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Can't reach WOT. Wrong props?

W

waterant

New member
Can you help with the issue I'm having?

Both engines can't reach WOT under load and lots of white smoke after 2500rpm

Boat: 2002 Mainship 430
Engines: 2x Yanmars 6LY

Starboard: 400 hours, all exchanges taken off and cleaned, new injectors and turbo 2 years ago

Port engine: completely rebuilt 2 years ago with 150 hours after rebuilt.

Here is the data from my recent testing:

- With no load, both engines go to 3600rpm, no smoke

- Max rpm under load is 2870 on both , checked with a mechanical tach
Oil pressure 70 psi, turbo boost pressure 22 psi, temperature is normal at 170F

- max speed is 16 knots (2 years ago I could get 20-21 knots with no smoke under similar conditions)

- Hull and props were cleaned by a diver 2 weeks ago

I don't think the problem is with the engines because one was completely rebuilt with all new parts inside and out but both engines behave the same.

Any ideas what can cause low WOT under load and excessive white smoke?

Do I need to reduce the pitch of the props?
 
Last edited:
White smoke may indicate unburned fuel.---Or contaminated fuel.----Any water in the fuel?----Checked water separating filters ?-----I would start with compression test on both engines.----Post the numbers here.
 
Thank you for your reply.

I recently replaced 3/4 of each tank with fresh fuel (a month ago) and added 64 oz of Diesel Kleen to each tank (2x 200gal)
previous full refill was last fall.
Water separators do not show any water in them. just clean red fuel

I'll recheck the compression, but it was good on both engines 2 years ago when I was doing the main overhaul. It would be strange if compression changed much on both engines at the same time.

Anything else I can check?
 
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