Fear the worse, loud banging sound comingfrom the engine

[jasonmd13]

I have a 1996 18' Rinker bow rider with a 4.3 lx mercrusier inboard/board. Tonight it was running good. Yesterday, I changed the oil and tighten the alternator belt, and the fuel separator. It ran good all day. All of a sudden it started making a loud banging noise. It was okay idling, but sounded like it had glass packs in the motor compartment. It put it in neutral and reved it up and it still made the noise . After I turned it off, I had a hard time cranking it. I had to give it gas to crank. Any ideas? I haven't had any trouble with it. Thanks

 

[jasonmd13]

Re: Fear the worse, loud banging sound comingfrom the engine

It didn't run hot, had good oil pressur , and still pulled good.

 

[Bondo]

Re: Fear the worse, loud banging sound comingfrom the engine

It didn't run hot, had good oil pressur , and still pulled good.

Ayuh,... Do a compression test on it,...

 

[jasonmd13]

Re: Fear the worse, loud banging sound comingfrom the engine

Ayuh,... Do a compression test on it,...

What should the compression be? I have done one on a jet ski but not a boat. I'm scared it's a rod

 

[jasonmd13]

Re: Fear the worse, loud banging sound comingfrom the engine

This morning, I tried to ease it back, and all of a sudden it quieten down. Going to change pulls and see what happens, all gauges are good

 

[Watermann]

Re: Fear the worse, loud banging sound comingfrom the engine

You may have just over tightened the belt and hastened the death of the already weak alternator bearings.

 

[jasonmd13]

Re: Fear the worse, loud banging sound comingfrom the engine

You may have just over tightened the belt and hastened the death of the already weak alternator bearings.

Hopefully that's it. It was squealing when I took off fast, so I tighten it. This was the first trip since. But it was a loud popping sound. Almost like straight exhaust, whether in gear or not and the faster I went, the longer it got. This mornin , it just quieted down. Now just a ticking sound. But rpms seem down about 400 , running 4200 wot.

Would the alternator make such a popping sound?

 

[jasonmd13]

Re: Fear the worse, loud banging sound comingfrom the engine

Not the alternator, took the belt off and still ticks

 

[Watermann]

Re: Fear the worse, loud banging sound comingfrom the engine

If you can get a video of the motor running and making the noise.

 

[Bondo]

Re: Fear the worse, loud banging sound comingfrom the engine

What should the compression be? I have done one on a jet ski but not a boat. I'm scared it's a rod

Ayuh,.... Even numbers are more important than the number,...

100 psi is a rebuildable core motor,....

150 psi, 'n up is a healthy beast,...

 

[jasonmd13]

Re: Fear the worse, loud banging sound comingfrom the engine

Video of it idling. Sorry it was upside down. All the gauges look ok, temp, oil pressure, ect. but my take off is down, and I lost about 600 rpms. My wot is now 4200 instead of 4800.

 

[jasonmd13]

Re: Fear the worse, loud banging sound comingfrom the engine

This is a video of it in neutral and throttle up a little bit.

 

[jasonmd13]

Re: Fear the worse, loud banging sound comingfrom the engine

If you can get a video of the motor running and making the noise.

throttle up - YouTube

 

[jasonmd13]

Re: Fear the worse, loud banging sound comingfrom the engine

Could too much oil cause all this? Seems unlikely, but I seen someone say it could cause ticking. I changed the oil right before I went to the lake but seemed about a quart high in the water. I'll go check it again out of the water.

It's weird that the ticking in the video was ear popping and then went to a tick. I changed the pulled and checked the altermator. Wish I could find the problem

 

[jasonmd13]

Re: Fear the worse, loud banging sound comingfrom the engine

The oil was maybe a half a quart high. I drained it to a normal level, but still ticks. The ticking seems to be coming from the front of the motor.

 

[glenn property of pam]

Re: Fear the worse, loud banging sound comingfrom the engine

drain the oil in to a clean container then see if it has silver glitter in it. Im not a expert but that sounds like a rod knock.

 

[Mischief Managed]

Re: Fear the worse, loud banging sound comingfrom the engine

Take the belt off and start it for a bit to see if the noise goes away. I had a circulating water pump make loud rapping noises like that once.

 

[jtrasap]

Re: Fear the worse, loud banging sound comingfrom the engine

You say the oil was high: is it milky or does it smell like gas?

It does sound like a rod knock but sometimes sound from videos can be deceiving. Does the noise quiet down when you put the boat in gear? Often times a rod knock will quiet down a bit when under load and get louder when sitting in neutral. Also, when reving the engine in neutral a rod knock will often get much louder just after you let off the gas due to the load being taken off of the bearing.

 

[jasonmd13]

Re: Fear the worse, loud banging sound comingfrom the engine

Take the belt off and start it for a bit to see if the noise goes away. I had a circulating water pump make loud rapping noises like that once.

I'll try that, my mechanic thinks it might be a bad lifter arm. This afternoon I'lltake the belt off first, then if it's still ticking, I'm going to remove the valve covers

 

[jasonmd13]

Re: Fear the worse, loud banging sound comingfrom the engine

You say the oil was high: is it milky or does it smell like gas?

It does sound like a rod knock but sometimes sound from videos can be deceiving. Does the noise quiet down when you put the boat in gear? Often times a rod knock will quiet down a bit when under load and get louder when sitting in neutral. Also, when reving the engine in neutral a rod knock will often get much louder just after you let off the gas due to the load being taken off of the bearing.

The oil wasn't milky, or smelly. The sound stays the same now. When it was popping so loud, the more gas I gave it, the louder it was, in gear or in neutral