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pmagistro · 05-01-2017, 16:30

My mis-adventures with the cantankerous SB12 in my '78 Bristol 29.9 Tanager continue. Yesterday morning we motored out of Southport into 8 foot seas and a 15kt headwind. Slow going. My crew went green and her breakfast went over the side, along with any ability to help. We thought about turning back, but after talking with some other boats continued south, beating as best we could. Before long, the wind shifted, the seas died down, and we enjoyed a spectacular 24 hour sail at 6kts under a double reefed main and partially furled genoa.

Arrived at Charleston approximately 2pm today. On entering the harbor, we discovered that our cranky old diesel refused to start. So for the second time on this journey, we came into a marina under sail. (Somebody remind me to buy

towing insurance tomorrow?)

I originally thought it was a battery issue (running all night, lights, no engine, maybe depleted the bank?) But I have a house and starting battery, and the house battery was reading 12.5v (enough in the past to start no problem) and the starting battery 13.1v. Neither battery would start the engine. So I tore into the engine. I think what happened is that seawater flooded the cylinder (because there was salt water sprayed around in the engine compartment, and I took the air intake off and there was salt water in the valve). I was able to close the raw water intake, disassemble the exhaust, turn it over by hand and expel the water, but the engine simply would not start. Thinking maybe that I had burned out the starter, I removed the alternator belt....and voila! She started right up!

I've been playing with the alternator belt for a bit now. If I put it on, at all, the engine simply will not start. Without, no problem.

So. WTF? I suppose we don't -need- the alternator....my solar system should keep us charged up adequately, but I just don't understand. Were these problems related? Do I need to have the alternator rebuilt? Or is something else going on that I don't even understand? What do you think???

Captain Bill · 05-01-2017, 16:36

Interesting problem. Can you turn the alternator and water pump pulleys by hand with the belt off?

pmagistro · 05-01-2017, 17:02

I can turn the alternator pulley by hand. I don't think there is a water pump pulley. Only one belt on the flywheel.

jimbunyard · 05-01-2017, 17:40

How many pulleys are on the engine?

motion30 · 05-01-2017, 18:03

You have a water pump

pmagistro · 05-01-2017, 18:27

Quote:

Originally Posted by motion30

You have a water pump

I do, but I think it runs off the camshaft? There is one pulley on the engine with two grooves but only one belt that leads to the alternator.

Steven UK · 05-01-2017, 20:33

If the cranking speed is marginal the alternator load could push it under the required minimum. I'm going to let others go through the options because in my industry I would use starter fluid but I wouldn't want you to blow up the boat, that won't help at all.

jimbunyard · 05-01-2017, 20:45

Quote:

Originally Posted by pmagistro

My mis-adventures with the cantankerous SB12 in my '78 Bristol 29.9 Tanager continue. Yesterday morning we motored out of Southport into 8 foot seas and a 15kt headwind. Slow going. My crew went green and her breakfast went over the side, along with any ability to help. We thought about turning back, but after talking with some other boats continued south, beating as best we could. Before long, the wind shifted, the seas died down, and we enjoyed a spectacular 24 hour sail at 6kts under a double reefed main and partially furled genoa.

Arrived at Charleston approximately 2pm today. On entering the harbor, we discovered that our cranky old diesel refused to start. So for the second time on this journey, we came into a marina under sail. (Somebody remind me to buy

towing insurance tomorrow?)

I originally thought it was a battery issue (running all night, lights, no engine, maybe depleted the bank?) But I have a house and starting battery, and the house battery was reading 12.5v (enough in the past to start no problem) and the starting battery 13.1v. Neither battery would start the engine. So I tore into the engine. I think what happened is that seawater flooded the cylinder (because there was salt water sprayed around in the engine compartment, and I took the air intake off and there was salt water in the valve). I was able to close the raw water intake, disassemble the exhaust, turn it over by hand and expel the water, but the engine simply would not start. Thinking maybe that I had burned out the starter, I removed the alternator belt....and voila! She started right up!

I've been playing with the alternator belt for a bit now. If I put it on, at all, the engine simply will not start. Without, no problem.

So. WTF? I suppose we don't -need- the alternator....my solar system should keep us charged up adequately, but I just don't understand. Were these problems related? Do I need to have the alternator rebuilt? Or is something else going on that I don't even understand? What do you think???

Seems that you need to determine if it's the tension the alternator belt is putting on the engine or the load that the alternator is putting on the engine that's keeping it from starting. Try disconnecting the alternator (field and charging wires) and see if she starts with the belt, at normal tension, on. If it starts then, as unlikely as it seems, it must be the electrical load that's preventing starting.

If it doesn't start, then it's either something mechanically wrong with the alternator (maybe a seriously worn alternator brg that locks the alternator up when side tension is put on it, though that should be noisy as hell), or something wrong with the engine, like seriously worn crank bearings, though that too should be noisy and evident from extremely low oil pressure.

Of course if your raw water pump is gear-driven, and the engine doesn't have a circulation pump (my reason far asking how many pulleys you have) then you can just leave the belt off and skimp on juice.

But it's an interesting problem, and maybe this will give you a bump so someone with more experience with these engines will provide some clarity.

Barney21 · 06-01-2017, 15:31

Now that is a weird one.
One sentence in your note has me confused.

"I've been playing with the alternator belt for a bit now. If I put it on, at all, the engine simply will not start. Without, no problem.":

I dont quite follow how you can "put the the belt on at all" how do you manage to put it only partly? Or am I not understanding?
One thing you can try , but be careful pull the belt off or loosen the belt so it will not turn the alternator pulley start the engine, when the engine is running adjust the Alternator so the pulley starts to turn if that stops the engine ,either the engine has lost all power or the alternater bearings and maybe the whole thing and needs to go where the crew deposited breakfast.
I will be interested in this result

pmagistro · 06-01-2017, 15:33

Quote:

Originally Posted by Barney21

Now that is a weird one.
One sentence in your note has me confused.

"I've been playing with the alternator belt for a bit now. If I put it on, at all, the engine simply will not start. Without, no problem.":

I dont quite follow how you can "put the the belt on at all" how do you manage to put it only partly? Or am I not understanding?
One thing you can try , but be careful pull the belt off or loosen the belt so it will not turn the alternator pulley start the engine, when the engine is running adjust the Alternator so the pulley starts to turn if that stops the engine ,either the engine has lost all power or the alternater bearings and maybe the whole thing and needs to go where the crew deposited breakfast.
I will be interested in this result

I thought perhaps I had it too tight, so I loosened it a bit. If I tighten it to the point it actually spins the alternator pulley, the engine will not start. Doing more diagnostics tonight. Will update results as I learn...

Stu Jackson · 06-01-2017, 15:46

Excuse me for not going into your profile or trying to find out more from your previous (but un-linked) postings, but what engine do you have?

**Madehn** · 06-01-2017, 16:39

unless your battery bank is really marginal, my vote is for the alternator hav:ing a bad bearing that locks it up with any side tension. I guess you could have a REALLY weak starter also-- when you say it does not start, does it turn over and just not fire or does it refuse to turn over? Also can you see a noticable drop in turn over speed with the belt on and off? please let us know what the answer is! good luck

topmast · 06-01-2017, 17:41

With no answer to the problem. Slack the belt, start engine .tighten belt to recharge Carefully. If no noise or grinding look to marginal batteries ,too worn rings Meanwhile ,is there a valve at the transom exhaust to keep back flow down?

pmagistro · 08-01-2017, 14:00

Quote:

Originally Posted by topmast

With no answer to the problem. Slack the belt, start engine .tighten belt to recharge Carefully. If no noise or grinding look to marginal batteries ,too worn rings Meanwhile ,is there a valve at the transom exhaust to keep back flow down?

No valve at the transom. Frankly I am not super comfortable tightening the belt with the engine running....not much clearance in there and I don't want to catch myself up in that belt! I want to disconnect the load per the earlier suggestion and see....but we are in the wilds of the SC/GA ICW and think I am going to wait until St Augustine to mess around. There at least I can have the alternator rebuilt if it has in fact gone bad.