MCM 175 Timing Question

Hello,

I am new to iBoats. Nice forum here. I have a 1987 Mercruiser with an Alpha 1drive. The engine is a MCM 175 (4.3L V6)

The question I have is: On my engine, I do not have a timing scale. I have a pointer coming off the block and a line on the balancer (no scale). I have timed the engine to this mark with the idle set at 650 RPM. Right to specs. The engine idles and runs fine except for one problem. I am not able to reach max RPM under load in the water. I can only reach 3600 RPM. I have a feeling that I do not have the base timing advanced enough. But then why this set up? Why have the pointer and line if the line itself is not 8 Degrees BTDC? You really don't need to know where TDC is when setting ignition timing. So wouldn't you say that the line on the balancer is 8 Deg. BTDC? Otherwise, how would you time it?

If anyone is familiar with this set up, please let me know.
Thanks!

Re: MCM 175 Timing Question

Do you have a picture of your pointer on the timing cover? The 87 models all had the timing tab with a bunch of marks.
The newer Vortec engines with a composite timing cover had a single cast in line in the cover that matched up with the line in the dampner. That is usually TDC, on what the timing is supposed to be.

Re: MCM 175 Timing Question

Don,

I could get a picture over the T-day holiday for you to see. But if that line on the balancer is TDC. Wouldn't the engine idle poorly if the spark was coming at TDC? Right now the engine idles real smooth and runs up to 3600 RPM smoothly. I also checked to make sure the throttle plate butterfly valves were opened all the way at full throttle. They were.

Thanks!

Re: MCM 175 Timing Question

I have never seen the groove in any dampner be anything but 0?. The pointer may be setup for your timing, but it's not OEM for that year.

Re: MCM 175 Timing Question

Ayuh,.. I can't imagine what you're lookin' at Either....

If it's timed Tdc, it'll idle, 'n run fine with No power.... Like it's doin'....

Maybe a digital timing light, 'n dial it into 6? or so....

Really need the Pictures.....

Re: MCM 175 Timing Question

Thanks guys,

I am going to the local junkyard to pick up a 4.3L -5.7L timing scale. The old owner must have not put the original back on the engine.

Re: MCM 175 Timing Question

You can save yourself a lot of problems by just buying a timing tab. most auto parts stores sell them.

Re: MCM 175 Timing Question

Don,

I just found that out for myself. I went to the junkyard only to find out that 4.3L to 5.7L enigines timing tabs were either spot welded on the timing cover or riveted to the block. So I went to Autozone. $7.00 and I got one.

Thanks for the help.