Are Mercury Outboard starter 10 tooth drive gears all the same?

I just had the starter rebuilt for my '89 Mercury 115 HP outboard. I intentionally had the starter rebuilt as opposed to buying a replacement because I wanted to make sure I had the same 10 tooth drive gear and the replacements seem to have gone to an 8 tooth drive. Even the Mercury replacement drive gear for my starter is an 8 tooth drive. I installed the rebuilt starter and now when I try to start the motor the drive gear rises as it should and spins as fast as I would think it should. The problem is that it does not mesh with the flywheel. I've had the starter on and off a few times before and after the rebuild and it looks like it only goes in one way. One of the mechanics at the local marina suggested that I check the voltage drop at the starter which I will be doing as soon as I am sure (again) that my battery is fully charged. I don't think that a poor connection is the problem because I would think that if the starter spins fast enough for the drive gear to move up to the flywheel, it would engage the flywheel and then crank slowly or stall if there wasn't enough current. But this does not happen. The drive gear spins and seems to bump into the flywheel and continues to spin rubbing the bottom of the flywheel.The only thing I can think of causing this would be the wrong size 10 tooth drive gear, but I don't know if Mercury makes more than one size. The local marina was helpful in that they looked up and pulled the drive gear for my motor from their stock to compare with what I have now, but they only stock the 8 tooth gear which seems to be what Mercury has standardized on for my starter. I am trying to give the shop that rebuilt my starter the benefit of the doubt when they say that they rebuilt my starter, but I don't know if they swapped mine with another that looked the same but has a slightly different drive gear. After my battery is topped off I'll go back to check voltage drops, but I don't want to waste any more time if I have the wrong starter or drive gear - so if Mercury only makes one size 10 tooth drive gear I'll continue troubleshooting, but I can't help but to think that I have a bad or the incorrect rebuilt starter. With the weekend getting closer I want to be able to order any parts I might need.
Thanks in advance for any input...

I attached photos showing the problem I am having with the rebuilt starter. The first photo (top view) shows how much I had to loosen the starter mounting bolts in order to back off the drive gear to allow it to mesh with the flywheel teeth (I circled the gap).The side view of the starter drive gear shows how the teeth of the flywheel appear to rub the rim of the drive gear preventing the drive from meshing with the flywheel.

Since I know of no adjustment for the starter (shims?) the problem as I see it, is that the drive gear is the wrong one. I went back to the shop that did the rebuild and he showed me what he said was the original drive gear. It looks like the same size as the one that does not work. This makes no sense since the starter did mesh with the flywheel before it was rebuilt. I am going to check to make sure the flywheel is not damaged (somehow out of round?) but I don't think it is. I am thinking of buying the 8 tooth drive gear and trying it if it looks like a smaller diameter than the 10 tooth gear. If anyone has any suggestions as to what could be the problem it would be appreciated.

Also note: I did check the voltage drop across the starter while I turned the key and starter was spinning. Voltage was approx. 12.7 V. Battery voltage was 13.5....

Somehow you have the wrong pinion. Did you count the teeth on the one that was supposedly your old one?

Then there's this: Merc used two different tooth profiles for pinion gears; coarse and fine. The coarse teeth are bigger and won't mesh properly with a fine tooth flywheel. So even if the tooth count on the pinion is correct, the teeth can be the wrong ones.


Arrrgh!

Jeff

PS: I went through this exercise when upgrading my Mark 78 to a modern starter. Drove me batty for a while.

Thanks a lot Jeff for your input. What you describe sounds like what I have. I just don't get how the original and the new pinion look the same. I got back the original from the shop so I can compare a little closer. I counted the teeth on the pinion gear before I took it to the shop so that I would avoid this BS (good and bad were both 10). I'm going out to do some more checking. I'll let you know what I find. The other thing I am thinking of trying is the 8 tooth pinion, but I read good and bad opinions about using the 8 pin on a motor that had a 10 pin original.

If that 8 tooth will fit the starter shaft AND engage the flywheel correctly, it will do a fine job of starting the motor.

Jeff

Update - I planned on buying an 8 tooth pinion gear and trying it with the rebuilt starter before the weekend. However, while at the marina and before I paid the $61.00 for the for a new pinion I measured the i.d. of the pinion to make sure it would fit. Comparing it to my original 10 tooth pinion, I found it to be approx. 0.7 mm smaller than the original. So I didn't buy it, but I took the original pinion back to the rebuild shop and had him put original on the rebuilt starter. I figured it did spin the new flywheel before the rebuild so maybe it will still work.

Note - Original problem with original starter was that after replacing the flywheel, the motor would crank, pinion would engage and start motor. Engine would die after a few second because of lack of gas I suppose (cold start). Then if I tried to restart the motor the starter would crank very slow if (at all) and not start. Recharged battery, same scenario. Waited 8 hours without recharging battery, same scenario. I ultimately felt around the pinion and it felt real hot so I figured the starter armature was bad.

Here are some pics of the new pinion and my original flywheel, the original pinion with the original flywheel and the original pinion with the new flywheel. It looks like the pinions are the same with the exception of the original has some wear so is not as pointy as the new one. If the original pinion ends up working, all I can surmise is that the fact that it is worn and not as pointy allows it to engage the new flywheel.
I'll be able to try it tomorrow...I can't wait.

Me too!

Good luck.

Jeff

Thanks Jeff.

I tried the starter with the pinion that the guy that rebuilt the starter said was original - exact same symptom. Pinion spins and pops up and appears to (and sounds like) it hits the bottom of the flywheel then drops down. I have a couple of ideas of what might have happen, both related to mix ups during the rebuild and me not getting the original pinion back. This would explain why the original pinion no longer engages the new flywheel.

But there is an outside chance that the flywheel I recently put in is slightly bigger (1/8" to 3/16") than my original flywheel. But if that was the case then the original starter pinion would never have engaged the new flywheel and started the motor - which it did before the rebuild... But to again give the starter rebuild guy the benefit of the doubt I'm going to go out and try to check the circumference of the flywheel teeth on the new flywheel and compare with the original. I already counted teeth - both 94. If there is a difference I might put the old flywheel back just to see if the said original pinion engages old flywheel. I tend to think it will not, but I might have to check.

Also, the local service marina has actually been really helpful in that they spent some time discussing my problem and trying to figure out what is going on. The owner was out yesterday, but he heard of the problem when I called their parts dept. today asking for a very specific part number for a pinion gear. He asked if I could bring the starter in and discuss the problem. He put starter in a vise did some checking. He's the one that suggested that I pull the replacement flywheel and verify to original, then put original back on motor and see if starter pinion engages original flywheel. Seems like a good idea to get to the bottom of things and could prove one way or the other if I have original pinion back.

Update - I checked / compared the circumference of my original flywheel with the recently installed flywheel by taking a 1/2" wide nylon strap and wrapping it around the original flywheel teeth and marking the strap. I then took the strap to the recently installed flywheel and wrapped the strap around it's teeth and checked where the line matched up. To the best that I can tell it looks like both flywheels have the same circumference. I can't think of another way to check circumference without using a caliper to check diameter - which I don't have. Otherwise I could still remove the flywheel and hold it up to original to compare. I'm trying to avoid pulling the flywheel because it was somewhat of a PITA to hold the flywheel and tighten up to 120 ft pounds.

I'm attaching a picture of the pinion gear that I think I might need. The resolution isn't the best, but if you zoom in you can see an extra groove in the top ring that I don't see in either of the other pinions that I currently have. If anyone has any experience or comments about this particular pinion gear it is appreciated.

Fastjeff - Could this be one of the pinions you mentioned in one of your replies?

I didn't do a good job of explaining why I think that pinion I attached in last update might work. That is one of the part numbers I found from Merc for a 10 tooth for my 115HP. Also I meant to say there looks like a deeper cut into one side of all the teeth that I don't see in either pinon that I have or any other that I've seen pictures of. You have to zoom in to really see it.
regards....

Is there any way you could borrow a starter for an similar motor and compare it yours, or take yours along and match it up?

Otherwise, you'll have to keep trying various pinions to get something to work.

Jeff

That's the wrong drive...you need a # 13310.

Dumb question - but thought I'd add it in the pot. I believe your starter is similar to mine. If so my starter motor is isolated from the block / clamp with a rubber? isolation ring. Perhaps they have different OD rings? If the the od of the bushing is smaller the clamp can be tightened fully...... JMHO

Fastbullet - Thanksfor the info. I looked up that part number and it looks like it's for an 8 tooth pinion. I know the starter had a 10 tooth pinion when I brought it to the repair shop. That's the mystery. The other thing is that when I was at the marina parts dept. I was going to buy the 8 tooth pinion for my motor. I cly smaller hecked the id an it was slight

and Re: Are Mercury Outboard starter 10 tooth drive gears all the same?

Keyboard problem...continued -

I measured id of 8 tooth and was smaller so I did not buy it.

Fastjeff - I went to a different motor rebuild shop yesterday in search of a pinion that would work. These guys were great. They gave me a used 8 tooth pinion to take home and see if it would work - turned out that it would not fit on armature shaft so I couldn't try. They suggested I slightly enlarge the hole ib their used pinion (on a bench press to be accurate) and put on my starter and at least see if the 8 tooth would properly mesh with my flywheel. I will try that later today. Thennn...as I was in my car getting ready to leave one of the guys came running out with a rusty old starter that he said was donated to them. It looks like mine but has an 8 tooth He said I could take that with me as well to at least install in my motor as see if it matches up (I won't try to start it of course). As I said, these guys were great. I only with I knew of them before I took my motor to the other shop.

Canufixit - Not a dumb question. I considered that earlier and checked part numbers for the top and bottom rubber ring. Both the same.Also I had my starter with me at the local marina and they looked at it and said the rubber looks correct.

I have to run some errands but I will be able try matching up the donated starter and 8 tooth pinion later today. I still might swap back the original flywheel to see how things match up but I'm still avoiding that because I think I will have same results.

Thanks again to everyone for input.

Good Luck!

Canufixit - Thanks...

Update: I bought a clamp that was long and wide enough to reach around my flywheels and I used it to compare the diameter of the two. They appear to both be the same. I already checked the circumference yesterday with a nylon strap and got the same measurement and counted the number of teeth on both - both 94. I have no reason to think my replacement flywheel is different than the original, so the original pinion gear should work with new flywheel.

It turned out that the salvage starter the guy from the the repair shop gave me was longer than the original starter so I couldn't try it for size comparison of the 8 tooth pinion. I also tried to enlarge the hole on the used 8 tooth pinion but couldn't do it with the 1/2" drill bit I have. I might see if I can pick up something to enlarge the hole.

I still think I have the incorrect 10 tooth pinion. I know the parts breakdown for my motor ('89 Merc 115 hp 4 cyl. serial OD01xxxxx) shows the 8 tooth, but my starter had the 10 tooth. It looks like the armatures for the 8 and 10 tooth starters are slightly different diameters so the common 8 and 10s are not interchangeable. As I mentioned earlier, the Merc 10 tooth that I attached a pic of has the extra notch cut into it which might be what I need. Or else, my motor has a different problem that threw the alignment out of what. It doesn't appear to have a loose crank and it turns OK without binding. So I'm going to see if I can research the parts history of my motor and see if I can find anything.

Gosh! Solve this one and you'll be a candidate for the Mechanic of the Year award.

Jeff

Update - Spent the weekend looking at parts breakdowns of different Merc motors to see if I could make sense out of my starter/outboard combo. I already new that my ob called for an 8 tooth pinion, I was trying to find what might have been in there before I took the starter to be rebuilt. Found a few potential part numbers that were made for different motors, but no pics of the gears to do an actual comparison.


So on Monday, I found a guy that works on old outboards and cars out of his pole barn. We looked for either a 10 tooth pinion that was different than the one I had (perhaps deeper cut grooves in gear) or an 8 tooth starter for my motor. Found neither.


So my next trip was going to be to a local marina that also works on older outboards. On my way there, I reconsidered another possible cause of my starter mixup. Late last fall I had to have my boat picked up by one of the local marinas to winterize and store for the winter. When I called this summer to pick it up they said that they couldn't get it started in the fall and did not winterize. They said they still could not get it started, so I told them to just bring it to my house and I will take care of it. That is when the flywheel/starter saga began. The motor would crank when I got it from them, but it would start cranking slowly after a short time so I would have to recharge the battery shortly after troubleshooting would begin (but the starter did engage the flywheel and the motor cranked). That was when I found the flywheel with the loose and cracked magnets. I replaced the flywheel, and tried to start it again. This is when the motor would crank and start one time - then crank very slowly on subsequent tries to start. I already replaced battery and fully charged it with same results, so I pulled the starter and started it with jumper cables. The starter did spin several times without issue on the cables so I thought I had a starter that failed under load. I looked into buying a replacement starter on line, but reading the reviews I found that some people said they received 8 tooth starters when they should have 10 tooth, as well as other issues. With that, I decided to have my started rebuilt, so I would not run into any compatibility issues (this is also why I made sure I counted the teeth om my original starter and knew it had 10 teeth). After I put in the rebuilt starter was the first time I had the issue with the starter not engaging the flywheel. The reason I mention this additional history is because I got to thinking that maybe the marina that stored my boat and troubleshot the no start problem might have swapped out my original original starter and not put
the correct one back. I called this marina and told them what was going on. The owner didn't know what the mechanic did, but he was willing to swap a rebuilt 8 tooth with my rebuilt 10 tooth. I put the 8 tooth starter in yesterday and it cranks like a charm. Now I have what looks like a fuel issue (possibly because it wasn't winterized last year) but at least this makes sense.

All ya needed was the 8 tooth part# I posted....glad ya got it cranking!!!!

Faztbullet – I couldn't use the pinion with that part number (13310) because it had a smaller diameter hole than the shaft that I had on the starter that was on my motor. That's what made this difficult to figure out. I still can't say positively if the wrong starter was swapped in by the mechanic at the marina when he was troubleshooting the no start problem, or the guy that rebuilt my starter replaced a 10 tooth deep or narrow cut pinion (if there is such a thing) with a standard cut pinion.

All I know is somehow my 115 hp had a starter with a 10 tooth pinion installed on it when I started troubleshooting the no start problem this summer. The 10 tooth pinion meshed with my flywheel enough to start the motor before and after I replaced the flywheel. After the flywheel was replaced (because it had loose and broken magnets) the motor still cranked and started .But it appeared that I had a starter that failed under load – although it could have been that the starter was binding because it was a 10 tooth pinion with a flywheel that called for 8 tooth pinion (I don't know and did not consider it because I didn't know that my starter might have been replaced last fall or early this spring??). After I replaced my starter with the rebuilt one the rebuilt starter did not meshed with the flywheel. This led to the original question I started this post with - “[FONT=Arial, Veranda, sans-serif]Are Mercury Outboard starter 10 tooth drive gears all the same?” [/FONT][FONT=Arial, Veranda, sans-serif][/FONT][FONT=Arial, Veranda, sans-serif]I still can't say positively one way or the other because I did find part numbers for starters for smaller hp outboards that had 10 tooth pinion gears that might be different than the one I had. But that no longer matters to me because I had the wrong starter on my outboard, and I have the correct working one on it now.[/FONT]


[FONT=Arial, Veranda, sans-serif]Thanks again to everyone that offered advice and suggestions.[/FONT]


[FONT=Arial, Veranda, sans-serif]Regards....[/FONT]

I'm putting you down for the Mechanic of the Year award!

Jeff

Thanks for the compliment Jeff. Pretty crazy problem huh?

The funny (or not so funny) thing is, if I would have simply went on Amazon and ordered the starter that it has listed for my motor, I would have received an 8 tooth starter and it would have probably worked for my motor and I would have saved about $80 (I paid $140 for the rebuild). But again, after seeing that Amazon had the 8 tooth listed and knowing I had the 10 tooth installed in my motor and not knowing what I would have gotten as far as quality from Amazon, I felt safer with the rebuild.

But at least I got to learn more than I ever wanted to know about Mercury starters and made some contacts in my local marine service arena as well as this forum.

Regards...