Tohatsu 4 hp thumping noise

[blacksmithden]

Sorry if you're reading this twice guys...I had it posted in the wrong section.


Good day all. Well, the search didn't reveal anything, so here's my problem

I have a Tohatsu 4.0hp with about 12 hours on it. It's a 2011 model, bought new 2 months ago. The last time out, right from the get go, it had this thumping noise. The speed of it goes up and down with the engine speed, but doesn't match the engine RPM by a broad stretch. It will do this in forward, neutral, and reverse, and its not intermittent. Running it in a barrel in neutral, and reaching down with a broom handle to stop the prop completely doesn't make any difference.

In the one video, it's pretty hard to hear. Listen for the locomotive CLUNK, clunk.................CLUNK, clunk. It's easier to hear in the video where I'm tapping my finger on the edge of the barrel in time with the clunk.

I was a professional auto mechanic for 11 years, and have been professional heavy equipment mechanic for the past 14. I've also had a professional marine mechanic with over 20 years experience listen to this video. Neither one of us have every heard an outboard make this noise before. It's under warranty, and I'll take it in if I have to, but I usually just fix my own stuff rather than leave it in a shop for weeks on end. If anyone has experienced this noise before, I'd really appreciate hearing about it before I start tearing into this little guy. Thanks....blacksmithden.....

Edit: Ooops...only allowed one video in a post. No problem..the second one is where you can hear the noise better anyway.

 

[Davem3]

Re: Tohatsu 4 hp thumping noise

i am going to wait for the guru's to chime in on this one, i have a brand new 6HP, and never heard that noise before........... how many hours on here, and how is the oil level in her????

waiting on Paul and Elvin ............. also, you are doing the break in correctly, right ?????

 

[blacksmithden]

Re: Tohatsu 4 hp thumping noise

i am going to wait for the guru's to chime in on this one, i have a brand new 6HP, and never heard that noise before........... how many hours on here, and how is the oil level in her????

waiting on Paul and Elvin ............. also, you are doing the break in correctly, right ?????

It didn't have that noise during it's break in, or on it's first few trip.

The breakin was done in that barrel, in my yard. The neighbors must have thought I was nuts running an outboard for 10 hours in the yard. LOL. I figured I'd get the break in out of the way under controlled conditions. It got an oil change after the first hour, and at about hour 5, then another one at the 10 hour mark. It got another one after it's first trip out. It only holds 1/2 liter, so it's not like it's expensive. The bottom end oil got changed at the same intervals as the engine oil. The remaining (estimated) two hours of running time have been done mostly at idle, or just off idle speed with intermittent shots of higher throttle. It wasn't hard to mind my P's and Q's as there was still a fair bit of ice floating in the river. Oh..and the engine oil level is right where it's supposed to be.

 

[TOHATSU GURU]

Re: Tohatsu 4 hp thumping noise

Sounds like the prop bouncing off the side of the tank that is too small to run the engine in

 

[dtj]

Re: Tohatsu 4 hp thumping noise

Look at the motor/tiller handle as it rotates at the same oscillation rate as the finger tap, your barrel setup with plywood clamp to a round surface is absolutely no way to identify an inappropriate thumping sound which is probably a motor part bumping against the barrel surface in this oscillation rotation motion.

Show us a video of the motor properly mounted on the boat or a very rigid large barrel setup with the same thumping sound.......Don

 

[blacksmithden]

Re: Tohatsu 4 hp thumping noise

Thanks for the replies so far guys, but the prop isn't hitting anything and the mounting isn't the issue. It makes the exact same sound when it's mounted on the back of my flat back canoe. Changing the trim angle also makes no difference. Putting it up in the shallow water drive position makes no difference either.

Like I said in the orignal post....leaving it in neutral and stopping the prop completely with a broom handle doesn't change the sound at all. It's 100% internal to the unit and has nothing to do with the prop or the prop shaft. Unfortunately, the way the sound is tunneling through everything, I can't even isolate it to the power head, leg, or lower unit.

 

[Star]

Re: Tohatsu 4 hp thumping noise

I understand why you wanted to break it in in a barrel but I don't think 10 hours without hitting 4,000 rpm would be good for the motor.
Many here tell how they go WOT in a barrel. Even 3000 could kill water circulation to the motor.

 

[pvanv]

Re: Tohatsu 4 hp thumping noise

Does it make the thump with the cowl off? I'm not sure, but it sounds like something is clunking around, as Elvin mentioned, in the barrel. Is the prop nut tight? Maybe something loose sloshing around in the LU, or something (such as a throttle cable) loose inside the cowl. The frequency seems too slow to even be at cam speed, so I doubt it would related to the fuel pump, but worth investigating. If you run with the cowl off, you may be able to pinpoint the source a little better with a mechanic's stethoscope. Could even be the shift linkage dancing around. You may well end up at the dealer for diagnosis.

 

[Sea Rider]

Re: Tohatsu 4 hp thumping noise

A real exaggeration to change oil for so many times for the motor not hitting open water once, needless to say break in period on a barrel, doing so can overheat engine as water will have excesive temperature working on a merry go round barrel, you definitely have not read the owners manual once. Is the sound same with cowl on/off ?

Happy Boating

 

[blacksmithden]

Re: Tohatsu 4 hp thumping noise

A real exaggeration to change oil for so many times for the motor not hitting open water once, needless to say break in period on a barrel, doing so can overheat engine as water will have excesive temperature working on a merry go round barrel, you definitely have not read the owners manual once. Is the sound same with cowl on/off ?

Happy Boating

Just thought I'd follow up. It turned out to be the down shaft bearing right above the gear box. Tohatsu ruled it a faulty bearing right from the get go and it was repaired at the dealer...no charge. Had nothing to do with the break-in method as they're a precision made part right from the get go. The water in the barrel never got warmer than some of the ponds around here at the height of summer, so that's a fairly poor conclusion to come to without knowing what climate it's being run in. If you'd bothered to actually closely read the posts, you'd have noticed I said that there was still ice in the river near here. As far as changing the oil....there's no such thing as changing oil too frequently...especially when you get it almost for free (note the bit about me being a mechanic).

Happy Boating right back at ya.

 

[pvanv]

Re: Tohatsu 4 hp thumping noise

Ah... you have a Long unit, that has the driveshaft bushing in the driveshaft housing... Unusual for a new one to be bad, but I'm glad they found it straight away, and got it straightened out. I take it the bushing had too much clearance (allowing the driveshaft to slap occasionally)?

 

[TOHATSU GURU]

Re: Tohatsu 4 hp thumping noise

I've never even heard of one being bad I bet the holder was not installed correctly allowing the slack to cause the noise.