Starter engaging with one bolt installed, spins but does not engage when both bolts are installed

[Auftiuk]

I have mercruiser 3.0. I had a broken starter bolt which I extracted and replaced with mercruiser original starter bolt. Since then my starter is not working while installed on the engine.

It works fine when bench tested and as long as I install one of the 2 bolts. I have to leave the bolt loose for it to engage the flywheel. As soon as I insert the second bolt or try to tighten the first one, I hear a whining (spinning) sound without engaging the fly wheel. I have tested the solenoid, the connections, voltage drop test, ground and + all check out.

Has anybody had similar issues? Any pointers will be appreciated.

 

[ScottinAZ]

I have mercruiser 3.0. I had a broken starter bolt which I extracted and replaced with mercruiser original starter bolt. Since then my starter is not working while installed on the engine.

It works fine when bench tested and as long as I install one of the 2 bolts. I have to leave the bolt loose for it to engage the flywheel. As soon as I insert the second bolt or try to tighten the first one, I hear a whining (spinning) sound without engaging the fly wheel. I have tested the solenoid, the connections, voltage drop test, ground and + all check out.

Has anybody had similar issues? Any pointers will be appreciated.

I am assuming that you re-installed the same starter? may want to check the clearance between the bendix shaft and the flywheel, IIRC on Chevy auto's its around 1/8 inch (check this number, Its been a while since I had to check one). If you do not have enough clearance, the gear will not pop out and you will have issues. If its too tight, there are shims for this available at nearly any auto parts store. If its too LOOSE, you may have to replace the starter, as the housing could (but not likely) be warped from having the other bolt broken. If it were me, I would be finding the root cause of the old starter bolt breaking off. Could be simple like a backfire when starting, or it could be a gross misalignment somewhere.

 

[achris]

I have mercruiser 3.0....

Mercury started using the 3 litre in about 1970, and they're still using them .. can we at least have a year for your engine (not boat, engine), or better still the engine serial number....

Thanks,

Chris....

 

[Auftiuk]

Engine number M008995

 

[Auftiuk]

Engine number M008995

 

[Auftiuk]

I used the original starter and also tried another starter I have. Both had the same issue.

 

[achris]

Any history we should know about? How did the first bolt get broken?

Chris..

 

[ScottinAZ]

sounds like its definitely time to check the starter pinion (AKA bendix) gear to flywheel clearance, and also the condition of the ring gear.

 

[Auftiuk]

I have had at least 3 bolts breaking in the last 2 years. I extracted and replaced them without problem. I have no good explanation of why they keep breaking. I was getting fed up with it.

 

[ScottinAZ]

if you keep breaking the starter bolts, there is definitely something wrong between the starter and flywheel. You need to find out why this keeps happening.

 

[Auftiuk]

Invaderscott…. How do you go about looking for the cause? Any suggestions? Much appreciated.

 

[ScottinAZ]

the situation you have SOUNDS like the starter is too tight to the flywheel. You need to check the clearance between the pinion (bendix) and the flywheel. I would also be checking the condition of the ring gear on the flywheel, as a too tight condition over time will eat the teeth on both. I would also be checking to see if there was any kind of runout on the flywheel causing tight spots. One other cause, although unlikely is over or under tightening the bolts. Any of these can cause the starter to flex on the bolts causing them to work harden over time and break. If you find the clearance is too tight, as I stated in my first post, there are shims available to get you to the proper clearance. Normal clearance from what I can find online is about .030-.060 between the bendix gear and the flywheel. Back in the day, we used to measure between the pinion shaft and flywheel for the clearance, but I cannot remember that number, nor can I find it online anywhere at the moment. IIRC it was around 1/8 inch or so. this number is MUCH easier to check, as the bendix wants to automatically retract into the nose housing making the other measurement much harder to get.

note that too loose is better (not by much, but still better) than too tight. Perhaps if you cannot get anything into the flywheel housing to check the clearance, get the shim pack for the starter (any auto parts house has Chevy starter shims), and throw about .010 in there and see if the situation improves. Note that this is NOT the preferred method, but in the absence of a better way, it will work

 

[Auftiuk]

the situation you have SOUNDS like the starter is too tight to the flywheel. You need to check the clearance between the pinion (bendix) and the flywheel. I would also be checking the condition of the ring gear on the flywheel, as a too tight condition over time will eat the teeth on both. I would also be checking to see if there was any kind of runout on the flywheel causing tight spots. One other cause, although unlikely is over or under tightening the bolts. Any of these can cause the starter to flex on the bolts causing them to work harden over time and break. If you find the clearance is too tight, as I stated in my first post, there are shims available to get you to the proper clearance. Normal clearance from what I can find online is about .030-.060 between the bendix gear and the flywheel. Back in the day, we used to measure between the pinion shaft and flywheel for the clearance, but I cannot remember that number, nor can I find it online anywhere at the moment. IIRC it was around 1/8 inch or so. this number is MUCH easier to check, as the bendix wants to automatically retract into the nose housing making the other measurement much harder to get.

note that too loose is better (not by much, but still better) than too tight. Perhaps if you cannot get anything into the flywheel housing to check the clearance, get the shim pack for the starter (any auto parts house has Chevy starter shims), and throw about .010 in there and see if the situation improves. Note that this is NOT the preferred method, but in the absence of a better way, it will work

Thank you INvaderS, you are the best. Will take your advise. And update tou

 

[kenny nunez]

There should be support bracket on the brush end of the starter, either with a 1/4” 20 stud on the upper field frame through bolt or a 5/16” stud that attaches cast iron bracket on the outer frame to another stud in the engine block if your starter is the early Delco Type.

 

[Auftiuk]

Kenny…. My starter is not a Delco. Thx though.

 

[Auftiuk]

One thing I forgot to mention. The oil pan was removed and replaced due to oil leak a month or two back. Has anyone heard of the oil pan interfering with the mating of the starter to the engine?

 

[ScottinAZ]

unless you started breaking starter bolts after the pan was done, you are barking up the wrong tree.... The only possible way that the pan or gasket could interfere with the starter would be to be massively displaced, and that would likely have not fixed the oil leak.

What Kenny is talking about is the style of the starter on the engine, not necessarily the brand of the starter. The original design of the starter was by AC Delco, OEM supplier for Chevrolet, who supplied the engine to the marinizer, in this case Mercruiser. Your starter should be of this design, just "marinized" for boat use. all exploded drawings I have found up to present show a version of a Delco starter on the 3.0 engines. You should have a small bracket on the back of the starter that goes to the block around where the oil filter boss is. (that general area at least). If this is missing it will add stress to the two other bolts, but I must admit, I never used these in my cars when I had them with this style starter over MANY tens of thousands of miles of use. Not that it should be deleted, but I dont think its the root cause of your starter woes.

 

[Auftiuk]

Invader…. Thank you again. In fact I ordered the brace 2 days ago. I did not have it before.

As you can obviously see, I am an enthusiast but don’t know much. I am soaking what you are sharing. Thank you all for the input.

 

[nola mike]

Invader…. Thank you again. In fact I ordered the brace 2 days ago. I did not have it before.

As you can obviously see, I am an enthusiast but don’t know much. I am soaking what you are sharing. Thank you all for the input.

The PMGR starter doesn't use the brace on the vee engines, not sure about the 3.0

 

[ScottinAZ]

The PMGR starter doesn't use the brace on the vee engines, not sure about the 3.0

Just for stuff and giggles, I checked the exploded diagrams before my last post. there is a rear bracket shown on all iterations of the 3.0 up to present on "another" website that has the exploded diagrams on it for easy ordering. Couple of different styles, but all show a rear brace/bracket