Hi. I've got a Yanmar 30 on a 34 ft Hunter ('97) and for some reason the engine just doesn't have the power it used to. I used to be able to maintain about 6kts in the 2500 to 2700 rpm range, but now am lucky to be able to get 4kts out of 2800 - 3000 rpms. Oil and filter recently were changed. What kinds of things tend to cause this problem? Dirty fuel filters? Other thoughts?
Engine down a notch on power
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Early spring. But I've not short-hauled over a summer before and haven't had that kind of a drop in performance. Can algae and other growth slow things down that much?
I'll get hauled out later this year, and obviously if that's the issue then problem solved once it's out and cleaned. But if it's something that requires engine maintenance and testing I wanted to work on it while it's still in the water. Kind of a chicken and egg problem. But if bottom growth tends to be the culprit for things like this, then that's good news!
It is a place to start, dirty prop, trash on the prop, clogged fuel filters, bad injectors, bad injector pump, crap in the fuel, chose your poison. You have to start somewhere. Do you keep maintenance records? Did you buy the boat new do you know what was done when? The historical data is very valuable when this happens.
Since you are able to maintain RPMS, sounds like an efficiency issue which could be a dirty bottom.
Changing oil and filter will not change performance short term but will give you reliability and longevity.
Jim
Since you are able to maintain RPMS, sounds like an efficiency issue which could be a dirty bottom.
Changing oil and filter will not change performance short term but will give you reliability and longevity.
Jim
I don't keep a maintenance log, but know what was done and when. Bought it used three seasons ago and don't have records of prior maintenance, but boat is well kept. I haven't seen this happen before. I'll see what I can do about the engine/fuel issues while it's still in the water, and if there's no boost will then just have to hope it's a dirty bottom or prop when it gets hauled in a couple of months. Thanks!
Added to my previous post.
BTW I have a 3 ring binder on the boat and keep all my receipts for any work done on the boat in page protectors, also helps sell the boat when that day comes. Keep us posted on what you find.
Jim
No Problem with the Engine .............
It's either that, or something "REALLY" unlikely like your tach is reading high.
Interesting problem for sure
.................. let us know what the source turns out to be.
..................... as you're still able to get 2800 - 3000 RPM. I'd look for something that's adding external resistance. And likely something that's growing like crazy down there.
It's either that, or something "REALLY" unlikely like your tach is reading high.
Interesting problem for sure
.................. let us know what the source turns out to be.
Have you considered a diver? That would go a long way to making you feel more confident than having to wait. My bet is on a dirty bottom. I've read about different fouling issues in your neck of the woods this year on this and different other sailing forums.
I had a small section of bottom paint flake off and the critters tried to form an extension of downtown Manhattan on it. We did notice a 'funny eddy' when sailing and speed was down.
I go with fouled bottom. In particular a fouled prop - It doesn't take much as it causes cavitation on the prop and loses effectiveness. A quick over the side with a scrapper will solve the problem.
PS
That was my problem and solution this summer.
Wear gloves.
If you find the bottom to be clear of fouling and the prop is clean, I would check the exhaust ell. They get clogged and cause a back pressure and basically the engine can't breathe. If you continue to run with a clogged Ell, the engine will begin to overheat and cause even more damage. I would check this first before injectors or any other fuel issues.
Pirates...
I've heard a number of skippers complain this summer about the abundance of marine growth on their hulls being greater than normal and probably due to the lesser amount of sailing they've done this summer because of the lousy weekend weather systems.
Take a dip over the side and feel how "furry" your bottom has become. Down Bay where you are fouling would be more problematic.
I've heard a number of skippers complain this summer about the abundance of marine growth on their hulls being greater than normal and probably due to the lesser amount of sailing they've done this summer because of the lousy weekend weather systems.
Take a dip over the side and feel how "furry" your bottom has become. Down Bay where you are fouling would be more problematic.
I go with fouled Prop 1st.
Mixing Elbow - 2nd - in particular if it has never been changed as you mention it is 1997 boat.
I suggest a remove and replace - buy the part yourself and install it yourself or pay to have it installed. Save the old one as a back-up if serviceable.
You can add Muriatic Acid or a product called Acid Magic to break down the coked up area. Wear protected glasses, do it in an open space (fumes). Rinse with water - and chip away remaining chunks with a chisel. It might be a keeper for a backup. If you operate at low rpm for extended periods of time it will coke up and reduce its service life of the mixing elbow as well as engine cooling/performance.
After your engine is warmed up (appox 5 min) - operate it at 75-80% of max rpm for normal operation. Occasionally go to WOT (wide open throttle) for a few minutes. I do this regualrly when returning to the slip about a mile out.
Good Luck!
it isn't an engine problem, if you can still do the rpm and the boat speed is less then it is the hull/prop
but a change from 6 to 4 knots is HUGE!
but a change from 6 to 4 knots is HUGE!
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