Hesitation under acceleration and start up issues

[Mike717]

2004 270 SunDeck 496 Mercruiser HO

Hey all,

I just got this boat a few months ago and just started experiencing a knocking at idle and during acceleration there is some hesitation, it struggles to get on plane but once on place and running at 2700 RPM or more, there's no issues. Almost like the fuel is being turned on and off. Any suggestions.

Additionally I'm having issues starting the engine, but this was from day 1, no associated with the above issue. I replaced the batteries and the issue persists. When turning the key I hear what sounds like one revolution of the engine, then silence for 3-4 seconds, then another revolution, one more, then it cranks. It turns on every time, but I have a sneaky suspicion that this is leading to a place I don't want to end up at.

Thanks

 

[Espos4]

2004 270 SunDeck 496 Mercruiser HO

Hey all,

I just got this boat a few months ago and just started experiencing a knocking at idle and during acceleration there is some hesitation, it struggles to get on plane but once on place and running at 2700 RPM or more, there's no issues. Almost like the fuel is being turned on and off. Any suggestions.

Additionally I'm having issues starting the engine, but this was from day 1, no associated with the above issue. I replaced the batteries and the issue persists. When turning the key I hear what sounds like one revolution of the engine, then silence for 3-4 seconds, then another revolution, one more, then it cranks. It turns on every time, but I have a sneaky suspicion that this is leading to a place I don't want to end up at.

Thanks

Any maintenance history?

Plugs, wires, exhaust?

The starting issue could be low voltage from poor or corroded connections, or the starter may be on its way out. There is a fuse down by the starter too.

Hydrolock is always a worry too.
I think you have full closed cooling so the manifolds should be good, but the spacer blocks and elbows can corrode.

I would start by removing the starboard manifold and get a good look At the starter. If it’s old and rusty, you could start there.

A compression test would be helpful too.

 

[Mike717]

Thanks Espos,

I think I finally found a professional mechanic who is going to come look at the issues. Your information is helpful, I don't want them making up reasons and going down the wrong rabbit hole and taking months to figure something out.

I will follow up once we've fixed the issues.