Help!!!!!!!!!!!!!!!!!

[CAPTKEV85]

hi im new to this forum. im kevin. i have a 1977 mercruiser 470 3.7 litre 4cylinder. i just rebuilt the motor and for some reason my distributor keeps jumping the timing gear. any ideas. she idles great once i go to rev it up the gear on the distributor jumps or something.

 

[Haut Medoc]

Re: Help!!!!!!!!!!!!!!!!!

Welcome to iboats....
What do you mean jumps?....
You are going to have to be more specific about your symptom....
Timing chains & distributers don't just jump.....​

 

[45Auto]

Re: Help!!!!!!!!!!!!!!!!!

Hard to see how a distributor gear could "jump" unless the hold-down bolt wasn't in it......

 

[CAPTKEV85]

Re: Help!!!!!!!!!!!!!!!!!

Ok Heres How It Went I Just Rebuilt The Motor. I Set The Dist At Tdc (top Dead Center) Aiming To A Bolt That I Marked When I Pulled It Out. I Started The Boat Ran Fine. Then I Went To Rev The Engine And It Started Popping And Sluggish. So I Shut Her Down And Turned Her Back To Tdc. I Pull The Cap Off And Shes Facing 180 Degress The Other Way. The Bolt To Hold The Dist Down Is Tight I Have Oil Presseure And The Piston Are Not Hitting The Valves. So I Put The Dist Back To Were It Was Supposed To Be Aiming At The Bolt. Start It Up And It Idles Fine Once I Rev It Again I Pops. So I Pop The Cap Again And Its Off By 90 Degrees. Its Drivin Me Nuts. Someone Told Me The The Dist Gear Pin Might Of Broke. But I Ran Out Of Ideas

 

[Haut Medoc]

Re: Help!!!!!!!!!!!!!!!!!

Ok Heres How It Went I Just Rebuilt The Motor. I Set The Dist At Tdc (top Dead Center) Aiming To A Bolt That I Marked When I Pulled It Out. I Started The Boat Ran Fine. Then I Went To Rev The Engine And It Started Popping And Sluggish.
Did you reset the timing @ idle before you revved the engine?

So I Shut Her Down And Turned Her Back To Tdc. I Pull The Cap Off And Shes Facing 180 Degress The Other Way.
Just becase the timing mark is at TDC does not mean it is in the #1 firing position......


The Bolt To Hold The Dist Down Is Tight I Have Oil Presseure And The Piston Are Not Hitting The Valves. So I Put The Dist Back To Were It Was Supposed To Be Aiming At The Bolt. Start It Up And It Idles Fine Once I Rev It Again I Pops. So I Pop The Cap Again And Its Off By 90 Degrees. Its Drivin Me Nuts. Someone Told Me The The Dist Gear Pin Might Of Broke. But I Ran Out Of Ideas

You need to find #1 TDC & install the distributer with the rotor pointing at the #1 lead.....
If the engine will run, you need to set the timing to spec.....
You also need to make sure you have the ignition wires in the proper sequence, an engine can idle with two reversed wires, but will not rev...
Are all of the wires good?.....
There is no way an engine will run with the distributer out 180* or 90* for that matter.....
& I doubt very much the gear is loose....
You are missing something basic....

 

[CAPTKEV85]

Re: Help!!!!!!!!!!!!!!!!!

Im Gonna Check Wires Tonight But I Have Them In The Right Order But Ill Try Again

 

[Haut Medoc]

Re: Help!!!!!!!!!!!!!!!!!

One other thing to check is to verify advance.....​

 

[CAPTKEV85]

Re: Help!!!!!!!!!!!!!!!!!

Springs On The Centrifigul Advance Are Lubed And Working. Im Gonna Put A New Cap And Rotor In And Reset Everything And Try It Again If Its Still Acting Up Im Gonna Pull The Timing Cover

 

[AZSenza]

Re: Help!!!!!!!!!!!!!!!!!

Check the oil pump and oil pump drive shaft. make SURE the roll pin that holds the cam gear on the distributor is not sheared, I would suggest actually taking the gear off and reinstalling it with a new pin just to be sure. This is something very few people can diagnose since the pin wont fall out. it just shears and stops again as it hits interfearance 180* out. Just a thought...

 

[CAPTKEV85]

Re: Help!!!!!!!!!!!!!!!!!

I Was Planning On Removing The Dist To Check That. I Was Told By One Person The There Is An Alignment Tool For The Dist. But I Asked Mercruiser And They Said No.

 

[Fishermark]

Re: Help!!!!!!!!!!!!!!!!!

An Alignment Tool For The Dist.

I too would suggest pulling the distributor and checking the pin that holds the gear in place - the one driven by the camshaft. Other than that, I have no idea.

If Its Still Acting Up Im Gonna Pull The Timing Cover

Taking off the timing cover isn't going to be easy as you would have to remove the oil pan to take it off... Plus, if your timing gear was that bad I would think you would have noticed when you rebuilt the motor.

 

[Fishermark]

Re: Help!!!!!!!!!!!!!!!!!

Actually, when I wrote the above, I was thinking of the 120 /140 Mercruiser engine. After rereading your post, I am not familiar with the one you have.

 

[CAPTKEV85]

Re: Help!!!!!!!!!!!!!!!!!

Yeah The Timing Cover Comes Off Easy On The 470 Merc. But Im Gonna Check This Pin

 

[krisnowicki]

Re: Help!!!!!!!!!!!!!!!!!

Well if it was facing the other direction and the timing mark ios at TDC that means that it is on the exhaust stroke of the #1 cylinder. Which is normal... have you checked the compression since the incident?

 

[Bt Doctur]

Re: Help!!!!!!!!!!!!!!!!!

Yeah The Timing Cover Comes Off Easy On The 470 Merc. But Im Gonna Check This Pin

I dont think so,
crank pully, stator, circulating impeller, coil, hoses, dropping the pan
double check the pin for the gear, set #1 at TDC and install with rotor facing #1 wire in cap. firing order 1-3-4-2


rear 4 3 2 1 front

 

[whywhyzed]

Re: Help!!!!!!!!!!!!!!!!!

....

 

[Coors]

Re: Help!!!!!!!!!!!!!!!!!

Yeah, I lean that way- drag racing a sb mopar; you buy that pin (hardened), and install, as they break often.
Just a thought.

 

[CAPTKEV85]

Re: Help!!!!!!!!!!!!!!!!!

I Replaced The Pin Because There Was Play In The Gear Now She Is Tight. But I Just Had The Carb Redone And I Think Thats The Problem When I Throttle Up Now. Nothing Wrong With Timing. Factory Spec Is 8 Degrees. Set It To That Firing Order Correct And All Plugs Are Firing. Oil Pressure 40psi. But It Just Occured To Me That The Carb Is The Prob. They Probably Rebuilt It To The Wrong Spec Or Something. She Loads Up At 1000 Rpm And I Rev Her Up And It Just Gargles. So Im Sending The Carb Back Today And I Should Have It Tomorrow

 

[CAPTKEV85]

Re: Help!!!!!!!!!!!!!!!!!

Problem Solved!!!! Timing Chain Was Off A Tooth I Must Have Check It Ten Times When I Put It On. But I Must Of Missed It. Now She Runs Great. Thank God To Dished Top Pistons Saved The Valves. Thanks For All The Help Guys

 

[Haut Medoc]

Re: Help!!!!!!!!!!!!!!!!!

Well, that would do it......
Glad you got it solved....​