Slapping or clicking noise Mariner 90 Twostroke

[KOTARA]

Baffled by a clicking, ticking noise coming from Mariner 90 twostroke.
Doesn't happen until higher revs and under way.(No noise at idle or at higher revs out of gear). Can't reproduce out of the water using muffs.

Noise is a click every second or so, doesnt seem to increase much if at all as revs increase more. Had ear against cowl and doesnt seem to be from head end of engine. Maybe lower gear box or drive shaft but hard to tell.
Engine performs fine with no other issue but I'm not happy to carry on using it incase of major damage or failure.
I have a video of noise in action but system won't allow video upload.
Anyone know if I can upload somewhere and attach a link so it can be seen?
Any thoughts on what it may be would be most appreciated!
Cheers

[Steve509926]

Hi, load your video onto YouTube then post the link to the YouTube video on Ribnet.

[KOTARA]

Thanks Steve, I'll give it a go

[KOTARA]

https://youtube.com/shorts/Bz_yTOtCdfA?feature=share


Have uploaded a short video of the noise to Youtube, hopefully it works

[Steve509926]

hopefully those more experienced than I will take a look and come up with a possible cause.

[KOTARA]

Thanks for your help Steve! Much appreciated

[KOTARA]

I have drained the oil from the lower unit gearbox. No water in oil, in need of a change- maybe 100 hours..
Attached photos of magnetic plug, has a small (I think- but don't know) amount of metal.
Would this be normal wear and tear metal or more sinister needing strip down?

[Peter_C]

Fine metal like a dust would be considered normal wear. Those chunks of metal are not.

If it were me I would use an electronic stethoscope with multiple sensors clipped on or a regular one, and with the engine cover removed start moving it around to better locate the source of the sound. It is not a fast sound so its not emanating from the crankshaft area.

[Matt]

1. Does it have a mechanical oil pump? Or do you premix?
2. Does it do it at idle, in gear, under load?
3. Does it do it at idle, out of gear?
4. Does it do it in neutral, but raising the revs to whatever we heard there?
5. Does it do it in gear, at the same revs, no load (on the hose)

[KOTARA]

Thanks Peter and Matt
Looks like it could be the lower gear box then...will try to get a stethoscope.
Yes it has a mechanical oil pump- injected 2 stroke oil
No noise at idle or in gear at idle, can't hear anything on the hose when increasing the revs in neutral or in gear, fwd or reverse.
Can only hear the noise at higher revs 4000 or so forward motion on the water.

Any other suggestions welcolme before I strip the lower leg.
I'll try the stethoscope around the leg / lower gearbox with new oil first though.

[Matt]

I both agree with Peter regarding the chips - but probably only to the level, for now, of doing another oil change soon and seeing what's on the magnet again.

But I don't believe that's your noise.

Assume the frequency of your noise DOES correlate to engine speed (Forgot to ask above), let's say you were doing 3000 rpm in the vid - I'd expect any gearcase noise to either be directly correlated to engine speed - ie at 3000 rpm, ie ticking 50 times per second - or somewhere near half that (if propshaft related), or half that times 3 if prop related. Or a rumble if bearing related. But you are very unlikely to hear a "tick" from the bearbox, since the water muffles it all anyway.

So, based on what we hear, I think it's powerhead related, mechanical, but not at crankshaft rpm.

I'd be taking a look at the oil injection pump, noting that you said mechanical injection rather than the occasional seperate unit you could get back in the day. Now I'm not familiar with your specific engine, but generally oil injection runs off a worm gear on the crank and turns substantially slower than crank speed. It also often runs on a plastic gear - and this tick we hear could be a missing tooth somewhere.

On that basis, I'd get it properly diagnosed sooner rather than later - a failed oil pump would destroy the engine. But if that does end up being the diagnosis, then it's not to hard to switch to premix and continue running the motor for years to come.

Obviously diagnosing anything on the internet is a minefield and the only "real" answer is to look at it in the flesh. Happy to come and look if you want to sub me a business class ticket to pop over, but realistically, I am sure there are some competant local mechanics.

Other things that can make ticking noises - the solenoids for the starter and trim pumps. But if the starter solenoid was trigger, I'd expect us to hear the start gears gnashing.

But also, Peter could be spot on the money - it just doesn't "seem" like that - but we're all guess really without being there and having a poke round.

[beamishken]

I've been thinking of what this could be for a couple of days as its an odd one, I'd agree its probably not the box & the hairy plug just needs monitoring.
My theory is & its only a theory for discussion is whilst Matt's suggestion of the oil pump makes sense due to timing of the knock, I think its too heavy for an oil pump noise. I think its crank related, yes its too slow for crank speed but if one conrod has one or two damaged rollers with a flat spot or a rust mark it would only knock when the damaged roller(s) was at the top when the cylinder fires. The rollers rotate at far less than crank speed & each roller would only be at the top after several revolutions of the crank hence the slower knock. Obviously easier to explore the oil pump but thought I'd offer an alternative suggestion, if Matt's right its an easy ish fix but if its crank then it needs looking at sooner rather than later.

Sent from my SM-G950F using RIB Net mobile app

[KOTARA]

Thanks to all for taking the time to reply. Would be great to see you over here Matt - but can't stretch to a plane ticket for you If I win Lotto I will fly you over First Class and we can go out on my Super yacht for a fish!

I'm off to the local Boat / motor service guy this morning to see what he says- will let you know.
Pump theory- I would have thought that would show at all speeds and on hose too- but I'll check it out.
Also the frequency doesn't seem to change much, if at all, which is strange too.

I've found a large locking circlip that has come loose , it's captured on the gear shift shaft, - looks like it locks the steering mount pivot shaft - could be my noise if it's clanking away and knocking on the gear shift linkage. Could mean the whole motor is moving up and down on the steering mount too. I'll investigate further....

[Matt]

That needs fixing. Should go here.
But I'd expect that to be a "tinkle", rather than a steadily timed tick - but who the hell knows, eh.

Do you have answers to my questions above? Knowing if it's related to engine load and/or engine speed will be useful.
For example, of not related to engine speed, then both mine and Ken's thoughts are less likely.

[KOTARA]

Thanks Matt
Answers to your questions in red. Seems to point to geartrain, gearbox or mount knocking under load but still not sure...can't think of anything rotational that doesn't seem to increase in frequency with increase in speed and only starts at higher speed in gear...
1. Does it have a mechanical oil pump? Or do you premix? Mechanical oil pump
2. Does it do it at idle, in gear, under load? Only in fwd gear at higher speed- I think starts at about 3000RPM (A bit deaf so will have to take younger ears or stethoscope to be sure)
3. Does it do it at idle, out of gear?No
4. Does it do it in neutral, but raising the revs to whatever we heard there?No
5. Does it do it in gear, at the same revs, no load (on the hose)No
I spoke with a very experienced boat mechanic - he watched the video - said he didn't think it was oil pump and didn't think it was a bearing noise but without checking himself couldn't give further advise.
He said the circlip coming off was common and not major- said the groove on shaft area corrodes and circlip will come off if refitted. A common fix is to drill and tap case to the bush and fit 2 bolts to take up the play.
He was concerned about so much metal from gearbox mag plug and recommended replahttps://www.rib.net/forum/images/smilies/smile.gifcing or reconditioning gearbox although he didn't think that was the cause of the noise.
I've removed the circlip and put fresh oil in the gearbox. Will take it for a run with a driver with good ears and and a stethoscope - cowl off when work and weather permit -see what more I can find out.
Reluctant to replace gearbox until I know whether there are other issues.
Cheers
Carl
Kotara is the boat name- (Kingfisher in Maori)

[KOTARA]

Thought I'd follow up on my engine noise for anyone interested... I know it's been a while but thanks to those who had a go at the diagnoses .
It was the lower leg gear box- I eventually found a second hand one off a 60 HP that uses same leg. Swapped it out and it runs fine with no issues!
Cheers
Carl

[smallribber]

Originally Posted by KOTARA

Thought I'd follow up on my engine noise for anyone interested... I know it's been a while but thanks to those who had a go at the diagnoses .
It was the lower leg gear box- I eventually found a second hand one off a 60 HP that uses same leg. Swapped it out and it runs fine with no issues!
Cheers
Carl

Well done. Sounds like a result 👍