Right, just realised that the trim tabs were not fully down and got the boat to plane and this increased revs to 4000rpm but still would not go any higher and the growling was deafening, can this increase in revs help with the trouble shooting, just the fuel pump and carbs left now to replace.....rather not the carbs (quite costly) <br /><br /><br />Running out of things to check now, complete ignition check and tune up completed, fuel system tested as far as the carbs, head serviced, exhaust checked. The only things left are the prop and carbs, although i have stripped and cleaned carbs could they still be causing the problem? i have not played with the mixture other than the base setting given in the manual, which i think was 1 1/4 turns from seat, also cannot see where i can fit a vacum guage on the inlet manifold? Oh and one thing i have noticed when i changed the plugs..they were as black as newgates knocker, i.e very sooty. <br /><br /><br />Have a 21ft cabin cruiser fitted with a Volvo 130d which will not go above 3000 revs, have changed points, dist cap, rotor, plugs & leads, engine revs fine out of gear but growls at 3000 revs, any help appreciated.
<br />I will learn........<br />As for filters there is not a water seperater fitted, i checked the filter in the little finger operated pump located under the raw water filter, also the screen filters in the carbs. However Could you help me out with this "Check vacuum, fuel pressure anti-siphon etc"<br />I cannot see any kind of vacum pipes anywhere, also how would i check the fuel pressure.<br /><br />Many Thanks