Engine clunk on first start

[Cbs57]

1996 sea ray with 5.7 mercruiser. Engine clunks then starts after starting it runs fine . If restarted after first start it starts back up with no clunk or noise. Any idea what is the cause ?

 

[Scott06]

1996 sea ray with 5.7 mercruiser. Engine clunks then starts after starting it runs fine . If restarted after first start it starts back up with no clunk or noise. Any idea what is the cause ?

Might be hydrolock maybe water getting in cylinders from leaking exhaust manifolds ? First hit of starter expels water then yiu are good till its sits off long enough to drip water in cylinders.
are spark plugs clean ? Water in combustion chamber will clean carbon off plugs and chamber. You can test this theory by letting it sit, pull the plugs out , spin it over water will come out plug holes

 

[Lou C]

Yep, agreed with possible hydrolock, check that first and then make sure the starter bolts are tight.

 

[Scott Danforth]

High probably of hydrolock.

Pull the plugs next time and find which cylinder is spitting water

 

[jimmbo]

Hydrolock means unable to complete the compression stroke, so how would it start and run?

 

[Cbs57]

Might be hydrolock maybe water getting in cylinders from leaking exhaust manifolds ? First hit of starter expels water then yiu are good till its sits off long enough to drip water in cylinders.
are spark plugs clean ? Water in combustion chamber will clean carbon off plugs and chamber. You can test this theory by letting it sit, pull the plugs out , spin it over water will come out plug holes

Thats what I was thinking , I'll check the plugs and spin it over this weekend . will call our local sea ray dealer and order the manifolds.

 

[Scott06]

Thats what I was thinking , I'll check the plugs and spin it over this weekend . will call our local sea ray dealer and order the manifolds.

See if thats the issue first. Is this a fresh or saltwater boat? You dont need to get manifolds from a sea ray dealer , you can get merc or Barr manifolds lots of places. Would at least compare pricing. For refernce you can find an oem merc kit with manifolds and elbows gaskets and hardware for $955+ sh, Barr for about $855+ sh.
if yiu do find water in there also check oil for water intrusion. If present be prepared to do a couple oil changes to clean it up.

 

[stresspoint]

a couple of other things to look into > serpentine belt tensioner sticking . gimble bearing locking drive IE ; first start with trim in trailer position..

 

[tank1949]

1996 sea ray with 5.7 mercruiser. Engine clunks then starts after starting it runs fine . If restarted after first start it starts back up with no clunk or noise. Any idea what is the cause ?

Define "Clunks" better! Maybe Bendix? Old boat! Pray it is not flywheel ring gear going bad. Been there! Fore peace of mind, pull plugs and see if any rust.