2002 30hp Yamaha

[Oz Rosco]

G'day to the international Yamaha family . . .

I recently bought a 30 DMH 2002 Yamaha outboard, and have nearly got it sorted out.
I need help with the last problem . . . there is an intermittent knocking/clunking sound in the engine. It is a solid sound, like the driveshaft is trying to jump back into spline mesh.( Its very hard to describe a noise !)
I originally thought it might be the pinion bearing at the bottom of the driveshaft, but I discounted that by taking off the lower unit . . . and it still made the noise.
When I run it on the muffs, it only seemed to make the sound when it was quickly decreasing revs, rather than building revs. It does it in neutral and forward gear as well.
I took it for a short run yesterday, and found the noise to be more evident under normal load. I couldn't get past 1500 or so rpm without it clunking. It would rev smoothly for 10 or 20 seconds, but when I applied a little more power, it would clunk. It seemed that the clunk even led to the motor stalling a couple of times.
It has got me stumped. The motor will start easily and idle like a kitten all day long.

Any ideas greatly appreciated. I have been told to look at the flywheel and check it's correctly tightened.
I'm looking forward to the long Australian summer ahead . . and would love to have this Yammy running like it should !
Thanks again . . .

[boats.net]

Might remove cylinder head and check condition of cylinders and pistons, check rod bearing by bringing piston to top(just over TDC) and push on piston to see if moves downward any.

[Oz Rosco]

Thanks boat.net . . . I did a comp test today, and it was even all 3 on 100psi. I would have thought the numbers may have been higher, but at least they were even.
The motor is a pull start. Does a couple of pulls on the rope give a good comp reading ? I would guess an electric start might be a more accurate reading ?
I shone a torch down the plug hole, and could only see the piston top. It looked normal on all 3. Tomorrow I will buy one of those tech torches ( bulbs on the end of a thin flexible shaft ), and have a look at the cylinder walls.
I will check the rod bearing as you described.

Thanks for the help . .will let you know how I fare.

[Oz Rosco]

I took the motor to the tech today, and he located and fixed the problem.
It turns out the motor was only running on 1 cylinder ( amazingly, it started and idled on just the top pot ! ).
The timing was out of whack. The throttle linkage was advanced. Some electrics needed replacing/re-wiring.The reed valves needed a good clean.
The knocking was detonation in the crankcase.

And the best part ? . . . it only cost me $100 to fix it !!

Thanks for your input, boats.net.

[99yam40]

That just goes to prove that a timing light is a valuable tool when trouble shooting outboards and should be used more often.

What caused the motor to run on only one cylinder?
Fuel, reeds, bad electronics, or wiring problems?
And how did it get so far out of time?
Did someone start playing with the linkage?

[Oz Rosco]

99,
I bought the motor from interstate through a popular online auction site. Who knows what the last owner tried so it would run.
Buyer beware, I guess.
I don't know exactly which electrical components went south. I'm lucky enough to know a gentleman that is a retired marine mechanic. He took it to the yard he used to work at to run the electrical tests using the proper equipment and manuals.
I took it for a test on the water today, and it went great. Strong through all rev ranges and noticeably quicker than my old Johnson 35.
Luckily, I got out of this much better and less $$ than worst case scenario !

[99yam40]

Good for you ,I hope it gives you years of fine running and fishing.
He could not have had to replace very much for $100 unless he used secondhand parts he had laying around.
It would be nice to know what all was done just so you have an idea what to look at if it starts acting up again. I always have the need to understand what went wrong with something and what fixed it, but that is just me.

[Oz Rosco]

99,
I agree with you about not changing too much for $100. I look at it this way . . . I couldn't even get the flywheel off( without a holder). Even if he only cut a short out of a couple of wires, and re-ran them and still charged me $100. . . I'm prepared to turn a blind eye.
It went from running on 1 cylinder, knocking and clunking like a WW1 tank . . to running as it should .
Heck, even if he said " I can get this running well in 5 minutes, but it'll cost you a hundred . ." . .I probably would've paid him.
Let's face it, if I would've gone to the nice OEM dealer, they would have kept the boat for 3 days, charged me $450 . .and I still would be none the wiser as to exactly which parts they changed !.

But I would still like to know myself what the problem was. Maybe I will go for a visit with some beers and see if they can't help me get the truth out of him.
I'll let you know how that pans out.

[Oz Rosco]

A quick update . . .
I've taken the boat on a couple of trips since the fix. It performed well, and was pretty smooth across the rev range.
However, at idle on the muffs, it still exhibited the "knocking" that I guessed was a lean running situation. Backing out the adjustment screws didn't help.
When the motor was in the water under good operating pressure, the knocking didn't seem to happen. So I dismissed the knocking as only happening on the muffs, and so not that important. The idle was erratic with the coughing, etc . . . but it ran well in the water.
I was going to rebuild the carbs just in case. In sunny Australia, the 3 carb kit costs AUS $ 258.00 . . .around US$220 ? . . from the friendly Yamaha dealer.
As the friendly dealer performed CPR on my now lifeless form slumped at his sales counter, we got to talking about the motor. Long story short, I drained my tank of ethanol infected fuel, added some Yamaha fuel stabilizer to the new batch of regular unleaded . . and in an instant, the motor sounded like a miracle had happened ( just on the muffs, for now).
Idles smoothly and evenly. No coughing, spluttering or knocking.
Absolutely amazing difference. I couldn't get it to knock or cough even though I tried.
My advice to any of you who are having fuel related issues . . . do your best to avoid ethanol .

In Australia we do not have Seafoam or Stabil brand products. I've run Mercury Power Tune spray as my Seafoam, and now the Yamaha stabilizer as my Sta-bil.

Thanks again to the contributors on this site . . .

[robert graham]

Maybe the knock in the lower unit caused by not pulling up on drive shaft while installing those wave washers just above the water pump, to take the up and down slack out of drive line.
Go to: Bogueinletnc.com/yamaha for detailed instructions with photos on the water pump replacement procedure which mentions the importance of this step. Good Luck!

[99yam40]

A quick update . . .
I've taken the boat on a couple of trips since the fix. It performed well, and was pretty smooth across the rev range.
However, at idle on the muffs, it still exhibited the "knocking" that I guessed was a lean running situation. Backing out the adjustment screws didn't help.
When the motor was in the water under good operating pressure, the knocking didn't seem to happen. So I dismissed the knocking as only happening on the muffs, and so not that important. The idle was erratic with the coughing, etc . . . but it ran well in the water.
I was going to rebuild the carbs just in case. In sunny Australia, the 3 carb kit costs AUS $ 258.00 . . .around US$220 ? . . from the friendly Yamaha dealer.
As the friendly dealer performed CPR on my now lifeless form slumped at his sales counter, we got to talking about the motor. Long story short, I drained my tank of ethanol infected fuel, added some Yamaha fuel stabilizer to the new batch of regular unleaded . . and in an instant, the motor sounded like a miracle had happened ( just on the muffs, for now).
Idles smoothly and evenly. No coughing, spluttering or knocking.
Absolutely amazing difference. I couldn't get it to knock or cough even though I tried.
My advice to any of you who are having fuel related issues . . . do your best to avoid ethanol .

In Australia we do not have Seafoam or Stabil brand products. I've run Mercury Power Tune spray as my Seafoam, and now the Yamaha stabilizer as my Sta-bil.

Thanks again to the contributors on this site . . .

Sounds like you have got it lined out and running good.
The carb kit for my C40 cost me a little over $100 here in the USA, and did not need to replace the floats but put them in anyway. You may check to see what all parts you need to replace and see how much they cost individually compared to the kits, if you get to that point next time.

The coughing you spoke of is usually the indication of what they call a lean sneeze from plugged idel or pilot passages, but old fuel will do it too. Have a great summer down under.
The cold fronts are finally showing up here on the Texas coast and the flounder should start making their fall run, to bad they have lowered the daily limit to only 2 during November, but it will go back to 5 Dec 1st. What are you catching where you are at?

[Oz Rosco]

It was hard to describe the knocking in words. Some said the lean coughs could be "violent". And how right they were.
Robert, I have changed the water pump/impeller and I don't think my lil 30 has those washers above the housing. I will have a chat with the parts guy, and check it the next time I do the impeller. Thanks for passing on the tip. If we all let each other know the little things that fix our problems . . . it's bound to help !.

Yam 40, thanks for following this one through. I would not have called my fuel stale. I would have argued that I put the correct amount of oil/fresh fuel in before each trip. I would have defended myself by saying that I never let it run dry and suck the dregs thru the carbs.
However . . . . the difference that fresh fuel with the Yammy stabilizer has made is absolutely amazing. If it ran that much better if I had rebuilt the carbs . . . I would have been happy and justified the cost.
Now, as to the fish we catch . . you may have to google these.
I usually fish for the table, using light gear. We fish for bream, whiting, flathead and kingfish. And sometimes, we even catch them !!
Thanks again, all the best.

[99yam40]

You are lucky if you can get just plain unleaded there, we can not.
Or at least I have not found a place to get it for a couple of years thanks to our government.
Ethanol tends to attract moisture and cause a phase separation of the fuel after a while, that will layer out with the heavier water laden ethanol on the bottom. Guess where you pick up tube sucks fuel from, you are correct, it is the bottom. and then the rest of the fuel is lower octane because the ethanol was a octane booster that is not there anymore. A fuel stabilizer is a good thing to add to keep fuel fresh as long as you can and the main thing is to run the motor as often as possible and enjoy, even if you have to wear long sleeve shirts and pants and a coat if necessary. I have even got to the point that I will wear diver neoprene gloves to drive the boat just so I can feel my fingers when I get to the fishing spots.
I tend to fish salt water more than fresh, off shore and inshore, it is cheaper inshore running my C40 instead of the fuel hungry large motors. But I will fish fresh for cat fish, and white perch from time to time. Sure wish I was headed for summer time instead of winter.
Have a good warm fishing season and catch what you can eat and release the rest for next time.

[Oz Rosco]

99yam,
We must be doubly lucky. We can still get regular unleaded, and also premium unleaded. It has a higher octane rating.
I'm very conscious of over fishing. I generally don't keep more than 3 or 4 of each species. That is of course, when I can catch me 3 or 4 of each !