Yanmar 4JH3-HTE down on power - revs slowly drop off

[wheelerwbrian]

Thoughts on what caused the damage? I.e. how did the water get into the engine? So we might learn from your pain - tis the season .

[Sam McD]

Originally Posted by wheelerwbrian

Thoughts on what caused the damage? I.e. how did the water get into the engine? So we might learn from your pain - tis the season .

So we have two theories. Like I said earlier, on a return trip to NZ from Fiji, the previous owner said they got water in the fuel tank due to a poor design by Beneteau. The 523 has the fuel tank breather on the side of the hull, so if you heel her over enough in the right sea conditions, its apparently possible to get water forced up the breather and into the tank.

That was a long time ago however, and the pump was apparently inspected after that incident, so not sure on that one.

So on this boat, the fuel tank breather has been re-run to the transom to solve that issue. Learning #1.

The second possibility is that its just due to a huge lack of use combined with some dodgy fuel every so often. The boat was only used for 2 weeks every year for the last 3-4 years, so its possible (although I have no idea how this would happen without a leak) the pump somehow dried out and was run with no fuel in it at some stage??

So I guess lesson #2 is use it or loose it. Dock disease is a real thing??

Essentially the pump has run without diesel lubricating it, leading to it chewing itself up. That can only be down to 2 things. Either water, or air has been in that pump at some stage.

[nelsmay]

Gonna throw a wild one at you. I had a very similar problem on my Bayfield 36. RPMs would fall off every time to about 2000 RPMs, Same Engine. Banging my head against the wall - was it fuel, was it air or something else. Eventually discovered a small clamp on the throttle cable. Clamp was loose and as a result the cable would slide inside its jacket rather than holding the throttle lever in position on the engine. Clamp looks random and out of place but seems to serve the purpose of maintaining friction between the cable and it's jacket. When I tightened it up the problem went away.

[Searles]

Turbo boost way to low ,blade clearance increases as engine heats up Leeds to power loss,how old is the turbo ,maybe time for a rebuild ,⛵️⚓️

[Sam McD]

Hey guys, if you read back a couple of replies, you will see I found and fixed the problem. The injector pump was full of rust and metal filings and the advance and lift pump was seized. New pump, rebuilt injectors and shes making full power again.