stacer

Many thanks everyone for your ideas, I remain fairly confident that it is not a fuel problem given the bleeding and changes of filters etc. The engine may be overheating but not enough to set off the alarm which may of course be linked to the airlock found in the skin tank adjacent to the cooling input pipe. I will be taking the boat out again in about 2 weeks time so I will see if this is correct or not. The blackened air filter element might be explained by the location of the exhaust outlet, immediately adjacent to the port side air intake. The new style beta air filter seals tightly against the filter housing and perhaps in locks might pull in exhaust gases? I'll keep everyone posted as this develops.

I have spoken to BETA and agreed for an engineer to visit if the problem persists, BETA to pay if it's an engine problem, me to pay if not. Belt dust should not be a problem with the poly fee belt and it was a like for like swap so the skin tank should be fine. Thanks everyone for your ideas, it all helps.

Fairly sure it's not fuel, no water or debris in the primary filter, all fuel filters changed. Also problem only occurs after 2-3 hours running, so more likely to be temperature related. Also there is the question of the air lock and raised water level in the expansion tank.

I had a new engine installed last June (Beta 20) and up until a couple of weeks ago it ran perfectly. One day after about 3 hours running, the engine suddenly ran unevenly at about 1400 rpm but opening or closing the throttle restored normal running. Each time the throttle was set to about 1400 rpm, the problem returned. Suspecting a fuel problem, the engine was serviced with all filters replaced, the only thing of note was some blackening of the air filter. The exhaust lagging was removed, no evidence of a leak was seen but all joints were externally sealed with high temperature silicone and the lagging replaced. After 3 hours running, the problem returned and any attempt at 1400 rpm resulted in uneven running. After a further 6 hours running, it was noted that the water level in the expansion tank had increased and the new air filter was once again becoming blackened on its outer surface. The next days cruise was about 6 hours during which the problem returned as before and when the engine was cooled, the water level in the expansion tank was overflowing when the cap was removed. RCR engineer attended and said the blackening on the air filter element was normal, bled the skin tank which let out a fairly large amount of and returned the water level to normal. His opinion was that the problem was caused by air in the system despite 200 trouble free hours since installation. Any ideas would be most welcome.