Strange noise from motor

[Chamelion]

Hi all,

Clips here... Fairly self explanatory.



I've tried replacing the spark plugs.. Will water test tomorrow to see if it's made a difference. This clip is after replacing the plugs.. I figured I would see if it was perhaps a plug not getting spark. All leads gave me a shock, hence the pliers being used for the clip. lol. Even tried switching around the CDM units between cyls 2 and 3 to see if it would make any difference. Nothing noticeable.

I did find it strange that it would run on 1+2 (just), 2+3 (fine), 1+3 (fine), 3 only (rough, but fine).



I've used this guide to make sure it's not the same problem.. I'm confident that it's not.



Note: I don't have any play when doing this test, none at all.

I've been using the correct 50-1 fuel-oil ratio. Two tanks of valvoline since purchase, half a tank of Quicksilver.

I usually use 91ron, video taken with 95ron and the noise is the same. I do not use fuel with ethanol.

Could it be something loose around the drive shaft area? Does sound to be coming from somewhere above the waterline. I'll do the screw driver stethoscope trick tomorrow to see if it's coming from inside the powerhead or not.

If I can work out the cause I guess I'll just have to take it to a mechanic.. Just not keen on spending any more on her at the moment. After the purchase and the hull repairs I need a month or two to recoup. >.<

Cheers

[astro66]

thats the sound of your wallet opening.............

[Chamelion]

Thanks...

A bunch...

[brock13]

Sounds like when i hit the kill switch when in motion and in gear. Wish i could help

[Chamelion]

Sounds like when i hit the kill switch when in motion and in gear. Wish i could help

I get that noise too, but it's normal for these motors... The noise I'm hearing isn't.

Will be absolutely devastated if the motor requires major mechanical work, I just don't have the money.. I thought I was pretty thorough in checking it out before I bought it.

Been sitting on youtube for AGES trying to find a clip that contains the same sound, let alone one that where the answer is also shared.

[Chamelion]

I've been reading as much as I can about rod bearings and how to diagnose them.. I can't find any play in them whatsoever.

[Chamelion]

I'd just like to add that it doesn't seem to do it whilst running on muffs. It certainly didn't today.. I did do the stethescope trick around the side of the motor where the spark plugs are and everything sounded hunky dory inside. I'll check other areas tomorrow.

I'm wondering if it might just be a loose exhaust or something else simple.

[Tracker]

IF it was a chrysler I would say death rattle(loose gudgeon)
BUT seeing as its black, maybe a corrosion hole in exhaust tube. I had a 50 that did that.It made the noise mostly when backing off with NO load.
How many hours(appox) and have you owned it since new?
I think the only way to be sure is to split the case and have a look.

[Chamelion]

Hours are anyones guess.. Have owned it for a little over a month.

Ran it on muffs just now, it's not making the noise at all. Surely if it were a rod bearing or the like it would do it regardless if it is on muffs or in the water?

About to go and give it a run on the water anyway.. See if if it's only once it has warmed up or only in the water etc.

[Fed]

Did you get the tacho?
wrap the lead around each plug lead (one at a time) and take it for a run.
I bet it's dropping spark.

[astro66]

is it pumping water when its making that noise??? maybe the keyway has come out of the impeller....with the muffs on the tap pressure spins the impeller so it doesnt make that noise........has it been changed/serviced ???

That is a wicked noise though...you might be lucky...but if that was a two stroke bike i would be crying with that noise....
But i know when the bearing start to go you will get a similar rattle in nuetral as you back off and at some rpms in gear ......

[Fed]

FWIW my theory is that it's losing spark and then detonating at maximum compression instead of firing when it's supposed to (BTDC).

That 'clacking' noise is hard to forget for an old rev head.

[Chamelion]

Haven't got the tacho yet... Still a couple of weeks away I'd imagine.

It is pumping plenty of water both on muffs and out on the water.

Took it for a run today for a few hours... Notes:

Happens in neutral and reverse at medium revs. At idle it's fine.
In FWD it doesn't happen until I back off the revs. I can reliably power up, back off a bit to make the noise occur, power up a little and it goes away, drop back and it comes back again. If I drop revs until the noise starts I can hold it in that throttle position and the noise will stay. Go faster again it it goes away, slow right down and it goes away.
At about 3/4 throttle the engine becomes noticeably louder and at the same time you can feel a surge in power (just the powerband coming in to play?) - There is no rattle or clunking at this point though.

[Chamelion]

http://www.themarinedoctor.com/cgi-b...m=1314065520/0

Appears to be a similar issue.

[Chamelion]

Update: Just ran it on muffs.. No noise at all. Blocked the through hub exhaust with my hand (firmly) and gave it a few revs and bingo, rattle was there.