Blown Main Fuse

[BlueSkies]

About 6 weeks ago, as I tried to start the Rotax 912ULS in my Tecnam P2004 Bravo, the prop made maybe a half-rotation (maybe more, I wasn't counting at the time) and stopped. All power was gone. The main power fuse (80 amp) had blown. I thought that maybe I had "double-clutched" the starter, causing an extra load on the starter. The fuse was replaced, and I have made several engine starts since. 2 days ago, same thing happened-1 or 2 blade turns and everything died. Blown fuse again.

Again, the fuse was replaced, and the engine started without a hiccup. I did a start-up yesterday with no problem.The engine has 450 hours on it.

I have a (feeble) working theory that the prop position at the time of start-up may be a factor, causing a bigger load on the starter in getting the mass moving when at a certain position. But why now, after 4 years of no issues? Possibly the gearbox is requiring more torque? I'm not an engine guy, so I do not have any real clue.

One instance, I would write off as statistical happenstance. But twice may be the start of a trend.
Thanks in advance for any insights on this.

[3Dreaming]

Does the engine turn like normal when turned by hand? Had you pulled the engine through prior to starting? There are any number of possibilities from a bad starter motor, a shorted wire in the starter circuit, to a hydro locked cylinder.

I had a customer once who right after a condition inspection went to start his airplane and the voltage dropped to around 5v when he turned the key. It wound up being the wire for the soft start module had rubbed through the insulation and grounded itself. He doesn't have a main fuse, but if he did I suspect it would have blown.

[BlueSkies]

I do burp the engine prior the the first start of the day; it usually takes 6-10 full turns. Ihave not noticed any changes in this.

I haven't yet keyed on watching the volt meter during the process.

I do not have the soft start modules, but the modules do have some age on them.

[3Dreaming]

The issue with the soft start was not with the module itself, but the installation. If anyplace in the starter circuit wiring has insolation that is worn through and touching ground will likely blow the fuse while cranking the engine.