RPM's surging, think I fixed the problem

[GMTK]

2004 Hurricane SD187 with 4.3L GXI-E, approx 190 hours on the engine. Boat had been sitting for five months and finally got to take her our yesterday. Air temp 75, water temp 57, wind 5-15mph. New oil/filter, gear oil, fuel filter all done last fall. Put in fresh gas this trip. Started up and sounded like it was running rough. Let her warm up for over 20 minutes and she wasn't happy. Got her up on plane and noticed the RPMs fluctuating 200-400 RPMs at all speeds. Ran her for about an hour and this continued. Took her back to the ramp.

Replaced the plugs, wires and dizzy cap. What a PITA job, I'm still sore. All OEM parts. Verified plug gap at .060.

Got her back to the water and she purred. I didn't have time to take her out and put her under power but I'm curious if yall think this solved my issues. Going to attach photos of the old dizzy cap and plugs (which I think were from 2004).

 

[alldodge]

The caps are known to cause trouble even when they look new. I think your plugs would have been fine after a bit of running on the new cap. In your other thread you said tank had only about 1/8 and you added fresh gas to it.

Note: checking gap is good, but don't try to regap unless no other alternative. The Iridium coating cracks easy

 

[GMTK]

Thank you sir. I no longer live close to the boat so my thinking was just to replace it all while I was there. Might even keep a spare cap in the boat knowing they have issues.

 

[Lou C]

Are those the original plugs, what's on the body of the plugs, paint overspray or rust? I agree you might want to get in the habit of changing those caps every season, start with a new one.

 

[GMTK]

Paint overspray. I think the dizzy cap is original too.

 

[Lou C]

Thought so, watched your vid on the bellows replacement again. Nice Job!
on my old 4.3 I use a set of older plugs when I fog it in the fall. Then I start it up and after the fogging oil burns off I use a set of clean plugs for the season.
I have a Prestolite points distributor in mine with mechanical (centrifugal) advance. Simple as can be. The caps usually last 2 seasons even with it sitting on the mooring (salt water) all season here in Long Island. They're about 40 bucks to replace, I put in a new set of points every 4/5 seasons or if it runs rough when I start up in spring. No throttle body fi or EFI, a 4bbl Quadrajet just like in the old muscle car days. Simple is how I like it lol....