1998 Mercruiser 4.3 Tick/Knock

[Ziggy12]

Hello, I have a what I was told was a 98 4.3L mercruiser.
I got the boat and it had a fuel problem. I fixed the fuel problem and it ran great for 1 day. At the end of the day, heard a metallic clicking / tapping/grinding type noise, boat slowly lost power and turned off. Tried to restart it but the starter would just grind on the flywheel.
I’ve replaced the starter and got it started but now it is making these awful noises and I’m just looking for some insight on where to look/ possible causes and fixes. Thank you

 

[Willyclay]

Welcome to the forum! The members here are great and should be able to help you fix your problem. I will just tag-along and try to identify anything that might help my son with his 1995, 4.3L Mercruiser I/O. Good luck!

 

[nola mike]

So hard to diagnose sounds over the internet
First, have you done any maintenance on the boat? Oil change, gear oil, pull the drive, etc? If saltwater, manifolds/risers been changed?
What was the fuel problem?
Slowing down/stopping, turning off--any overheats?
Also sounds like you might have hydrolocked it, but many other possibilities. Can you tell where the sound is coming from? Outdrive, head, block?
Here's how I'd proceed based on answers to the above, not necessarily in this order:
1. Change oil/gear oil, look for metal
2. Pull drive, start, see if noise persists
3. Pull plugs, check compression, note condition of plugs
4. Pull valve covers, look for something obvious
5. Turn engine by hand, see if it turns smoothly or binds at a certain point.

 

[Ziggy12]

So hard to diagnose sounds over the internet
First, have you done any maintenance on the boat? Oil change, gear oil, pull the drive, etc? If saltwater, manifolds/risers been changed?
What was the fuel problem?
Slowing down/stopping, turning off--any overheats?
Also sounds like you might have hydrolocked it, but many other possibilities. Can you tell where the sound is coming from? Outdrive, head, block?
Here's how I'd proceed based on answers to the above, not necessarily in this order:
1. Change oil/gear oil, look for metal
2. Pull drive, start, see if noise persists
3. Pull plugs, check compression, note condition of plugs
4. Pull valve covers, look for something obvious
5. Turn engine by hand, see if it turns smoothly or binds at a certain point.

Pickup screen in tank was clogged.
I checked the oil and it looked clean before I took it out.
Before this noise, compression was at 140 on all 6 cylinders.
I will be taking the drive off next.
I pulled one valve cover, only one of the valves/rockers.
It sounds like the sound is coming from the middle of the engine.

 

[rolmops]

You should get a mechanics stethoscope. It will help very much in localizing the place where the noise comes from. You can get them for less than $10 at your local car parts store