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History: brought the boat up to NC from GA w/o any problems...new to Yanmars and had no electronics to speak of, so I cruised on plane maybe 18-20kts. 400 hrs on the engines

Boat sat for two years through litigation issues and then modifications. Had the marina remove/replace the old fuel.

Picked the boat up yesterday, just me onboard, flat water, 100 gal fuel...20kts WOT at 3800 rpm w/ black smoke.

No real history on the engines...local Yanmar guy said start w/ a compression test and go from there. Depending on how far it is to get "there", maybe $10k (ouch)

any comments/ideas most welcome!

Ricky,
Call me sent my number to your pm.
Bruce

If you’re getting 3800 at WOT how are you only moving at 20kts? I have the same setup and would be doing over 30kts at WOT.

That’s my first question.

I talked to Ricky and feel the tachs are reading off by 2k.

He has some other issues that when he gets back to the boat next week he'll call me and I'll go thru some things with him.

Has the boat been hauled in the last two years?

Has the boat been hauled in the last two years?

Actually it's been on the hill for the last two years and just splashed this past weekend...

And a public "thank-you" to Bruce for his kind offer to help.

Happy to answer any questions and discuss...always open to learn/share. Current thinking is maybe frozen turbos.

Rick,

I had similar problems with my my 4LHA-STP Yanmar's. Lots of black smoke, no acceleration, unable to get on a plane. After a valve job, injector job and compression checks, I sprung for new turbo's and that was the ticket. It was an expensive fix, but she runs like a top now.

Good luck!

JR

Rick--I've had Yanmar 6LP's for 15 years and though I'm not a mechanic I'm familiar with them. If your undercarriage is clean the other logical cause is fouled turbochargers. When the turbochargers on these engines kick in at about 2000-2200 rpm you feel the kick, there is no mistaking it, and the boat accelerates like a rocket. If you didn't feel the kick its likely your turbos aren't working which would cause black smoke as the throttle fed more fuel to the cylinders but the turbo wasn't providing more air to combust it. Therefore the black smoke.

If this is what's happening and it sounds like it is, something is wrong with the numbers--you can't be turning 3800 rpms and only doing 20 knots unless you're dragging a crab pot which has happened to me. It is unlikely for both tachometers to be misreading by 2000 rpms.

Several of the guys on the board have dealt with stuck turbochargers, perhaps they can kick in with fix it yourself advice. And maybe just take a look underneath to be sure something isn't hung up there. That would be the best solution of all!

I've been very happy with my Yanmars so get those guys running right and enjoy them!

Doug, thanks for the feedback...clean hull and nothing underneath as the boat is on a lift...I agree with the contradiction of the speed/rpms. As part of the mods done, all of the helm electronics were replaced and the gauges are not Yanmar, so it might be the same issue for both. The turbos definitely did not spool up. I basically took the boat from the yard to the marina and put it on the lift...so maybe 30 minutes total...and packed up for home. Frustrating for the boat to be 3.5 hrs away, but I've got a long weekend coming up to check them out and probably make things worse!

Bruce wrote:I talked to Ricky and feel the tachs are reading off by 2k.

He has some other issues that when he gets back to the boat next week he'll call me and I'll go thru some things with him.

But conversely, he won’t be doing 20kts at 1800rpm either.

Sounds like an air restriction be it intake, turbo or intercooler.