Laurence Cranfield of Auckland, NZL asks:
I am in the process of buying a N46 and survey just done. Survey says that Lugger L6414D will not run at full rpm of 2450 rpm without overheating. I realise you would not normally want to run at full rpm and this vessel normally runs at 1750 rpm for about 7.1 knots.
I am told that "all N46s overheat when run at full rpm" and wonder if you
can confirm that. If you want any information concerning NZ or cruising in NZ I will be pleased to help.
Also when this purchase is complete I will advise you and maybe we could
stay in touch.
Jim Leishman of Nordhavn responds:
Your Lugger 6414 should run at full rpm without overheating.
What is probably happening is that your engine is coming up over the temp at
which the alarm switch is triggered (it's set at 205 degrees) and you're
getting an overheat alarm. John Deere sets their alarm temp much higher - at
about 230 degrees. Most of the time the engines will run up to 210 or 215
degrees and then stabilize.
In any case what happens over time is that the keel cooler gets a film
coating within its interior which is caused by "silicone dropout" from the
anti freeze solution that has been run in it. The only way to get rid of the
insulating coating is to remove the keel cooler and have it boiled out at a
radiator shop. We see the need for this about once every six or seven years.
A few of more things to check:
Make sure that the bypass screw on the keel cooler is closed so no coolant
is allowed to bypass.
Make sure that the exterior of the cooler has received no bottom paint or
coating of any kind.
Check the two thermostats in the top front left hand side of the engine
under the flat four bolt plate - to make sure they are operating properly.
We have seen them stick.
Make sure that the antifreeze mixture is correct and hot to rich on glycol.
Pure water has better heat absorption then glycol so keeping the mixture
lean will improve cooling.
Scott Flanders of Egret responds:
In addition to Jim's reply we found Egret rises in temp then stabilizes as
mentioned. We have never run Egret more than 5-8 minutes at wide open
throttle at a time. We do this periodically to blow out the carbon from the
engine and stack from low rpm running. After hauling in Turkey this spring
we dropped the keel cooler and found a very hard brown crust on top of the
cooler tubes. After much effort with power driven wire brushes it was
clean. We regularly clean the cooler tubes while diving in warmer waters
and spray the tubes with muriatic acid when hauled. The brown crust was a
surprise. We immediately dropped five degrees of engine temp after
cleaning. The prop needs to be clean as well before sea trials.
Egret only turns 2350 rpm's at WOT but she is a heavy boat with the flybridge and all 'stuff' aboard.
We hope the 46 for sale comes up to standards or is brought to standards.
They are wonderful boats, well designed and engineered. It will serve you
well for the trek north to the S. Pacific islands and back to NZ. Egret
plans to be in the Bay of Islands in December 07 then moving near the
Auckland area when our family arrives for a visit over the holidays. We
would be happy to meet you at that time. Good luck.