Timing Problem GM305 Way off but runs great

[PitchFork]

I have a 1994 GM305 with a TB IV on it. I have had it 3 years and has always ran fine except for a slight hesitation / bog when I went to full throttle from 2,300 RPM. I checked the timing on the trailer on muffs and the timing mark was about an inch before the timing mark plate. So I adjusted the timing so it hit right on 8? BTDC and it idled fine. I took it out on the water and it warmed up fine in neutral. Once I got it out of the no wake zone I tried to get on plane quickly and it backfired out of the flame arrestor and sputtered. It did not stall.

I adjusted the timing back to where it was and the boat ran fine with a little bog when going from 2,300ish RPM to full throttle. So I adjusted the timing again back some more. Tested again the boat ran like a bat out hell. It accelerated at all RPM's better than I ever remembered it did.

I verified I was using the number 1 cylinder. I hooked the timing light at the distributor on #1 wire. Is that correct or should it be down by the spark plug?

What concerns me is that the timing light lights up when the timing mark is 2" from the 12? BTDC mark.

Thanks in advanced,
PitchFork

 

[Don S]

Re: Timing Problem GM305 Way off but runs great

Did you check the advance timing to see if it was working correctly?

 

[captmello]

Re: Timing Problem GM305 Way off but runs great

Sounds to me like your Harm. Balancer has slipped. The Bog you feel is classic Q-jet hesitation when the secondaries open.

 

[PitchFork]

Re: Timing Problem GM305 Way off but runs great

Did you check the advance timing to see if it was working correctly?

No I have not checked to see if the timing mark moves closer to the timing plate when the RPMs are bought up to 2,500. I will check it next weekend. If the Harmonic Balancer has slipped I guess I will have to figure out how to get it back to where belongs.

 

[robjen1019]

Re: Timing Problem GM305 Way off but runs great

might check the slack on the timing chain too.

 

[Silvertip]

Re: Timing Problem GM305 Way off but runs great

You don't put a harmonic balancer "back where it belongs" if it slipped. You put it in the trash can because it's broken. It's like a spun hub on a prop. Install a new one.

 

[PitchFork]

Re: Timing Problem GM305 Way off but runs great

Anyone have a Part Number for the Harmonic Balancer / Crankcase Dampener? I have been unable to find the PN in Manual #17 or on the online website I usually find part numbers. Looks like the outside ring of the Harmonic Balancer has slipped which moved the timing mark out of whack. Think I could take it to NAPA to match up to Automotive One if compatible?

 

[Don S]

Re: Timing Problem GM305 Way off but runs great

Just an FYI, you will not find part numbers for anything in the Service manual, only service information. You can get the OEM part from any online site that sells OEM Mercruiser parts, they aren't something that the after market companies will duplicate.
They are also a standard GM part, so yes, NAPA will probably be able to get one if they don't have it on the shelf.

 

[PitchFork]

Re: Timing Problem GM305 Way off but runs great

Thanks Don I will search online sites that sell OEM Mercruiser parts tonight. If need be I will take the part to NAPA as a last resort.

 

[Bondo]

Re: Timing Problem GM305 Way off but runs great

If need be I will take the part to NAPA as a last resort.

Ayuh,... That should be step1,... Not your Last resort...
The balancer is strictly a Chevy part,... Nothing Marine about it,+ No need to pay the Mercruiser prices...

 

[180shabah]

Re: Timing Problem GM305 Way off but runs great

Agree with Bondo - do not pass go, head straight to NAPA. It's just rubber and steel, nothing special.

 

[PitchFork]

Re: Timing Problem GM305 Way off but runs great

Thanks guys I will be going to Napa today during my lunch break. I did about choke when I saw the Mecruiser prices for the HB $210+ and then I looked at one for a 90's GM 305 on the NAPA website $60. I definitely decided to stay away from eBay on this one as all that I looked at on eBay were well used ones or high dollar $190.

 

[180shabah]

Re: Timing Problem GM305 Way off but runs great

That price difference can buy alot of gas....

 

[PitchFork]

Re: Timing Problem GM305 Way off but runs great

Ok I believe I found the correct Dorman Number for the HB 594-012. It looks like the previous owner put on a 594-009 which the timing mark is farther away from the key-way than 594-012.

I found the TDC and marked it on the HB that is on the crankshaft. It turns out the new mark is 1.25" closer to the key-way than the original mark cut into the key-way.

Should I replace it with a new HB $50 or just use the new mark and check the timing off the new mark?

I am leaning towards putting the right part on it. If I do put a new one on do I need to drain the oil or just use the HB puller and pull the sucker off and install the new one?

Any thoughts on replacing or using the old one with new mark?

 

[Silvertip]

Re: Timing Problem GM305 Way off but runs great

No need to drain the oil. Pull it and replace. You could also just buy a timing tape, clean the HB find top dead center and install the timing tape so the zeros line up and away you go. Cost? A couple of bucks.

 

[captmello]

Re: Timing Problem GM305 Way off but runs great

Have a look at this thread.

http://forums.iboats.com/showthread.php?t=282764

As you can see I had a slipped balancer which I replaced a year or so ago. By remarking the balancer, there is always the possibility of it slipping more so I don't see how you can just remark and use. I guess you'd have to recheck your mark every time you set the timing to know for sure. Getting one of those timing mark tapes is a good idea so you can check the advance timing accurately. You'll need a puller as well if you decide to change it. I was able to borrow one. I would also recommend painting a new one as I did not and it developed a nice layer of surface rust almost immediately.

Hope this info helps.

 

[PitchFork]

Re: Timing Problem GM305 Way off but runs great

Well it turns out I am going to replace because when I was putting the pulley back on one of the three bolt holes stripped out and would not tighten. I will be heading to NAPA again. When I had NAPA pull the two balancers 594-009 and 594-012 the 594-012 had the timing mark where I found TDC last night which was just left of the key-way.

Thanks for all the help

 

[PitchFork]

Re: Timing Problem GM305 Way off but runs great

Update

HB replaced. It was simple as pie to replace. Autozone had the HB 594-012 and the puller and installer as loaners. Put it all back together while checking the compression of the cyclinders 130 to 145 PSI and putting the correct plugs in AC MR43T gapped at 0.035".

Now I am waiting for the rain to clear to check the timing and test drive the boat.

Thanks for all the help.

 

[Dshow]

Re: Timing Problem GM305 Way off but runs great

Just curious, does the HB bolt directly to the crank shaft? Were the threads that were stripped in the HB or the crank shaft? Also, had the original HB slipped or was it just off due to being the wrong part number?

Thanks

 

[PitchFork]

Re: Timing Problem GM305 Way off but runs great

Just curious, does the HB bolt directly to the crank shaft? Were the threads that were stripped in the HB or the crank shaft? Also, had the original HB slipped or was it just off due to being the wrong part number?

Thanks

The HB pressed directly onto the crank shaft with an insttaller tool from AutoZone and the stripped threads were on the old HB (one the pulley bolt holes012. Looks like the wrong HB was on it. The new HB has the timing mark 13? to the right if looking from the distributor were the old HB has the timing mark probably around 26? from key-way. Also the old HB looked like Dorman 594-009 which the differences from the part I put on Dorman 594-012 was the outer ring is a little thicker and the timing mark was a lot farther past 13? more like the old HB.