White smoke, burned rubber smell

[JASinIL2006]

Hi all, I could use some diagnostic help with my engine.

My boat has a 350 Mag Alpha One Gen 2 (serial #s in my sig below). Boat is freshwater cooled. I ran it on muffs this morning to get it warmed up and everything seemed to be OK. (Except for a dead battery due to my daughter leaving the stereo on....) Took the family out last weekend (first real outing of the year) and the boat worked flawlessly.

Today, when warming up the engine at the dock after launching, I thought I saw a whiff of white smoke in the engine compartment. The wind was blowing right over the stern, though, and I thought it was maybe exhaust getting blown back into the boat. We idled down a small channel, got up on plane and made it to the main channel of the river. We then idled for about 5 minutes. Just to check, we opened the engine compartment and saw considerably more white smoke, smelled burning rubber and decided to head back in. During this time, the temp gauge was right where it normally is, about 160, and none of the other gauges showed anything unusual.

When we were back at the dock a few minutes later, there was still a bit of smoke and the smell of burned rubber, but not as bad as when we were out on the river. I could not see where the smoke might be coming from. I did feel the water hoses on the engine; the large lower hose on the starboard side of the engine was very warm. Not too hot to touch, but very warm. Exhaust manifolds were a little warm, but not much.

The belts looked OK; all the pulleys were turning, without any squeaking or squealing, and when I checked later, all are tight.

My first suspicion was the impeller/water pump in the outdrive, but I just pulled the drive, cracked it and removed the pump. The impeller and everything in the drive look fine. (I replaced the entire pump assembly about two years ago.)

Any idea of what I should check next? I'm a bit apprehensive about going back out on the water until I'm sure I've figured this out.

Thanks!

Jim

 

[1ruralmailman]

smell of burning rubber is usually the teltale of a spun coupler.i would imagine hade you ran it longer there would have progressed to the feeling of sluggishness,and overheating.only way to know for sure and repair is pull the motor.good luck,hope i a wrong.

 

[Fun Times]

smell of burning rubber is usually the telltale of a spun coupler. I would imagine hade you ran it longer there would have progressed to the feeling of sluggishness, and overheating. Only way to know for sure and repair is pull the motor. Good luck, hope I a wrong.

While reading the post, I kept thinking possibly the engine coupler as well. Maybe try looking behind the engine to see if you can see any excessive rubber black particles, debris building up.

Has the coupler been greased?

 

[Bondo]

While reading the post, I kept thinking possibly the engine coupler as well. Maybe try looking behind the engine to see if you can see any excessive rubber black particles, debris building up.

Has the coupler been greased?

Ayuh,.... Ditto that,....

 

[JASinIL2006]

No sign of Black rubber bits back there... I am thinking I forgot to grease the coupler from the engine side zero the Spring when I de-winterized... I was hurrying to get the drive on after winter storage to get the boat in to a shop to deal with a backfiring problem from last year. I don't think I lubed it.

 

[JASinIL2006]

If the problem is the coupler, do you think running the engine without the drive installed would put enough load on it to see if I can recreate the smoking? I lubed the heck out of the coupler via the zerk, and I'd like to be sure the coupler is the problem before I pull the engine.

I necessary, I can put the drive on and run it, but if I can just stick a hose in the water intake and run it without the drive, that would save me some time.

 

[nateo]

I doubt if it's a coupler. if you've spun a coupler I can't see there being any power to the drive at all. One way to tell if coupler is spun is to turn engine off. Put drive in forward gear and try turning the propeller counter clockwise(with engine off). If prop keeps spinning then it's coupler.

Burnt rubber spells can also be exhaust flappers in a overheating situation.

 

[nateo]

If the problem is the coupler, do you think running the engine without the drive installed would put enough load on it to see if I can recreate the smoking? I lubed the heck out of the coupler via the zerk, and I'd like to be sure the coupler is the problem before I pull the engine.

I necessary, I can put the drive on and run it, but if I can just stick a hose in the water intake and run it without the drive, that would save me some time.

Yes, while you have drive off try running engine on hose.

 

[nateo]

One last note about coupler. There's no in between that I know of. It's either spun or it isn't. If it's spun boat no go. You'd know if its spun. engine would spin with no resistance.

 

[JASinIL2006]

Well, I just ran the motor with a garden hose in the water intake until the engine got up to temperature. Once at temp, I gradually increased the throttle up to 2200 RPM. No smoke. No burned rubber smell.

I guess the next thing is to re-install the drive and try turning the prop CCW while in forward gear.

It still is sounding like coupler issue, but I wonder why I didn't have any loss of power or overheating if the coupler was slipping.

 

[nateo]

Did you get water coming out of bell housing as it should? The coupler is basically a big rubber bushing with splines in middle to accept drive shaft. When mine went at end of last summer boat wouldn't move at all and rubber pulled out of coupler housing.

 

[JASinIL2006]

Yes, hot water was coming out of the relief ports and the exhaust port. Coupler (viewed thru gimbal housing) was spinning. Of course, it had no load on it, so I don't feel too excited about that.

I inspected the out drive and there seem to be no blocked water passages and no sign of overheat. Nevertheless, since I have it apart, I'm going to replace the impeller. As soon as the impeller gets here, I'll reassemble the drive and see if the coupler slips when I turn against it by pushing on the prop.

 

[JASinIL2006]

So... I re-installed the outdrive today, and tried turning the prop CCW wile in forward gear (with engine off, of course). no slip whatsoever. Ran the engine in the driveway on muffs for a good 20 minutes. got the engine up to operating temp - 160 - and let it stay there a while. No smoke, no burning rubber smell.

I then took the boat to the Mississippi, idled for 10 minutes at the dock, then ran ii at a variety of RPMs for an hour or so. No smoking, no burned rubber smell. Boat ran great, had excellent hole shot, and hit the usual top speed at WOT for the prop I'm using.

the only thing I can attribute the white smoke and burned rubber to would be a coupler that needed to be greased and or running the boat with the drive trimmed out too far. sound plausible?

I can't think of anything else I did that would have corrected the problem. What do you all think?

 

[Fun Times]

Hopefully the grease helped solved the problem.

Engine alignment bar went/slid in and out nicely?

Old impeller looked good?

What's the need to be over trimmed at speed? Sandbar?

 

[JASinIL2006]

Everything looked good... alignment is spot-on (I check every year before I put the drive back on), the impeller looked fine, as did the pump housing.

The day the boat was smoking, I launched at a dock where access to the river involves running a quarter-mile chute that is only about 2' (sometimes a bit less) deep; the protocol is to trim up high, get on plane, and skim out to the main channel.

Last season, my trim limit switch went bad, and rather than tear everything apart, I just jumpered the switch. I wonder if maybe I was just trimmed to high for that speed? I didn't hear any protests from the u-joints or anything, but maybe the smoke was from the coupler getting stressed to much? Or maybe the coupler just needed to be greased.

In any case, I'll be keeping a close eye on it. I'm sure hoping it's OK and I don't have to put on a new coupler.