[BMC 1.8] Start motor machine gun crash sound (issue identified, need advice)

[thematt]

Hey folks, me again. I'm having all sorts of fun this season getting my old engine ready for adventures. Got around to investigating the intermittent start motor crash sound. It was super loud. I found that each side of the fly wheel that aligns with the compression strokes has some messed up teeth (see image). I desperately do not want to replace the fly wheel if possible.

 

Question 1 and 2. Can I take a dremel and gently remove the burrs? Are these teeth too far gone?

 

Question 3. Looking at the wear patterns it doesn't look like the start motor gear is full engaging with the fly wheel. I'm still a new to this all, would you all agree?

 

Bonus points questions. It also appears I have a rear main seal leak (see photo - endoscopes are cool). Plus evidenced from oily start motor when I pulled it. It's not terrible, loses maybe a quart over 100 hours I believe. Is this a 'wait and see' sorta issue, or a fix asap? Anyone have luck with oil leak stop products or are they just snake oil (no pun intended)?

 

As always thank you all for your time!

 

[Tony Brooks]

1. Yes.

 

1a. What about the teeth on the pinion, is the pinion getting the full throw, all but up against the stop/drive end housing? Some starters have an adjustable pivot to ensure it does.

 

Apply six volts (if you can, but difficult with modern batteries) and use jump leads to connect neg to the starter cane and the pos .to the "energise" (from ign. switch) terminal. Then see where the pinion stops. If there is a significant gap post a photo of both SIDES of the starter drive end so I can see if you have an adjustment.

 

2. No

 

3. Answered in 1 above.

 

4. I can't make head nor tail from the endoscope images of the seal, and wonder how you got it between the flywheel and engine end plate. I can't see any black oil stains.

 

If the drip tray/bilge fills with water, any oil on the surface is likely to leak into the flywheel housing and get thrown into the starter, so oil in the starter does not necessarily mean a rear main oil seal leak. It could be as above or a leak from the gearbox input shaft seal. It is the starter that is the major item that is likely to eventually suffer from such leaks on the vast majority of marine engines. It is likely to gum everything up with brush dust and posisbly caause  ashort circuit in the brush end of the starter.  

[thematt]

 

48 minutes ago, Tony Brooks said:

1. Yes.

 

1a. What about the teeth on the pinion, is the pinion getting the full throw, all but up against the stop/drive end housing? Some starters have an adjustable pivot to ensure it does.

 

Apply six volts (if you can, but difficult with modern batteries) and use jump leads to connect neg to the starter cane and the pos .to the "energise" (from ign. switch) terminal. Then see where the pinion stops. If there is a significant gap post a photo of both SIDES of the starter drive end so I can see if you have an adjustment.

 

2. No

 

3. Answered in 1 above.

 

4. I can't make head nor tail from the endoscope images of the seal, and wonder how you got it between the flywheel and engine end plate. I can't see any black oil stains.

 

If the drip tray/bilge fills with water, any oil on the surface is likely to leak into the flywheel housing and get thrown into the starter, so oil in the starter does not necessarily mean a rear main oil seal leak. It could be as above or a leak from the gearbox input shaft seal. It is the starter that is the major item that is likely to eventually suffer from such leaks on the vast majority of marine engines. It is likely to gum everything up with brush dust and posisbly caause  ashort circuit in the brush end of the starter.  

Thanks so much for the quick and detailed reply. There's a starter motor shop near by. I'll take the motor there tomorrow afternoon now that I have half an idea of what might be the issue. Thank you! I'm very glad I'm not looking for a new flywheel. I'll be sure to follow up on the resultion.

 

Edit: to answer at least some of your question before tomorrow. See attached photo of pinion.

 

Re. 4. - the endoscope is ~1/2 diameter of my pinky finger. So it fits around the back of the fly wheel. The top have of the backplate is dry. In the last photo you can see a dry patch surrounded by oil. Right under the seal is the 3rd photo with oil everywhere. The endoscope came back oily as well. I have half a mind to try something like 'at 205 stop leak', but the other half really doesn't want to make anything worse.

Edited May 8 by thematt
answer a question better.

[Tony Brooks]

The question about oil leak stopping additives. I tried them on a leaky Montego (BL) engine, and it did not work. I think they are supposed to swell the seals, but in my experience swollen rubber type compounds tend to go soft as well, not what you want with a lip seal unless it is just for a quick sale. 

 

I think you would be better off:

 

1. the oil level is correct and not over filled.

 

2.  The angle of the engine is within accepted limits (too steep an angle and even with the correct amount of oil in the sump it will be over full at the back).

 

3. Ensure the crankcase breather system is clear, and you can easily blow through it.

 

After that accept it is a gearbox and flywheel off job so best left until later on if you want to go cruising or run the engine now.

 

 

[thematt]

1 hour ago, Tony Brooks said:

The question about oil leak stopping additives. I tried them on a leaky Montego (BL) engine, and it did not work. I think they are supposed to swell the seals, but in my experience swollen rubber type compounds tend to go soft as well, not what you want with a lip seal unless it is just for a quick sale. 

 

I think you would be better off:

 

1. the oil level is correct and not over filled.

 

2.  The angle of the engine is within accepted limits (too steep an angle and even with the correct amount of oil in the sump it will be over full at the back).

 

3. Ensure the crankcase breather system is clear, and you can easily blow through it.

 

After that accept it is a gearbox and flywheel off job so best left until later on if you want to go cruising or run the engine now.

 

 

1. It's correct. Just replaced. Oil level exactly at Max line. Perhaps it'll leak down a bit and find it's happy spot?

2. Engine is at ~15 degrees. Not much I can do about that with the v drive etc in place to make the shaft exit the stern tube correctly.

3.checked and cleaned. New oil cap installed as well.

 

Looks like it's an accept and wait for the winter job. The last thing I want to do is to use something that will make the leak worse.

 

Thank you Tony!

[thematt]

22 hours ago, Tony Brooks said:

1. Yes.

 

1a. What about the teeth on the pinion, is the pinion getting the full throw, all but up against the stop/drive end housing? Some starters have an adjustable pivot to ensure it does.

 

Apply six volts (if you can, but difficult with modern batteries) and use jump leads to connect neg to the starter cane and the pos .to the "energise" (from ign. switch) terminal. Then see where the pinion stops. If there is a significant gap post a photo of both SIDES of the starter drive end so I can see if you have an adjustment.

 

2. No

 

3. Answered in 1 above.

 

4. I can't make head nor tail from the endoscope images of the seal, and wonder how you got it between the flywheel and engine end plate. I can't see any black oil stains.

 

If the drip tray/bilge fills with water, any oil on the surface is likely to leak into the flywheel housing and get thrown into the starter, so oil in the starter does not necessarily mean a rear main oil seal leak. It could be as above or a leak from the gearbox input shaft seal. It is the starter that is the major item that is likely to eventually suffer from such leaks on the vast majority of marine engines. It is likely to gum everything up with brush dust and posisbly caause  ashort circuit in the brush end of the starter.  

Back from the shop. The gentleman working threw the motor in a vice and ran though the tests. My current start motor is operating perfectly. I brought along the nasty one that came with my surplus engine. It was very bad. The start motor professional reckons that it was that motor that did the damage. Further, for any the come across this in the future, he said the marks on the fly wheel in the first picture are 'totally normal' and not and indication of a pinion gear not fully engaging the teeth.

 

I tidied up the teeth with some carful dremeling and now have a reference on the crank shaft pully on what locations to start the motor in. The pinion gear is still in perfectly good condition as well. I'm lucky.

 

I also learned, that at least for my particular starter, it's a marine starter and there's a seal between the motor and pinion unlike standard automotive starters. Basically no worry about oil intrusion from a leaky rear main seal. Just the mess to deal with.