engine issue

[blue otter]

Having a problem and need all the help i can get. I have a 2yr old sailboat with 1000 hrs on the yanmar engine, which i have maintained very well. I also have the ZF dock and go system mated to the engine. The boat traveled flawlessly from the east coast down to florida. The next time out after 5 weeks of sitting it would not rev above 2200 rpms while under way, also while this may confuse the issue it seemed to pull to the right. it has steered very straight so that felt odd.....i returned to my slip rather than the long trip i was going to take.....first i ahd a diver come and clean the bottom and inspect for a potential snag that kept the revs down and possibly contributed to the pull.....he found nothing and the prop turns freely by hand. he also watched while i engaged the doc and go which seemingly functioned as it should. I then had a ZF technician come and use his analytical tool on the ZF....no fault codes there...let me mention here that tied up at the dock with the trans not engaged the engine revs to 3200 no problem.....sounds just like it should...no noise...no smoke, no strange vibrations......also tied up if i engage the trans it will only turn 2200 rpms......again sound prefectly smooth. I have changed all the fuel filters and still the same issue......the throttle was recalibrated by th ZF tech and u can see it move from stop to stop.

Not sure where to turn now and ZF and Yanmar don't either.....the yanmar kid who showed up suggested injectors or injector pump....sound a little early at 1000 hrs for that and not in gear it runs up to 3200 just like it should.

I have seen a lot of knowledge on this site and i sure hope some of it can help now.....

Thanks in advance

[HappyMdRSailor]

Have you taken her back out?

You're not going to make full RPM in gear tied to the dock...

Other considerations:
Restricted exhaust...
Restricted or air in fuel loop...

[blue otter]

I have not yet taken it out.....but full throttle at dock shouldn't it be able to get all the way up?......the exhaust appears to be fine and i have bled the fuel lines after the filter changes

[jkishel]

A binding transmission, like something wrapped around the prop, would likely produce noticeable black smoke due to unburned fuel. You don't indicate that there is any smoke. So, I'd suspect that inadequate fuel is getting to your engine. Start by checking the fuel tank vent for blockage then the fuel pickup in the tank, then hoses to the recently changed filters. then go to the exhaust system and check the mixing elbow, muffler and exhaust hose for obstructions. if this all checks out there may be an issue with the fuel pumps.

[HappyMdRSailor]

Originally Posted by blue otter

I have not yet taken it out.....but full throttle at dock shouldn't it be able to get all the way up?......the exhaust appears to be fine and i have bled the fuel lines after the filter changes

Depends, but not likely all the way up regardless...

#1 boat 110hp turbo/40k disp, yes... can reach close to cruising rpm tied up
#2 boat 4-107 (40hp)/15k disp, not even close

Take her for a spin and see if your fuel maintenance and other adjustments have made any difference

[svHyLyte]

Check the injection nozzle/mixing elbow on your exhaust system. Odds are its badly obstructed given the hours run. BTDT...

[blue otter]

Those are good suggestions....thanks.....the diver checked the prop, no wrap and it moves freely when he spins it.....the mixing elbow looks brand. New from the outside....but worth a peek inside

[pcmm]

Originally Posted by svHyLyte

Check the injection nozzle/mixing elbow on your exhaust system. Odds are its badly obstructed given the hours run. BTDT...

I second the exhaust elbow! Yanmars are famous for burning through exhaust elbows in very short periods of time (like 700 hrs) and they're expensive to replace!!

[dlymn]

When I had reduced engine speed, it turned out to be blocked fuel filters. This can happen surprisingly quickly. If you let the boat stand with partially full fuel tanks, you will get moisture in the diesel and this will create algae growth. Sometimes this can be so much that it blocks filters and lines. Check your filters and separator, check that there's flow out of the tank. Get the fuel polished, add biocides, keep tanks full especially in storage.

[EngNate]

Hmm, just a thought here - a gear-in-reverse switch might tie into the injection system to limit max fuel when in reverse.