ok, have a 454 with a berkeley jg pump. new packing gland and transom sealed. at idle there are no leaks from pump or cooling lines. have a valve at inlet line and outlet, both are fully opened. problem at idle the motor heats up to redline but once going its fine. is this because there's not enough water circulating? and then when the water can get through the headers it flows more? other problem is when not at idle (usually above 3000 rpm) there is a leak coming from somewhere. and its a pretty good one. my guess was a hose or something leaking when theres more pressure but I can't find anything wrong. any help....its driving me crazy. nothing like letting off the throttle and have a river come down the center of the boat. thanks for anything ya got

have you checked the stuffing box maybe? either that or a cooling line somewhere is my newbie opinion.

Is this a new problem?

Do you know anything about the history of this engine?

Is it a mk4 or gen5 block? 

one more time...

Is this a new problem?

Do you know anything about the history of this engine?

Is it a mk4 or gen5 block? 

Is it possible, and just thinking out loud, that your O/B dump or line to it is clogged up or pinched off with something? Wasp nest, spider nest, Sand?

If it's fine when the header valve opens, the other dumps.........I dunno, was just a thought.

Ray

I have heard similar stories when you have Gen V heads on Mk IV block or visa versa.  Also if you have the wrong head gaskets or the head gaskets are put on wrong.  The steam holes are different on many heads and are easily confused.  Also check expansion (freeze) plugs and block drains.

my .02
p-jet