Not if the system has a wet muffler. Any wet muffler can fill with water if the engine is cranked too long. The water can then intrude into the cylinders.
I blew a fuse!
- Thread starter Tally Ho
- Start date
My exhaust exit is above the waterline. But I believe you can create a hydro lock situation, even if the exhaust is above the waterline.
Greg
My 2 cylinder 15 HP Yanmar 2QM15 has reliably cranked and started while the start circuit is protected by a 250 Amp Blue Seas MEGA fuse. My start battery is a group 24 and the cable size is 1/0 throughout. The start battery is just a few inches in front of the engine so the cable length could not be any shorter. Last year had a hydrolock event and the fuse blew while attempting to start. Note that the motor was completely locked and failed to turn over causing the fuse to blow. As far as the starter motor was concerned this was a true "locked rotor" event. The battery at the time was fully charged and in good condition. After clearing the hydrolock problem and replacing the fuse all went back to normal with no damage to the starter or battery. I only report this here as a real world experience for a properly sized fuse doing its job of protecting the circuit and its components.
I'm not sure you heard that right ... Calder basically said the fuse isn't required (for reasons that are related to the auto industry) but he recommends using a fuse in boating because our batteries are typically located where longer cable runs are required and voltage drop can be a factor. One thing that I picked-up on that never sunk in to me before is that it is the one location where you can exceed the ampacity charts when selecting a fuse, so grossly over-fusing the cable is acceptable.
I suppose that you could do what you propose, but I don't know why you would do it. If you have a long run from battery to starter, I don't know why you would want to leave that cable un-fused. It may be advantageous if you have a much shorter run from battery to starter than from switch to starter, I suppose. I'm not sure why you would want to monkey around with your cable plan.
I would still change the 2 AWG to 1/0 at least, if it's not too inconvenient.
What he is saying is that all banks on a boat should have over current protection, including starting banks.
The ABYC does not require a fuse on a cranking conductor/ battery so you can't really 'over-size' a fuse for the wire because one is not even required...
In a dead short the fuse will blow even if over sized for the wire..
Fuse your start battery with a fuse large enough to avoid nuisance trips..
If your engine is too large to fuse put the wire in a protective conduit or loom/sleeve..
The ABYC does not require a fuse on a cranking conductor/ battery so you can't really 'over-size' a fuse for the wire because one is not even required...
In a dead short the fuse will blow even if over sized for the wire..
Fuse your start battery with a fuse large enough to avoid nuisance trips..
If your engine is too large to fuse put the wire in a protective conduit or loom/sleeve..
I don’t have a dedicated start battery…
So, if I fuse the bank, it has to be a big enough fuse to not blow when I start the engine.
I assume a 200-300 amp fuse (I ordered a 225 amp for now), is better than no fuse when there is only 1 bank.
My other thought was to run a separate wire to the starter (it could be fused with a 300 amp fuse) and another wire to the panel (fused with a smaller fuse…maybe 100 amp).
The runs are not long. Maybe 6 feet from battery to panel, from panel to engine starter is maybe 9 feet.
Greg
I don't think @Benny17441 is correct. Most installations I am familiar with have a rather high loop of exhaust hose, and your raw water pump can fill the water-lift muffler and hose enough that water will run back into the cylinders with open exhaust valves.
If you crank for more than 15 seconds or so you should drain the muffler before proceeding. Then you can just leave the petcock open until you get it started, letting the water run into the bilge to be pumped overboard by the bilge pump. Don't forget to close the petcock once you're started, though!
Just to close this thread (at least for now), I put the MRBF fuse holder and a 225 amp fuse back on the battery bank today and after bending the sails on, took Tally Ho out to stretch her legs and shake out the sails. Engine started fine at the dock, no fuses blown.
Only about 40 F today on Lake Michigan, and very breezy.
So, I feel more confident about the fusing now.
I will order a spare as @MikeHoncho suggested.
Greg
Only about 40 F today on Lake Michigan, and very breezy.
So, I feel more confident about the fusing now.
I will order a spare as @MikeHoncho suggested.
Greg