Motor sound changed. Change is bad

[DaveC426913]

Did you ever figure out what it was?

Haven't been back to her yet.

[DaveC426913]

Still no clues.

I took it out again on the weekend. Still makes the noise. I ran it up to full power for a nautical mile or so. Hit 10knots with two of us. (Maybe time to clean the hull)

When I was putting her to bed, I saw oil/fuel slick around the stern and an inspection revealed oil smeared underneath this port:



I do not know if this is related to my noise problem, but I assume nonetheless that leaking oil is bad.

[Be Free]

The part you have marked is an exhaust port. You should not have oil in the exhaust at all so something is wrong.

Most of the exhaust comes out through the center of the hub so anything you see on the upper port should also be happening under water. Can you see or feel any oil inside the hub? Do you see blue smoke coming out of that port when the engine is running?

[DaveC426913]

The part you have marked is an exhaust port. You should not have oil in the exhaust at all so something is wrong.

Good to know.

Most of the exhaust comes out through the center of the hub so anything you see on the upper port should also be happening under water. Can you see or feel any oil inside the hub?

What's a hub?

I have not noticed any oil coming out underwater. I assume I should have seen a very obvious slick if it were just exiting into the water. What I saw when coming into my slip was what I'd expect from just a drip or two. And it certainly was coming from the smear at the upper port.

Do you see blue smoke coming out of that port when the engine is running?

No. I did not look specifically, but I suspect I would notice if there were any amount of smoke coming off the back.

[OverEasy]

Hi DaveC426913!

As your engine is a bit older (if I recall correctly) some drips are bound to occur but should generally be fixable.
No your engine shouldn’t leak oil.
It’s probably something gradually working it’s way loose or a seal that has aged out and is leaking.
Or just as likely you may have spilled oil at some point along the way, it’s pooled somewhere and it’s seeping out.

If the engine exterior is entirely oil leak free but your still getting oil drips from the port you may have an internal to the engine issue such as worn bushings, seals or guides that is allowing oil to get into the crankcase vent and blown out the port. That’s a potentially bigger issue and it may be worth talking to an actual experienced certified Honda Outboard mechanic.

Just a suggestion…

Best Regards,
Over Easy

[Be Free]

Most of the exhaust comes out through the center of the hub so anything you see on the upper port should also be happening under water. Can you see or feel any oil inside the hub?

What's a hub?

The hub is the center of your propeller. Most of the exhaust comes out of there.

I have not noticed any oil coming out underwater. I assume I should have seen a very obvious slick if it were just exiting into the water. What I saw when coming into my slip was what I'd expect from just a drip or two. And it certainly was coming from the smear at the upper port.

I'm out of town for the next day or so and I'll check my Honda when I'm back but my recollection is that any oil coming from the exhaust port will be coming from the combustion chamber. Oil that leaks anywhere else (like blowing up through the filler tube) will collect in the bottom of the upper unit and drip out of a weep hole. It's possible that there is a way for oil that has leaked into the cover may have a path through the cover and down to the exhaust port.

All of the oil you are seeing now may be from the time you reported that the oil "gushed" out when you removed the dip stick.

[DaveC426913]

I went out today. Kept it under 5 knots.

Zero sign of oil leak, zero sign of oil smudge under exhaust.


(Did collect about 600 pounds of seaweed on my blades in the lagoon. Boat ground to a complete halt a dozen feet from dock. Zero steerage, zero motion. In fact, I started drifting sideways, pulled by the weed in the current. The pitfalls of boating in late August after a super hot July.)

[Russ]

(Did collect about 600 pounds of seaweed on my blades in the lagoon. Boat ground to a complete halt a dozen feet from dock. Zero steerage, zero motion. In fact, I started drifting sideways, pulled by the weed in the current. The pitfalls of boating in late August after a super hot July.)

Wow!

At least you have a boat that you can lift the blades up.

[Be Free]

Good news!

I just finished testing. There are passages that allow water in the top of the engine to drain into the collar where the exhaust port exits. The water drained exactly under the exhaust port.

What you saw was likely residual oil dripping down from your original "gush".

[DaveC426913]

Thanks! That's a relief!

[DaveC426913]

Went back in the water. Never did get her to a repair shop over the winter. My local wanted to take the motor off the transom to repair it. I'd rather not.

So, I pulled off the flywheel cover. The rubbing is louder. It sounds like something rubbing on the underside of the flywheel - i.e. outside the engine block.

Finally managed to get a good audio recording of it:

If it's a doable thing by a simpleton, I'll take the flywheel off.

Does the flywheel and belt have any sort of tooth calibration thingy - like a TDC or something? Any precautions before I take the bolts out?

I tried with a small socket wrench. I may need a bigger socket wrench. And I guess I may need a torque wrench to put it back on correctly.

[Be Free]

Before you do anything, look at the timing belt. Make sure it's not starting to fray and slap something under the flywheel. I don't think that Honda has a specified replacement interval but they do recommend regular inspection. Remember: this is an interference engine. If the belt breaks the valves and pistons will almost certainly hit one another.

Another important thing to remember about the BF40 and BF50 is that they run counter-clockwise (looking from above). That is different from most other engines. Turning it backwards you have a good chance of damaging the water pump impeller.

Taking off the flywheel is easy. Remove the 4 bolts in the center of the flywheel and lift it off. You will need to immobilize the flywheel to get them out. I've used a pry bar across the bolts to hold it while I break them loose. If you do it that way keep them in until all of them are broken loose.

Pulling it off is easy. It's not a taper lock or woodruff key so you don't need a puller. There is a locating dowel on the underside. It might stay in the flywheel flange, it might stay in the crankshaft, it might fall out altogether. Just keep an eye on it so you can make sure it's there when you put it back together.

Putting the flywheel back on is even easier. Just make sure that the dowel engages the flywheel and the crankshaft. Torque to 48 ft lbs. If you don't have a torque wrench, make them "good'n tight". That's between "pretty snug" and "real tight").

The only thing I remember being under the flywheel is the timing belt, a tensioner, and a couple of coils. One is for the ignition and one is for the alternator. Both of them are wrapped in a cloth-like material. If they have started to unwrap that might be the noise you are hearing. I horribly overheated a BF40 once and made the alternator coil come unwrapped.

If I was going to guess, I'd say you might have a timing belt tensioner that is too loose or wearing out. If that is the case you should strongly consider replacing your timing belt at the same time.

It's not hard to replace a timing belt but it has to be done right. If it comes to it I'll post instructions and you can decide if you want to do it. Under no circumstances should you rotate the flywheel or the camshaft while the timing belt is off.

[DaveC426913]

Thanks. This is ultra-helpful.

Just knowing I can take the flywheel is a big relief.

Before you do anything, look at the timing belt. Make sure it's not starting to fray and slap something under the flywheel. I don't think that Honda has a specified replacement interval but they do recommend regular inspection.

I will do that. That's the big one with the teeth, right?

Remember: this is an interference engine. If the belt breaks the valves and pistons will almost certainly hit one another.

Should I be alarmed if I have never heard of an interference engine?

Another important thing to remember about the BF40 and BF50 is that they run counter-clockwise (looking from above). That is different from most other engines. Turning it backwards you have a good chance of damaging the water pump impeller.

I will try to not let my vast previous experience with other engines cloud my judgement.

Taking off the flywheel is easy. Remove the 4 bolts in the center of the flywheel and lift it off. You will need to immobilize the flywheel to get them out. I've used a pry bar across the bolts to hold it while I break them loose. If you do it that way keep them in until all of them are broken loose.

Pulling it off is easy. It's not a taper lock or woodruff key so you don't need a puller. There is a locating dowel on the underside. It might stay in the flywheel flange, it might stay in the crankshaft, it might fall out altogether. Just keep an eye on it so you can make sure it's there when you put it back together.

Cool. Will watch for that. It's only fourteen feet to the lagoon bed, and the seaweed hasn't bloomed yet.

Putting the flywheel back on is even easier. Just make sure that the dowel engages the flywheel and the crankshaft. Torque to 48 ft lbs. If you don't have a torque wrench, make them "good'n tight". That's between "pretty snug" and "real tight").

I plan to bring a torque wrench.

The only thing I remember being under the flywheel is the timing belt, a tensioner, and a couple of coils. One is for the ignition and one is for the alternator. Both of them are wrapped in a cloth-like material. If they have started to unwrap that might be the noise you are hearing. I horribly overheated a BF40 once and made the alternator coil come unwrapped.

I will check for wear and fraying.

If I was going to guess, I'd say you might have a timing belt tensioner that is too loose or wearing out. If that is the case you should strongly consider replacing your timing belt at the same time.

Is that the little wheel? Should I check the tension that?

It's not hard to replace a timing belt but it has to be done right. If it comes to it I'll post instructions and you can decide if you want to do it. Under no circumstances should you rotate the flywheel or the camshaft while the timing belt is off.

Cool. I'll save that for another weekend.

[Be Free]

Yes, the timing belt is the big one with teeth that goes under the flywheel and around the cam sprocket at the rear of the engine.

An interference engine means that the piston and the valves can "interfere" with one another if they are not timed properly. The timing belt is turned by the crankshaft and in turn the belt will turn the camshaft. When the crankshaft (pistons) are in time with the cam shaft (valves) the valves will only be open when the piston is down and the piston will only be all the way up when the valves are closed. When a piston comes into contact with a valve the engine makes very expensive noises.

Fixing the damage this causes is beyond the average home mechanic's skill. I have caused those expensive noises, proving I'm sometimes careless. On the other hand I fixed the damage, proving I was too poor to pay -- I mean above average in my mechanic skills.

If either of the coils is coming unwrapped it should be obvious. You may be able to trim the loose material (watch out for small wires) or glue it back into place.

Yes, the tensioner is a small wheel that pushes against the side of the timing belt. It has an adjuster (I think I remember a cap over the adjuster). If it is at the end of its ability to take up the slack then your belt is too stretched. You may get real lucky and just find that the adjuster has loosened and the tensioner not really doing anything.

Once you get the flywheel off it should be obvious what's making the noise.

[OverEasy]

Fixing the damage this causes is beyond the average home mechanic's skill. I have caused those expensive noises, proving I'm sometimes careless. On the other hand I fixed the damage, proving I was too poor to pay -- I mean above average in my mechanic skills.