Odd Timing Issue

[Haut Medoc]

Hi All....
It's been a long time.
Here goes:
I recently purchased a 1979 SeaRay SRV 30, with twin GM 350's (255HP).
Ran great on trial.
When I did some PM, like I do on everything I own, on the port side engine, (standard rotation), I could not see the timing mark when I put the timing light on it.
It sounds good & with a mirror, I was able to see the mark with a mirror on the nearly 6 o' clock position.
This would normally tell me that the wires are in the wrong position & that some other cylinder should show on the timing tab as I moved the tester connection from ignition wire to ignition wire, I thought one should be in the ball park, but no.
The closest I could get was to see the #2 past the timing mark, (ATDC) or at # 7 (BTDC) and basically right in the middle of both with either left me trying to retard, which made it run too slow & want to die or too fast which made it race.
The distributer is a billet type Pertronix.
I am much more familiar with Ford, but if I recall a GM dist. only goes in one of two ways on or 180 out.
I just can't figure out why I am basically 22 degrees off either way, right in the middle of either 2 or 7 lining up.
I'm missing something here & I don't know what.
The engine sounds good, but I really don't want to cruise it until I am satisfied it is timed correctly according to the mark & tab.
I tried bringing it to TDC and just can't get it to run using what would be normal procedure.
Brand new plugs were black after short use.
Any help appreciated....... Thanks!

 

[achris]

Rubber in the harmonic balancer slipped? (It happens)

 

[Eric 3.7LX Alpha 1]

Rubber in the harmonic balancer slipped? (It happens)

Good guess. That's easy enough to check with twins too.

 

[Scott Danforth]

you can stab a distributor in any way you want. however it only runs if you are on TDC of compression stroke of #1 and the rotor is pointing to the tower wired to the spark plug for cylinder #1

dont look at the mark on the damper to determine TDC, look at cylinder #1 to determine it. normally, with an assembled engine, I have used a piston stop that goes thru the spark plug hole and a degree wheel on the damper

piston stop tool

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regarding the damper ring. the rubber is good for about 15 years (sometimes they last a bit longer, sometimes they fail sooner). your boat is almost 43 years old. you most likely need a new damper

 

[Haut Medoc]

Hmmm....
I didn't know that was possible, but it does make perfect sense.
Scott, thanks for the link, looks like I can buy a balancer, degree wheel & a piston stop for $100 bucks or so.
How exactly does the piston stop actually work? I'm not familiar with it.
I never have timed anything other than using the standard method.
The engine compartment at the front is TIGHT, so it is nearly impossible to look & crank at the same time.
If I can time it once, I can get through the season without having to pull the damn thing off and I deal with it in the off season.
Appreciate all the feedback.....

 

[Scott Danforth]

Hmmm....
I didn't know that was possible, but it does make perfect sense.
Scott, thanks for the link, looks like I can buy a balancer, degree wheel & a piston stop for $100 bucks or so.
How exactly does the piston stop actually work? I'm not familiar with it.
I never have timed anything other than using the standard method.
The engine compartment at the front is TIGHT, so it is nearly impossible to look & crank at the same time.
If I can time it once, I can get through the season without having to pull the damn thing off and I deal with it in the off season.
Appreciate all the feedback.....

if you are buying a new balancer, you most likely will not need the degree wheel, however any good wrench should have one

piston stop tool usage -

for me: with harmonic damper puller - pull damper
use SBC crank turning socket (like this or similar) https://shop.advanceautoparts.com/p...um-fits-chevy-small-block-v8-67491/10286488-p

bolt degree wheel to socket. make a pointer with a piece of coat hanger

pull all the plugs, install piston stop tool. by hand using a short handle ratchet in the above socket (do not use the starter to do this) turn the motor until you come to the piston stop. write down the number where the pointer is on the degree wheel.

turn the motor the opposite way until you come to the piston stop. write down the number where the pointer is on the degree wheel.

TDC will be in between those two numbers. so now remove the piston stop tool and turn the motor until the pointer is exactly between the two now motor is at TDC

 

[Haut Medoc]

Great advice!...Thanks!

 

[Haut Medoc]

Yup....
Harmonic balancer was slipping.
Put a new one on & timing was in the ball park hitting right at TDC.
A twist of the wrist & all better.
I should to return to posting, since I do know a thing or two.
Appreciate everyone's help with this...... Thanks!