Marine Power 5.7 worn distributor gear

[twinturbostroker]

Has anyone else had this problem?

I've been chasing a strange ignition related gremlin for months now.

After procuring the DIACOM software to access the MEFI-5 ECM, the only issue I could locate after several hours of running and recording data for analysis was the Cam Advance Angle readings were low, 630-645 range.

Specifications call for 705 at 1000rpm.

I played with the distributor quite a bit and was unable to procure anything close to the 705 specification and after speaking with MP they had asked if the distributor had ever been out of the boat.

I'm original owner, so that answer was definitely a no.

So based on the information from my calls into MP, out comes the dizzy, and sure enough, here is what I discovered after only 262 hrs on the clock. The gear appears to have worn about .60" off of about 5 or 6 of the teeth, the remaining teeth don't appear to have any visible wear.

Disappointing for sure.

AND to add insult to injury, The AC Delco replacement gear (Amazon sourced 1-day delivery) broke a tooth off when attempting to replace the distributor. No undo force, just popped a corner of the tooth off while re-inserting the distributor into it's location.

So this time I opted to source a new replacement gear from NAPA and proceeded to show the NAPA counter guy the one that had chipped a tooth off, and his exact words "AC Delco is garbage". I advised that it was sourced from Amazon 1-day, in attempt to get the boat back up and running for the holiday. He said, if it was delivered in 1-day it was sourced from a local auto parts distributor and unlikely it was a counterfeit piece.

NAPA gear - $7.99 with retaining finger clip, thrust washer, and a roll pin.

AC Delco gear - $36, gear only.

New gear installed and after a few adjustments, viola, 704.9 cam advance angle at 1000 rpm.

Hopefully this is the end of this chapter, as I bought a new boat to use, not to work on.

[gumby]

The cam shaft is walking. The retainer is loose or something You probably didn't start having problems till 100-150 hours. The timing chain cover must come off. intake must come off new cam and lifters. That is a cast gear so the cam looks the same as the gear on the the distributor. Worm gears are tolerance sensitive. I have seen this before. It is the only fix. sorry
Watch Running it that metal is getting in the oil not good on bearings. You will get a few more hours out of it but if you don't fix the cam it will happen again.but the more you run it the more metal you put in the oil till you start Knocking then it is over when the rod comes out of the oil pan.

[twinturbostroker]

I’ll reach out to Marine Power to follow up, apparently this was common enough for them to advise on pulling the distributor and checking the gear.

The camshaft gear looked fine and only one side of the distributor gear had signs of wear.

[gumby]

You might want to run a bronze gear or ask about it. Scary they said just change the gear. Do your self a favor change the oil a couple of times this season.I would also put a old speaker magnet on the bottom of the oil pan FOREVER.(on the out side of corse)
I guess they could have had a bad run of gears. Is this what they lead you to believe? I would think there would be a bad spot on the cam you would have to turn the motor over twice to see all of the cam gear. Start on Top Dead Center timing marks go by once 180 out come back to TDC. Plugs out will make it a lot easier. By your post I think you got it back together. So just watch it. If it were mine I would put a few hours on (like 20) it and pull it again check it for any sign of ware. Go from there and like I said I would use a magnet Forever.

[KoolAid]

Very good advice Gumby!

[twinturbostroker]

Just got off the phone with Shawn at Marine Power and he said that they did have an issue with a bad batch of distributors and gears from GM, and stated in all cases they merely just replaced the dizzy and moved on. He referenced a few of them are now clocking in over 4000 hours in Alaska.

He has advised that cam walk is not an issue with this generation 5.7 as the motor has a thrust plate on the front cover which allows .02-.04 of end play.

I’ve already changed the oil and no signs of any metal in the pan, so it’s likely been caught by the filter.

The speaker magnet is a great idea, and will be implemented as a safeguard.

The hydraulic roller cam is steel and the distributor gear is melonized, if the cam gear has any signs of wear upon it the bronze gear won’t last but a few hours. (Been there done that, got the tee shirt).

I’m going to run it as recommended by Marine Power and after a little time pull the distributor to check and monitor for wear.

I’ve been chasing this gremlin for about 10-12 hours of run time and to think that I would need to pull the motor refresh the valvetrain (cam and roller lifters) on an engine with 262 hours is nauseating.

I’m going to run it and see, if the problem persists, it’s back to drawing board.

Who knows maybe there’s a new rig on the horizon, this certainly gives me cause to start shopping.

[UNSTUCK]

only one side of the distributor gear had signs of wear.

This is the really weird part. Usually distributor gears are softer than the cam gear so the wear is easy to replace. Each tooth on the dist. gear should look the same though. I wonder if you have something else wrong somewhere else? Maybe you have a sticking valve that is putting extra load on the cam and in turn the dist. gear in that one spot. You should be (maybe) able to see/feel that in a rougher running engine though.

[gumby]

I did say it in my first post worm gears are sensitive to tolerance. If they had a bad batch of gears that were ground out of speck then BAM you got it fixed.and that might be the case. All you can do is hope your filter dose its job. and keep an eye on it.