side so the spark plug was not fouled!! [/color]
[/size]Note:- All other makes of outboard that I have seen have the cylinder heads facing to the rear so when tilted the spark plugs are " on top "[/color]

[A S T Posts: 18 Status: Offline]

Hi
    i would gladly change to a four stroke if funds permitted,its an inverted aircraft version fitted,some times hard to start,cuts out for no apparent reason when idling.Now a noise coming from engine or gearbox,not sure yet,between it wanting to sink by taking on water and now the engine problem.Happy days.!!!!!!

[rossfloyd Posts: 2025 Status: Offline]

Rotax 503 is very heavy on fuel if you use the power but a superb engine with excellent power/weight. The twin mag is the aircraft spec version and that really says it all ! Spares are eye watering however.

[Gary Firth (Gazza) Posts: 3117 Status: Offline hovernerd WWW]

Changing it’s a doddle
New gearing and blades engine mount. 

[Ian Brooks Posts: 3552 Status: Offline]

I changed one the other way, Kohler out and Rotax in. In fact, the one that Phillip had! But it was a meticulously maintained ex-microlight engine that I bought from someone I knew, so was all in good order. Started 2nd or 3rd pull reliably.

Perhaps go through all the usual service items? Spark plugs / air filter / clean and set up carbs etc?

It could be swapped for a 35hp Briggs but the cost would be enormous unless the engine were free, it would be new fan frame, fan, pulleys belt exhaust etcetera.

Ian

[Philip Posts: 2436 Status: Offline 12" above the Earth's surface WWW]

The Rotax should be a reliable unit, never had to do much to the one I had for a few years. What issues are you having?

[A S T Posts: 18 Status: Offline]

Hi
   Has any one changed the drive system on a Flyingfish as the Rotax 503 seems to be a pig of an engine.