Vapor Lock?

[sybaris2]

I have a '05 Crownline with a 260hp 5.0 MPI Mercruiser. Ran fine end of last season. Got her out, checked all fluids, new gas etc.. started her up first try, sat dockside until temp got up to normal and shut her down. Took her out for an idle cruise about an hour later. About 15 minutes in engine started knocking and then died, wouldn't start, paddled home. This morning she started right up but I shut her down right after.

Any ideas as to problem/things to check much appreciated.

 

[achris]

Fuel tap was off? Air leak in the 'suck' side of the fuel system? Fuel pump relay failing? Fuel pump pressure regulator failed? Something else not right with the electrical that the ECU doesn't like? Take your pick.

 

[alldodge]

Any knocking on restart this morning

 

[Scott Danforth]

knocking is usually lack of oil pressure which is usually not a good sign.

 

[sybaris2]

Any knocking on restart this morning

No knocking. She's on a lift so she ran for only a couple seconds. This evening I'll set her in the water and let her idle until she gets up to temp.

 

[sybaris2]

knocking is usually lack of oil pressure which is usually not a good sign.

Oil pressure was fine dockside idle and idle cruising but when the knocking started I noticed the pressure start to dip but wouldn't that just be in relation to decreased RPM? Also the knocking sounded more like the sound a car makes when it keeps running after you've turned it off which is usually associated with heat. Temp guage was normal but then guages are not the most reliable indicators........... one other thing I noticed was when I went to turn off the batteries and opened the access it seemed very hot, even when I put my hand down on the lip of the opening it seemed unusually hot.

 

[sybaris2]

One more thing. I just checked the Water Distribution Housing. On this engine it's the lowest drain point. When I winterize I open it to let the water out then crank the engine over several times to ensure all the water is out of the lines. Then I secure it and fill the lines with antifreeze. When I opened the WDH antifreeze came out which tells me that there's been no exchange and the antifreeze kept the engine cool for a while until there was vapor lock?????

 

[Scott Danforth]

Also the knocking sounded more like the sound a car makes when it keeps running after you've turned it off which is usually associated with heat.

that is run-on. and that little gasp at the end is the motor running backwards and sucking water from your exhaust. I bet you hydrolocked which is why it wouldnt start til morning, I bet you find water in your oil

 

[Fun Times]

In reading these situations it would also seem as you may have unknowingly cranked the engine over several times over the course of the year while the boat is lifted out of the water and in possibly doing that has heightened the concern of compromising the rubber sea water inlet “Impeller” possibly helping to add too the hotter than usual feeling, knocking sounds, vapor lock symptoms, antifreeze left in the engine, etc. because the impeller may not have been receiving proper amount of water or mixing with air slowly cavitating the impeller and housing to where the water is not pumping properly now.

Is your stern drive an Alpha drive or a Bravo drive or other type? As that may help determine where your impeller is located for inspection plus replacement while checking all things over for the situation at hand.

 

[sybaris2]

In reading these situations it would also seem as you may have unknowingly cranked the engine over several times over the course of the year while the boat is lifted out of the water and in possibly doing that has heightened the concern of compromising the rubber sea water inlet “Impeller” possibly helping to add too the hotter than usual feeling, knocking sounds, vapor lock symptoms, antifreeze left in the engine, etc. because the impeller may not have been receiving proper amount of water or mixing with air slowly cavitating the impeller and housing to where the water is not pumping properly now.

Is your stern drive an Alpha drive or a Bravo drive or other type? As that may help determine where your impeller is located for inspection plus replacement while checking all things over for the situation at hand.

I only cranked it over once for a few seconds in the fall.
I just got back from setting her in the water and opened the water distribution housing to let out what was left then started it up. Nothing came out. I have a B3. I have read where folks change impellers every year. My boat is an '05 and it's never been done. Ordered an impeller.

 

[alldodge]

My boat is an '05 and it's never been done. Ordered an impeller.

Every 2 to 3 years is best

 

[sybaris2]

Replaced impeller. It was pretty chewed up. There were pieces in the impeller housing. Good strong flow now out of the water distribution housing. I hope the other pieces just got/get expelled through the exhaust.

 

[Fun Times]

In some to usual case's if it continuous to get a bit on the hotter side of what you know is normal under load then they are causing a blockage issue in the cooling system… I know you know that, just figured it might be Re-worth mentioning it while in here to say I hope the impeller was your main issue and all turns out good for you… Good luck.

 

[sybaris2]

In some to usual case's if it continuous to get a bit on the hotter side of what you know is normal under load then they are causing a blockage issue in the cooling system… I know you know that, just figured it might be Re-worth mentioning it while in here to say I hope the impeller was your main issue and all turns out good for you… Good luck.

Funny you should mention that. When I had the problem last week and opened the access to shut off the batteries man she was hot but the temp guage showed around 180. Yesterday took her out for a test run. Ran fine idle and fast. When I went to turn the batteries off after coming in she was noticably much cooler and temp guage was still around 180 so yeah gonna put a IR sensor on her to get some accurate readings. That said, I was able to reconstruct most of the old impeller with the pieces I recovered with the exception of 3 impeller fins that were half intact. So I'm wondering if there is a diagram that shows expected temps at various locations. I'm thinking if there was a partial blockage something like that might help to locate it.

 

[alldodge]

Easy test for overheat problem is get a piece of clear hose, double barbed fitting and hose clamps from HW store. Disconnect hose going into the Tstate housing coming from the pump. With boat in the water look for bubbles.

 

[sybaris2]

Problem solved. A travelling mechanic came and scoped the line after the impeller and found the missing impeller pieces. They were restricting flow. Runs fine now.