I don't know if I have vortec heads or not. Whatever they would have put on a 350 MPI Horizon in 2003. The plugs I have are the NGK Laser Iridiums and I think they came gapped at .060 and I'm sure I checked them as well. I have a gap tool that should make it easy to get them to .038. Current plan is new cap/rotor/wires. Check phasing. Re-gap plugs. The unfortunate part is that where I boat is 2 hours away and when I go, I'm there for at least the weekend. Hopefully this solves my problems. Last weekend was a bit miserable being stuck on an island in 35-40mph NE winds and not knowing 100% if the boat was going to run well to get back to the mainland. lol.

Vortec heads used from approx 1996 and up. Easy to identify. Intake is held down with 8 bolts (4 per cyl head) at a straight down angle. Earlier heads had 12 bolts (6 per head)) at angles holding intake to the heads. Those used MR43T plugs.

1st pic Vortec (note straight up and down bolt holes. Their are none in middle positions unlike earlier heads)

https://cimg0.ibsrv.net/gimg/www.off...bea8e5283.jpeg





2nd pic earlier sbc heads


https://cimg8.ibsrv.net/gimg/www.off...02b365f1c.jpeg

Playing around with this, I discovered that it is quite a bit off. So much so, that I don't think the housing will rotate far enough without interference. Does this mean that its off a tooth?

https://cimg4.ibsrv.net/gimg/www.off...42721a2b46.jpg
https://cimg6.ibsrv.net/gimg/www.off...389eceab77.jpg

If turning dist and there is interference, dist is prob off a tooth. Prob someone who didn’t move oil pump pushrod a hair (need long flat blade screwdiver) and just dropped it back in.

You ever put a chevy dist back in ? If so, this is piece of cake.

You know the history on this ?

I've never done this. My experience is on smaller imports etc. The history that I know of is that the PO had the same issues I'm having. Hard start etc. One time it actually just stalled. He found the distributor loose. He rotated it to the point that it ran and left it. I don't know if he may have removed it to try and tinker or not. Or if his mechanic may have. I know he had trouble finding people to work on his boat and took it upon himself a lot. Some of his work was good, some was less so.

Lol.

Any ways. Dist is easy. Loosen clamp first and see if it turns enough. Recheck alignment when you tighten clamp. It can move a few degrees as the dist and cam gear are helical.

I'll give it a shot. just looking at it, it looks like the housing will hit the intake manifold before it gets to the exact right location. I bet I can get it close. One fun thing would be if I had to remove it. I may or may not have enough room to get it out of the boat. Perhaps I could pull it up, rotate it, drop it, and turn the engine by hand to line up the oil pump?

No no no. I’ll give you my cell in a pm. I mumble so put your good ears on. Leave engine at tdc. It’s easy.

if the phasing is off it will run like crap and cut out i use an old cap cut open to get it right

On this, you don't need too. There is a little pointer if you will on the distr that the rotor will point too. It's about an inch or so up from where his rotor is in that pic. And by his pic, his dampener is at TDC.