Dial Indicator?

[Bill H]

I found some good tips doing a search, but will they work if the plug goes in at an angle relative to the piston?

[Raceman]

It won't be accurate unless the dial indicator shaft is perpendicular to the piston top. Whether it makes a singificant difference depends on how much the angle is. If you stop and think about it, if the dial indicator is at an angle, one of two things has to happen as the piston comes up............. either the point of the shaft has to slide on the piston, or it has to bend or distort the shaft.

I don't know what kind of motor you're working on but I useta have a dial indicator spark plug hole mount that was drilled at an angle to accurately find TDC on a Yamaha dirtbike with an angled hole. I would think that if there are outboards with an angled hole somebody would make a specialty type mount to hold the dial indicator dead straight.

[Bill H]

Thanks, Raceman. That is what I thought.

[Raceman]

Bill, I should've been paying more attention, but forgot you were asking about a 6 cyl stern drive in another thread. An easy way to find TDC is to make a positive stop that goes in the spark plug hole. This can be done by removing the middle from a spark plug and welding a piece of rod in it, or beating something that fits it tight in for that matter. Then you rotate the engine BY HAND in one direction until it hits the stop, and mark the balancer. Rotate it by hand all the way in the other direction until it hits the stop again, and mark the balancer again. Half way between these two marks is TDC.

[Bill H]

Thanks Raceman, that's how I'll do it.