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MitchM · 13-11-2010, 08:08

if you are lucky, you just fried the innards of your exhaust hose and impeller. you are lucky your mechanic caught the collapsed hoses. i have seen situations where the inner wall of the hose partially collapses only at high temperatures. what's happened is that the high heat has delaminated the walls of the hose from each other . the hose seems to be fine at idle but collapses at high rpms . can happen to raw water inlet hoses if the water pump supply hose is close to your overhot engine block. this one is a devil to sort out.so to be safe, i'd also replace the hoses that were closest to your hot engine block: ie the ones feeding into the front of your heat exchanger and possibly the hoses into /out of your raw water pump. did you say th boat is 30 yrs old? it's likely the hoses are too. to save some mechanic $$$, you can replace some of those hoses yourself....
it may be time for a valve job .setting the clearances of the inlet/exhaust valves can be done by your mechanic with the boat in its slip. if necessary he could also replace the head gasket and retorque the head bolts. knowing mercedes heavy duty construction, it's possible that's all your engine will need. and those are eventual regular maintenance items any way...

three ideas for you:
(1) put a rope loop on your engine start key. drape your engine start key on top of your raw water inlet seacock handle when you close the raw water seacock after a sail.. so next time , you cannot start your boat engine without remembering to open your seacock...

(2) there is an aftermarket band- style exhaust alarm made by borel. it is reasonably priced and sounds a shrill alarm to wake the dead when your engine temperature gets higher than about 200 degrees. the alarm is very reasoanbly priced about $80 or so as i recall. it is a self install and the only size you need to know is the circumference of the exhaust hose. i have a temperature gauge and audible temp sending unit on the engine block, but i added the borel as a safety backup. costs less than 1 hour of mechanic time....

(3) don't be upset about forgetting to open the raw water inlet. most everyone does that sometime. just make it a beginning lesson in your upcoming wonderful years of boat ownership.

and NEVER crank your engine repeatedly (ie more than 30 seconds cumulative) with the r w seacock open, as your faithful r w pump will eventually fill up your exhaust with water, which could back in thru your valves and do horrible things to your piston crowns...

crazyhorse77 · 14-11-2010, 11:58

Thanks Mitch for you ideas, I will definally add a exhuast alarm!

Finished replacing all the exhaust system and had the mechnic over on the weekend for the first start to help me if it went wrong. Started and runs really well!

The mechanic (travis westwood from ipswich) was great and gave me loads of free advice, which was.

+ take out injectors and get them serviced
+ replace all fan belts
+ check value clearances and adjust

I am enjoying all this engine fixing, so much better doing it out at sea

Cheers

perchance · 02-01-2011, 15:47

You may have suffered a partial engine seize when it overheated. That may explain the screeching you heard. In this situation we cut the oil filter open and wash the paper element in solvent to check for metal particles. A magnet separates the ferrous from the non ferrous particles.

bigman1 · 10-01-2011, 16:23

No matter how much you crank your engine,it wont flood,if you fit an anti-siphon valve on the water injection hose,where it enters the exhaust pipe,the rubber hose should have a 12"min.loop with the valve at the top,and check the valve every now and then to check it has not salted up,if it has it will be useless until cleaned.every boat with an inboard engine should have one of those valves.ps the vented loop should be well above the water line at all angles of heel.

Sailmonkey · 13-01-2011, 12:03

Quote:

Originally Posted by bigman1

No matter how much you crank your engine,it wont flood,if you fit an anti-siphon valve on the water injection hose,where it enters the exhaust pipe,the rubber hose should have a 12"min.loop with the valve at the top,and check the valve every now and then to check it has not salted up,if it has it will be useless until cleaned.every boat with an inboard engine should have one of those valves.ps the vented loop should be well above the water line at all angles of heel.

Ummmmmmm...........no, the anti siphon won't prevent the muffler from filling up with water when not being discharged by exahust.........they're for a different matter entirely.