Burning Rubber Smell Comes and Goes

[greg82255]

Hi All,

I'm running a pretty powerful 383 through a 1986 Mercruiser Alpha One setup. Alpha drive is brand new last year, U-joints and all. On the lake 2 weeks ago I noticed a burning rubber smell, shut off the engine, opened the hatch and saw a little white smoke, but couldn't see any issue, started back up and the smoke/smell went away and didn't come back the rest of the day on the lake. A week later, the next time I took the boat out, about 3 hours into cruising around, the smell came back. Again I shut off the engine, saw white smoke, couldn't find anything, and it went away.

I fear a problem is developing that will one day become much bigger than it is now. Any guesses what it might be? I thought maybe the coupler, but doesn't that either work fully or not at all? Any insight and/or troubleshooting methods would be appreciated.

 

[alldodge]

Hi All,

I'm running a pretty powerful 383 through a 1986 Mercruiser Alpha One setup. Alpha drive is brand new last year, U-joints and all. On the lake 2 weeks ago I noticed a burning rubber smell, shut off the engine, opened the hatch and saw a little white smoke, but couldn't see any issue, started back up and the smoke/smell went away and didn't come back the rest of the day on the lake. A week later, the next time I took the boat out, about 3 hours into cruising around, the smell came back. Again I shut off the engine, saw white smoke, couldn't find anything, and it went away.

I fear a problem is developing that will one day become much bigger than it is now. Any guesses what it might be? I thought maybe the coupler, but doesn't that either work fully or not at all? Any insight and/or troubleshooting methods would be appreciated.

Is this is full run cruising for 3 hours or cruise for 20 to 30 minutes, sit a bit and cruise some more? If your doing a lot of high speed runs and you haven't already you need to look into an external oil cooler and a drive shower

 

[greg82255]

Cruise for 20/30 min, sit a bit and cruise some more. I intentionally haven't done any high speed runs (3500-4000 rpm is the highest I've taken it in recent weeks). I do also have a drive shower but no oil cooler.

 

[alldodge]

Cruise for 20/30 min, sit a bit and cruise some more. I intentionally haven't done any high speed runs (3500-4000 rpm is the highest I've taken it in recent weeks). I do also have a drive shower but no oil cooler.

In that case I hope it's not your coupler. If your boat is fairly light it might just be slipping a bit but not enough to stop the prop, not that this is the issue. Most couplers when they slip there done.

Check your exhaust boots and see if any are soft, maybe low water flow on one side

 

[greg82255]

Thanks. I'll definitely check the exhaust boots. Is there a way to tell if the coupler is on its way out without pulling the engine and looking at it?

Any other possible sources of burning rubber? I can say for sure it's definitely not the belts.

 

[Rick Stephens]

If you can see and reach your drive shaft behind the engine, crank your motor around until the timing mark on the harmonic balancer is at TDC. Then reach in with a piece of chalk or a paint marker and mark the drive shaft. If the coupler is bad that mark will change in use.

Rick

 

[tpenfield]

My first thing to check would be the exhaust boots, as stated. Also, are you noticing any spikes in the temperature gauge? The exhaust boots will start to smoke pretty quickly if they aren't getting any water out through the exhaust . . .

 

[Eric 3.7LX Alpha 1]

If you can see and reach your drive shaft behind the engine, crank your motor around until the timing mark on the harmonic balancer is at TDC. Then reach in with a piece of chalk or a paint marker and mark the drive shaft. If the coupler is bad that mark will change in use.

Rick

Nice way to check it.... :thumb:

 

[Scott Danforth]

exhaust boots have a max temperature of 250 degrees. just takes a burp in the water supply to the manifolds to cause the rubber to start to get crispy.

 

[greg82255]

If you can see and reach your drive shaft behind the engine, crank your motor around until the timing mark on the harmonic balancer is at TDC. Then reach in with a piece of chalk or a paint marker and mark the drive shaft. If the coupler is bad that mark will change in use.

Rick

Interesting idea. I see what you mean and will definitely give it a try.

The temperature gauge remains constant, right around 160.

Would an exhaust boot heating up cause white smoke in the engine compartment..? Or would any smoke just go out the exhaust?

 

[alldodge]

Interesting idea. I see what you mean and will definitely give it a try.

The temperature gauge remains constant, right around 160.

Would an exhaust boot heating up cause white smoke in the engine compartment..? Or would any smoke just go out the exhaust?

Don't see burning rubber being white, but steam from the exhaust would