Mercruiser 165 6cyl inline dies when boat is in the water

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cyclops222

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Wife and me have budgets.
Boat has no limits to keep running and safe. :)
Nether of us can walk to shore.
 
Y

YOBE

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Scott06 said:
you picked the wrong hobby….

make sure the flapper didn’t break of and is down in the exhaust oath blocking it they can work their way down to the drive
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Oeps…. That’s a scenario i didnt think yet of.
When I removed the stern I installed a new exhaust rubber. Didn’t see anything abnormal then. But will see what I can find

I know about the costs but I’m just starting to doubt if The engine is worth it.😒
 
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YOBE

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Bought a simple borescope. Hopefully will learn me something more about inside of the cylinders.
 
C

cyclops222

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It can be use in other passages also. Like removing the thermostat and looking in as far as possible.
 
Scott06

Scott06

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YOBE said:
Oeps…. That’s a scenario i didnt think yet of.
When I removed the stern I installed a new exhaust rubber. Didn’t see anything abnormal then. But will see what I can find

I know about the costs but I’m just starting to doubt if The engine is worth it.😒
Click to expand...
Always the concern/choice/ decision With an older boat. Best thing if you like the boat repower with a more recent vintage tear out bobtail.

have same issue with our 2004 jetski, lots of hours been easy on wallet but it’s up there in years. This winter the seals on crankshaft that seal oil chamber for rotary intake valve shaft leaked enough 2 stroke into engine that it hydrolocked this spring…when not in use i put a clamp on the oil line , not worth pulling the engine to replace these seals
 
kd4pbs

kd4pbs

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The nice thing about an inline six is their smoothness. Anything else commonly available in a boat will vibrate more. That engine can be modified to make quite a few ponies if one so chooses.
 
Y

YOBE

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Hi,

No luck.... :-( Once boat is just in the water, not even putting it in gear, it dies...

Thanks for the advice that was given for this issue.
1. Checked wiring => all OK
2. Installed new points
3. Set gap both on 0.16 (ref manual) but also tried 0.20
4. Checked the dwell with my scope and looks good
5. Checked timing => Set to 6

But issue stays the same:
Out of the water engine runs idle and high revs.
Once in the water the back pressure kills the engine after it runs for a few seconds.

Not sure if this helps: but I always run the engine before I leave for the water.
Once in the water it takes a few minutes before it dies. Then when I start it again it clearly dies way faster.

Any suggestions for the next step to diagnose? Thanks up front.

Regards,

PS: removed the carb (again...) and will double check everything.
 
Bondo

Bondo

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Ayuh,..... Did you ever check to see whether the shutter has fallen into the down-pipe,..??
 
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YOBE

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Bondo said:
Ayuh,..... Did you ever check to see whether the shutter has fallen into the down-pipe,..??
Click to expand...
Not yet, is next on my to do. But im 95% sure its clear. Will double check.
Really struggling to understand the problem….
 
alldodge

alldodge

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Not keeping the same thread is also an issue with others trying to help.

The only thing different between a hose and in the water is back pressure on the exhaust. In most cases that's low compression
 
Y

YOBE

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alldodge said:
Not keeping the same thread is also an issue with others trying to help.

The only thing different between a hose and in the water is back pressure on the exhaust. In most cases that's low compression
Click to expand...
OK, sorry, will use the same thread. Wanted to avoid making it too long
 
Y

YOBE

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Update:

Full exhaust circuit is checked, no blockage found (flapper must have been removed while ago). So this is OK.

While I am waiting for the upper oil seal (stern drive-yoke) to arrive I double checked the carb again.
As I am not using the choke at all, here we only boat in summer time, I found out the there was a leakage on the vacuum port used for the choke baffle.
I closed that one now, but not sure if this is the root cause of my issue.

Hope to test again in a week or so.
 
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kenny nunez

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In post#4 you said that with an electric fuel pump the engine runs. Am I wrong the way I am interpreting that?
Have you ever tried by passing the tank by using an outboard tank directly to the fuel pump with the primer bulb? If your engine is running out of fuel you may have a crack in the suction tube in the tank.
 
Y

YOBE

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kenny nunez said:
In post#4 you said that with an electric fuel pump the engine runs. Am I wrong the way I am interpreting that?
Have you ever tried by passing the tank by using an outboard tank directly to the fuel pump with the primer bulb? If your engine is running out of fuel you may have a crack in the suction tube in the tank.
Click to expand...
Hi,
Must be a misunderstanding. The mechanical pump doesn’t work. So I installed an electric one.
The issue of the engine happens with the electric pump. But only when boat is in the water
 
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kenny nunez

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In that case try the 6 gallon outboard method. This is a tried and true way to locate fuel problems, or rule it out.
 
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