Marine: Boating, Sailing, PWC, GPS and Navigation - Timing a 454 ???

I have almost finished rebuilding the upper part of my motor. The risers and manifolds were replaced. The lifters and push rods were replaced. The heads were sent out and the valves were redone. Now I have everything back together and I have to set the timing. I know that you need to get it to top dead center and set the distributor.

The problem is I was told I had to use some sort of jumper wire to cut something out or i might damage the motor. Then I read in the service manual that the thunderbolt V (v8) needs a scanner used on the distributor when setting the timing. Later in the manual I read how to time the motor and it doesn't say anything about the scanner.
Can you guys help as I am ready to start the motor
1995 454 Merc V, not FI

The way I used to static time an engine after a rebuild or the distributor was out was take a spark plug and widen the gap real wide, like 1/4 inch and use a hose clamp and a piece of wire and strip the wire on 1 end and attach it to the outer part of the spark plug with the hose clamp and attach an alligator clip to the other end of wire to ground it to something like the block. Get your timing mark on your crackshaft on top dead center or even a little before that if you choose to try for the spec and make sure you are on compression stroke and not exhaust. This can be done while you have out the number 1 spark plug cram a rag or paper into the spark plug hole while you turn over the engine near top dead center. On exhaust stroke the rag or paper will puff out, but on compression stroke it will pop out even more. Then plug that test spark plug you just made into the number 1 wire and ground the other end. Next loosen the distributor hold down bolt just enough that you can turn the distributor and then turn the igintion key to the run position and while your timing mark is on top dead center on the compression stroke, turn your distributor untill the spark plug sparks. You may have to turn it quickly or search for it but when it sparks tighten down the distributor snug so it wont turn at that spot and install the plug. Start it up and then set it while running, but this should at least get you started. Remember to prime the oil pump!!! Tighten the distributor bolt. Good Luck.

I forgot that you said only the top half was redone. Maybe no need to prime the pump. As I remember all chevys point the number 1 on the cap right at the number 1 cylinder or that is how I always did it. If you didnt bump the engine or move the camshaft and where the distributor goes into the oil pump at the bottom then it should be close to firing. Did you remember to mark everything first?

A marine 454 is no different than an automotive 454 (it's the same monster) when it comes to setting timing. I always simply use a pencil in the spark plug hole to determine TDC while turning the engine over... (at it's highest point - you're at TDC - on the firing stroke) Then I set the distributor so that the rotor is at the number 1 cap post... and rough set my timing from there... If you can get it to fire - then you're 3/4ths of the way there....

Zster, how can you be sure you ain't on the exhaust stoke?

check the rockers, they will both be in the same position (closed).

Exactly right!

Also...I use a cheater bar on the crankshaft to turn the engine over by hand to find TDC... trying to bump with the starter is close to impossible....