4.3 starts missing after an hour or so of use

[Air Traffic]

I have twin carburated 4.3's in my boat, less than 400 hours. Went out yesterday for a ride and was running like a top on flat water. After about an hour out my port engine started missing, it would go from about 3300 rpm's drop down to about 2600 then back up again, at lower rpm's (2400) it ran steady. This happened earlier in the year and I changed the water/fuel separators, fuel filters and ran sea foam through the system and thought I solved the problem. Any suggestions on what to check next? Thanks

 

[alldodge]

Re: 4.3 starts missing after an hour or so of use

I have twin carburated 4.3's in my boat, less than 400 hours. Went out yesterday for a ride and was running like a top on flat water. After about an hour out my port engine started missing, it would go from about 3300 rpm's drop down to about 2600 then back up again, at lower rpm's (2400) it ran steady. This happened earlier in the year and I changed the water/fuel separators, fuel filters and ran sea foam through the system and thought I solved the problem. Any suggestions on what to check next? Thanks

You said it's missing, was it an actual mis or did it just start loosing power?

If it's a mis, remove the plugs and distributor cap and see what they look like.

 

[Air Traffic]

Re: 4.3 starts missing after an hour or so of use

I guess maybe losing power would be the better phrase, but why start after an hour of cruising and run steady at lower rpm's.

 

[Fun Times]

Re: 4.3 starts missing after an hour or so of use

What year is the engine (Serial number handy?) and when was the last full tune up?

Recheck the fuel filters for water, etc. etc.

Did you notice if anything was in the fuel system the last time?

 

[alldodge]

Re: 4.3 starts missing after an hour or so of use

I guess maybe losing power would be the better phrase, but why start after an hour of cruising and run steady at lower rpm's.

Might be drawing a vacuum on the fuel tank, As Fun Times mentioed stuff getting picked up and start clogging things up as you go.