1999 Mariner Magnum III Starter motor

Our 1999 Mariner 150 Magnum III has been bullet proof except...over the years it occasionally and randomly won't engage the starter motor. This is a little disconcerting when 30 - 40 miles away from launch point. There is no sound when key is turned to start. Zero click. This has only happened three times but, by happy happenstance, I have had mechanics on board twice when this has happened so I had great help and good knowledge and traced the power to the solenoid and through the soleoid to the starter...but it remains a mystery to all as to why this happens and why it seems to corrects itself once we get it started....and why it occurs so randomly and at such wide intervals....sometimes a year and 40+ starts apart. In the two instances with mechanics on board, after spending an hour scratching our heads, we were able to pull start the motor with the emergency rope....once started and then shut off....the starter worked fine for the rest of the year. It has never happened at the dock on a cold start...and we live in Northern Idaho and use the boat during quite cold (below freezing temps) often in the late fall and early spring months. The last time it happened, after pulling off the cowling, I rotated the starter just a bit...and then it started as though nothing was wrong...again and started like new the rest of the day (fishing). The last time I took both the starter and solenoid off and had them checked and both check out fine. So..I decided to purchase aand install both a new solenoid and starter and have our local Electrical Spe******t shop rebuild the old starter and keep it for a spare.

So...here is my question. I went online to purchase a new starter from Mercury and I the Marine site noted Merc OEM starter was no longer available and listed several replacement options....which are really, really inexpensive as compared to the Merc OEM starter. I am skeptical...but are these replacement starters durable and reliable? Anyone have any experience with them?

Sounds like the nuetral start switch needs adjusting.

After removing, cleaning and reinstalling battery cables, the neutral start switch position/wiring was the second thing we checked the first time this happened. and I checked it at the "bench" when we got home too....and have looked at it each subsequent time it has happened. It is correctly positioned. Power appeared to be getting to the starter through the solenoid....which confused us and confuses me to this day as it indicates there is a mysterious and minor fault in the starter motor itself that only surfaces when the stars align and cosmic forces frown. When bench tested w/proper equipment at home, everything checks out. If it happened more often i could probably run down the cause! So not sure if I am happy or not about this happening so rarely. At any rate....I plan to install a new solenoid and starter so would like some advice on what starter to purchase....particularly the ones less than $100 bucks. Has any on this forum any information on them?

It has been a while....but I wanted to follow up on this in case solving my issue would help someone else. I took the motor to a long established, well respected business specializing in electrical issues. They informed me they could only diagnose the problem while it was occurring. I asked them to rebuild the starter....and they said they would not "because we can not get parts for marine starters.". So I asked them to take it apart and inspect it for me....which they declined. I suppose it is a money issue or something. At any rate, I went home and took the starter off the motor and took it apart to inspect it myself. To those who haven't taken a starter apart (as I had not) to inspect it I would encourage you to do so. It was easy and simple. Upon inspection I could not see anything wrong. In fact, the starter looked new, except for some dust from the brushes wearing. There are four brushes and they were all still good. Two are grounded to the starter frame and two are positive and wire to the positive wire coming into the starter. I decided to clean up the little bit of dust around the brushes and, lo and behold, one of the negative wires was completely loose and the other negative wire was easily movable. I tightened them, reassembled the starter and figure that was the problem. I had discussed this problem with a friend who is an engineer so when I explained to him what I had found he said that the starter was probably only getting half the power and it should also turn over faster. He was right. It turns the motor over twice as fast now. Much easier cold winter starts (I have had the boat out five times with no problems). Judging from how the motor is turning over, and how long the mystery dead starter issues have occurred, the one totally loose wire has been that way since I purchased the boat in 2003. So....if you are having starter issues...first lesson....it is really simple to take the starter off...take it apart and inspect it before going to the expense of purchasing a new starter.