add y pipe flappers and/or increase exhaust manifold thickness by double the gaskets. Your manifold or head may not be perfectly flat. However, I suspect Y pipe shutters (flappers) will reduce cold water entering an exhaust system.
Sorry to disappoint you - Searay Sundancer has a muffler in the middle so there can not be hydrolock from water getting in from exhaust. Exhaust pipes are on the side of the boat hence sudden stop will not get the water in. I am not sure how other boats are done, but this IS NOT the issue here. No repetitive comments required from you on the same topic
Thank you for your support!
this one had us all stumped... one thing maybe that wasn't looked at is if the igntion timing was late/retarded temps can get hot especially exhaust gas.So! 3 trips made and it seems to be fine now.
What was done and what fixed it - I have no F***ing clue
New valve springs, heads done, all new gaskets, left and right side heads were swapped, new manifold. Engine is running better and not so big difference between port and stb engine anymore on power of consumtion on idle or under 3800rpm. I do hope that all is good now and this summer my main concern is petrol price
It was checked as well - and was OK. Consensus here seems to be linked to dead valve springs - during 3000 rpm excaust valve stayed mostly open and overheated that one spot, when cooling down with sea water, it made it crack
Well, we did check the compression on cold engine and all was good, also no major visible burns, however it was always flooded when heads came off...Pleased for you @mart284
I suppose a dead valve spring could lead to localised overheating around that exhaust port, this (valve float) could also account for this engine being down on power at 3000rpm compared to the other engine. Still I'm a bit surprised there'd be enough extra heat to cause the marine exhaust to crack.
But might expect the valve to get burned and compression to be down on the effected cylinder which would be a pointer to a head problem?
