Another Cracked Starter Boss - Mercruiser 350

Good day all! Complete noob here, and very new to boating.

'03 Mercruiser 350 Mag MPI Bravo III - 0M6XXXXX

Outboard starter boss cracked - thumbnail shape up through the counter-bore, right at the beginning of the threads. I would like to build a bracket & try it as an option before having to buy a new block.

Would like some feedback from those that have tried this route.

Thanks in advance.

Re: Another Cracked Starter Boss - Mercruiser 350

Ayuh,.... Welcome Aboard,.... I've seen it, but ain't tried it,...

Re: Another Cracked Starter Boss - Mercruiser 350

Okay folks, it has been a while but I wanted to post an update to this post. I decided to proceed with the bracket option, mainly because I decided I had absolutely nothing to loose: If this option didn't work, I would need a new block. If I did nothing, I would need a new block. If, however, this option did work... I just wouldn't need a new block as soon - Hah!

Here is a picture of the cracked starter boss. Note that the crack was really only up through the countersink, and did not protrude into the threads.

Cracked Starter Boss


It is a two piece bracket design: One piece that bolts onto the forward end of the starter, and another piece that bolts onto the bell housing.

Bell Housing Bracket


I replaced the bolts that held the starter together with m6 threaded rods to allow enough length to bolt on the bracket.

Starter Bracket


Entire Assembly


Bell Housing Bracket Installed


Starter Bracket Installed


I got everything installed this past weekend, and so far, it works like a dream. Of course from now on, it's one of my pre-operational inspections to put a wrench on all the nuts just to make sure everything is nice & snug.

Re: Another Cracked Starter Boss - Mercruiser 350

Had exactly the same thing on a V6 block a few years ago. Found a website that had very useful instructions on cast iron welding. Ground the crack out to a Vee, then used a MIG with a reasonably high current setting to just put in a 2 or 3 second zap. Left it for 10 minutes to cool down and did it again. Took a while, but the weld ended up very nice, almost couldn't see it when I finished, and it's been running fine for a few years now.

Chris......

Re: Another Cracked Starter Boss - Mercruiser 350

achris,

I did some initial inquiries about cast iron welding to a few local welders, and they all seemed to cringe. But that's good to know and will keep that in mind if this rig fails.

Were you able to do that without pulling the engine? I've got a Chappy 260 Signature, and it is TIGHT back in there. But after having done this, I don't think it would be too bad.

-walt

Re: Another Cracked Starter Boss - Mercruiser 350

I did pull the engine, but for other reasons. Never really seen a 'mechanic friendly' boat yet... They always seem to want to bury the engine as far back and as low as they can... :facepalm:.... I guess boat builders are like lawyers and politicians... something we can never get rid of...

Re: Another Cracked Starter Boss - Mercruiser 350

I realize I am getting into this too late for you, and you have made up quite a bracket! It is a bit of overkill - but better too much than not enough I suppose.

I had a pick up truck years ago that had a similar crack. Chevy actually makes a bracket just for that issue. It bolts onto the back of the starter and then the block. Very much like you see on a Mercruiser 3 liter. Here's a pic of it in place:

Re: Another Cracked Starter Boss - Mercruiser 350

Hey Fishermark,

Agreed, it probably is way overbuilt. But this boat had/has me paranoid now, so I'll err on the side of being (way) overly cautious.

You know, I saw the bracket type you show on ebay & elsewhere. And it looked like it was a perfect fit, or could easily be modified by drilling another hole if necessary. I guess, again, I was afraid it wouldn't provide the support needed to prevent the boss from breaking completely. And I didn't want to find that out by the wife & I having to hitch another ride from TowBoatUS. No offense intended to the TowboatUS folks at all, mind you!