1989 351W Engine Knock

Message Topic Search Topic Options Post Reply Create New Topic Printable Version Translate Topic

Hi Guys,

Its been a long time, but my engine/boat problems aren't over 

My previous thread where I replaced the engine is here:

https://www.correctcraftfan.com/forum/forum_posts.asp?TID=51037&PN=3&title=1989-sn-water-in-oil-wet-plug

Since fitting the "new/used" engine and getting it running last year, I only used the boat for 3 days and everything was great.

Then
 a week later (still in December 2023) the boat was running great, but 
then while cruising for about 10 minutes at ~2500 rpm I heard a knocking
 sound.

It was a deep knocking sound, at a rate
 of about 2 knocks per second. I slowed the boat down, and it idled 
fine, and the knock slowed down to about 1 knock per second. I sounded 
like it was coming from the back of the engine (transmission side) but 
it is hard to be sure as the cover was closed.

I
 shut the boat down, but couldn't see anything wrong. I tried to 
restart, but it puffed and spluttered and would not start. So I towed 
the boat in. I am not sure if the starting problem is directly related 
or maybe it was totally heat soaked?

I have been so busy this year that I haven't had much time to diagnose.
- Plugs look fine
- Oil looks good - no metal shavings

I have pulled all the plugs, disconnect ignition and raw water pump, and cranked the engine. It turns over smoothly, no noises.

I then did a compression test, and all cylinders were around 140 psi, but what was strange is than during the compression test of cylinder 4, it made a puffing sound (almost like a backfire) at the intake area. None of the other cylinders did that.

Any suggestions or ideas?

Thanks,
Greg

Author	Message Topic Search Topic Options Post Reply Create New Topic Printable Version Translate Topic
Greg_SA Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: April-19-2007 Location: South Africa Status: Online Points: 173	Post Options Post Reply Quote Greg_SA Report Post Thanks(0) Quote Reply Topic: 1989 351W Engine Knock Posted: September-14-2024 at 6:44am
	Hi Guys, Its been a long time, but my engine/boat problems aren't over My previous thread where I replaced the engine is here: https://www.correctcraftfan.com/forum/forum_posts.asp?TID=51037&PN=3&title=1989-sn-water-in-oil-wet-plug Since fitting the "new/used" engine and getting it running last year, I only used the boat for 3 days and everything was great. Then a week later (still in December 2023) the boat was running great, but then while cruising for about 10 minutes at ~2500 rpm I heard a knocking sound. It was a deep knocking sound, at a rate of about 2 knocks per second. I slowed the boat down, and it idled fine, and the knock slowed down to about 1 knock per second. I sounded like it was coming from the back of the engine (transmission side) but it is hard to be sure as the cover was closed. I shut the boat down, but couldn't see anything wrong. I tried to restart, but it puffed and spluttered and would not start. So I towed the boat in. I am not sure if the starting problem is directly related or maybe it was totally heat soaked? I have been so busy this year that I haven't had much time to diagnose. - Plugs look fine - Oil looks good - no metal shavings I have pulled all the plugs, disconnect ignition and raw water pump, and cranked the engine. It turns over smoothly, no noises. I then did a compression test, and all cylinders were around 140 psi, but what was strange is than during the compression test of cylinder 4, it made a puffing sound (almost like a backfire) at the intake area. None of the other cylinders did that. Any suggestions or ideas? Thanks, Greg
	1989 Ski Nautique (SN2001)

KENO Members Profile Send Private Message Find Members Posts Add to Buddy List Grand Poobah Joined: June-06-2004 Location: United States Status: Offline Points: 11032	Post Options Post Reply Quote KENO Report Post Thanks(0) Quote Reply Posted: September-14-2024 at 7:15pm
	it's coming from the rear, #4 cylinder is in the rear and it did funny things. As a starting point, maybe pull the valve cover off and look at the rocker arms and springs for #4 especially the intake because of your description.

Fl Inboards Members Profile Send Private Message Find Members Posts Visit Members Homepage Add to Buddy List Grand Poobah Joined: January-20-2008 Location: United States Status: Offline Points: 2092	Post Options Post Reply Quote Fl Inboards Report Post Thanks(0) Quote Reply Posted: September-15-2024 at 3:37am
	leak down test on number 4. and maybe the rest. i had one do that a number of years ago. turned out exhaust valve stem retainer was not installed correctly and it dropped the valve on top of the piston.
	Hobby Boats can be expensive when the hobbyist is limited on their own skill and expertise. 1993 Shamrock "fat" 20. 2008 Nautique 196 5.0

Greg_SA Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: April-19-2007 Location: South Africa Status: Online Points: 173	Post Options Post Reply Quote Greg_SA Report Post Thanks(0) Quote Reply Posted: Today at 6:25am
	Managed to remove the valve cover, and this is what I found. No. 4 exhaust rocket bolt has sheared off. - Is it possible to pull the stud and replace without removing the head? - I believe the studs are press fit? - Could this have caused the knock sound? I would expect a tick not knock? I saw a video of someone that tapped the broken thread on the stud a bit longer and use a nut and washers to extract it. Fitting a new one would probably require a press? Or tap the hole and use a threaded stud to replace? I do have my previous engine's heads as spares, but it is a bit different (newer style with bolt down rocket gear). I assume mixing different heads is a bad idea? These are the spares I have.
	1989 Ski Nautique (SN2001)

KENO Members Profile Send Private Message Find Members Posts Add to Buddy List Grand Poobah Joined: June-06-2004 Location: United States Status: Offline Points: 11032	Post Options Post Reply Quote KENO Report Post Thanks(0) Quote Reply Posted: Today at 1:18pm
	Like you're thinking, you can do it right in the boat with the head on. I'd probably either thread it like you said or weld/get somebody to weld a threaded piece to it. Kinda a tough spot to use a die, so if you weld a 1 1/2 inch or so piece of threaded rod you can pull it easier using techniques you probably saw in those videos. I'd go for a threaded stud to replace it. I'd guess that the pushrod randomly banging up, down and all around made plenty of noise

Greg_SA Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: April-19-2007 Location: South Africa Status: Online Points: 173	Post Options Post Reply Quote Greg_SA Report Post Thanks(0) Quote Reply Posted: Today at 1:59pm
	Thanks I'll look into both option to remove the stud. Can I safely pull out the push rod, to check that it is not bent? Can removing the push rod disturb the cam followers below?
	1989 Ski Nautique (SN2001)

1989 351W Engine Knock

About CCF

Donate

Partners

Contact