Loud tapping noise when accelarating under load 3k rpm

[baker556]

Hi all,

First time I've been out on the boat this season after some routine maintenance. Including risers, gimbal, oil sparks, outdrive oil change - standard servicing really.

The boat under slow speeds, no issues at all, when accelerating getting up to 3k rpm or there abouts, there is a loud tapping noise, almost sounds like ball bearings in a coffee tin.

Some things to note, I've had the boat from new, never touched the timing, rockers or tappets.

Boat wasn't used last season, has fuel and fuel stabiliser from 2020 season, mixed with 30 litres of new fuel.

Everything else works as it should.

Boat info as follows - year 2003:
Engine details:
Volvo penta 3.0 GSP-C
Holley carb
3869148
4012075270
Transom Assembly

TSK SX-M
3868844
4151015896

Drive Unit
SX-M 1.97
3868895
42020620
If anyone has any thoughts or ideas, that would be really appreciated!

Thanks

 

[baker556]

Also to note I can't reproduce this noise just revving the engine, only when under load out on the water. I'll try and post a video later today.

Thanks

 

[racerone]

edited

 

[Bondo]

Ayuh,..... Sounds like detonation, usually from bad fuel, a lean condition, or bad timing,....

 

[baker556]

You think so bondo, could that damage anything like pistons? Would that not show on just reving without a load?

 

[baker556]

I've tried to get a video of this attached here. I think it could be exhaust riser related as I replaced this. However its very difficult to pick up this exact sound on a phone camera.

It's very apparent when driving.

As can be seen in the video there is a lot of shaking around the exhaust area, I've never really taken note of that assume it's normal?

Thanks

 

[baker556]

I'll also add that she is quite hesistent to start.

Needs quite a lot of throttle even when warm to get her going. This is with new spark plugs too.

 

[baker556]

OK new update here. Still unclear what the noise it but dampens down when going quicker.

Just concerned on opening her up if it's something more sinister.

 

[baker556]

Still think could be exhaust related, any further thoughts from the experienced people on here?

Would bad fuel cause any future issues with wear and tear?

Thanks

 

[Bondo]

Still think could be exhaust related, any further thoughts from the experienced people on here?

Would bad fuel cause any future issues with wear and tear?

Thanks

Ayuh,..... Holes in pistons,......

What do the spark plugs look like,..??

 

[baker556]

That's my concern bondo. I can go slow without any noise, increase speed to 3k rpm then the sound happens, after increasing beyond it stops. Would you still think that's the result of bad fuel? Should it not happen all of the time?

I'll check sparks today.

 

[baker556]

Sparks look clean and fine.

Check the video out I've uploaded to this post sounds like more toward the outdrive now?

The outdrive was off earlier in the year everything aligned and bolted back up and torqued properly.

 

[Bondo]

Sparks look clean and fine.

Check the video out I've uploaded to this post sounds like more toward the outdrive now?

The outdrive was off earlier in the year everything aligned and bolted back up and torqued properly.

Ayuh,..... Clean spark plugs, ain't good,.... Any grey specks, or rounded edges,..??

Good plugs are cream in coffee brown,....

Only sounds I hear in yer vid is bubblin' exhaust, 'n protestin' u-joints, bein' trimmed up so high,....

 

[baker556]

Cheers Bondo - with the sound of the U-Joints protesting, it's not something I've heard before, hence bringing this new sound up. Must be something going on there.

 

[baker556]

Hi all,

Volvo Penta 3.0 GSC-P 250 hours 20 years old making a noise deep in the engine around 3k rpm worse under load at sea.

So far replaced or checked,
U-joints
Gimbal
Raw water pump
Circulation pump
Rebuilt carb

I wrote this thread last year:

Loud tapping noise when accelarating under load 3k rpm

Hi all, First time I've been out on the boat this season after some routine maintenance. Including risers, gimbal, oil sparks, outdrive oil change - standard servicing really. The boat under slow speeds, no issues at all, when accelerating getting up to 3k rpm or there abouts, there is a...

forums.iboats.com

Bondo suggested detonation, I'm leaning towards this more than ever, therefore assume I need to time the engine.

Is there any particular tool that I should be using to time this?

TIA

 

[baker556]

To add to this, the engine runs on only for a very short time, but worth mentioning.

 

[alldodge]

To add to this, the engine runs on only for a very short time, but worth mentioning.

As Bondo mentioned in first thread there is detonation going on, and the run on after shut down and hard start all lead to incorrect timing.

Don't have the manual for your motor but Merc timing can be anything from 1*BTDC to 2*ATDC depending on the serial number. Merc uses the Delco EST distributor and I think VP has the same.

What is the timing set at?

 

[baker556]

Thanks alldodge for confirming this is all starting to point towards timing.

Is it possible to use any timing light to perform this? Any good guides you know of?

Thanks

 

[baker556]

Adding more info here, spark plugs were black in colour

 

[alldodge]

Any timing light is good, but the advance type is easier. Also depends on how well you can see timing marks on damper

Color leads to running rich, might just happen more so at idle

To time EST need to connect shunt and by pass interrupter