Intermittent rpms between 2800 and 3800

"Finally spent a week in the 1

"Finally spent a week in the 1000 islands using my 1979 PennYan 26 ft with twin 318s.

During a cold start at the beginning of the day the starboard engine worked fine and then other times usually when it was warm it would go back to not running over 3000 rpms. I could definately notice a vibration like I lost a cylinder but then the next day it would be back to normal.

I plan to:
Change gas filters (mine are unique in that they have smaller diameter threads on the connections to the filter canisters)

Change the water separator filters again.

Go to a set of 440 spark plug wires to eliminate going thru the exhaust manifolds.

Change the ECU module, since I don't have a spare.

All in all the boat was a blast, especially when both engines were running well.

Any comments would be a big help.

PS: Any suggestions on do's and don'ts when restuffing the shaft boxes?

Thanks for the help,
Jeff"

"Jeff, what do you mean when y

"Jeff, what do you mean when you say "Go to a set of 440 spark plug wires to eliminate going thru the exhaust manifolds". Is going thru the manifolds an issue?

Tweed"

"Tweed,
I have read a few tim

"Tweed,
I have read a few times on this site that 440 wire sets are longer and you can just run them around the exhaust manifolds. It makes it easier to change. I replaced them already once but it is difficult to get them positioned correctly. I wonder if they got too hot or pinched and maybe causing problems. I am trying to figure out an intermittent problem which is always tough.
Jeff"

I had noticed that the wires d

I had noticed that the wires do look sort of close to the ex-manifold. If replacing can the plug boot fit though this inside gap? After my recent episode of the port side manifold cracking I am imagining that due to the high heat and wire proximity I should replace them. So are these 440 wire sets for a LM440 or ? Do you have to re-time or do anything else when replacing them?

Do NOT use 440 wires! They do

Do NOT use 440 wires! They don't match up well at all. I used Big Block Chevy 454 wires.

Jeff