6-71 T question

We´re interested in a boat with 6-71 T1 (435 hp at 2600) engines that have 2000 hours. In doing a general search, I´m not reading too many favorable things on them. In fact some people tell others to "run from them." I'm looking for more knowledgable info before I spend a lot of money on a mechanical survey.

Thanks

Well, at one time, the inline 6 71 would have been the ONLY power you would have likely been looking at in a boat. But, that was a long time past.
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It is now some VERY old technology with the last engine block cast at DD over a 1/4 century ago. The turbo was an "add on" that, though it wore it well, the engine never really was designed for. You will NEVER get any green, fuel savings awards with those engines.

Having said that, I will have to say that I love the old 6 71N and would be SUPREMELY confident of it getting back to port in any situation.

To expand on the above, the 6 71T has been called by many...including me...bullet proof. If properly reconditioned, operated and maintained, you could expect many thousands of hours of service from them. Even when they aren't treated with the utmost respect they still are known for firing right up and gettin the job done.

They are not all that fuel efficient though and these days it can be difficult to find someone competent that has experience working on them. There are still plenty of parts available because there ar still many, many, many yachts and workboats alike relying on them for propulsion and electricity. But if you're not the type of skipper that wants to get a manual and spend some "quality time" in the engine room, you should first try to find a good tech to help you keep them tip top.

Good luck with your decision.

Thank you for the info. We are coming from a boat with Chrysler 440s so I am hoping fuel sonsumption is better. We travel at 9 kts whether gas boat or diesel so I hope consumption is better. Chryslers burned 9 gal total at 9 kts.

Can the 671 T be used at trawler speeds 75-90% of the time?

Well, fuel consumption is so subjective with hull design, weight and distribution, props, etc.. But all things being equal, the diesel should give you much better fuel numbers.

The 6 71 is an engine that is very comfortable working at any speed EXCEPT idling. No 2 cycle diesel... as well as most ANY internal combustion engine... does well at idle.

The 6 71 should not be idled for any extended time for any reason. Excessive idling will cause early bearing wear due to insufficient lube pressure as well as upper cylinder carbon loading due to incomplete combustion. There is also the phenomenon particular to the 2 stroke liner design called "oil slobber". Wherein the air charge in the scavenge box remains low and allows oil to "back up" into the box excessively. To the point the air box drain tubes can't keep up clearing it out. This can result in the cylinders "gulping" oil with the incoming air charge and this causes added carboning of the piston crowns and can cause rings to break. The oil also tends to adhere to the piston ports due to heat and, over time, will slowly reduce them in size. Bad Ju-Ju!

They are the happiest at around 1,800 to 2,300 rpm as that is typically the "sweet spot" in the torque curve. They were made to run wide open, as it were, and that is where they would give the biggest bang for the buck fuel consumption wise. That is why they were so beloved in getting cargo from point A to point B. But, like I said, they are very capable and reliable engines that should do well "trawilng" at 9 kts.

Good luck with your new (to you) boat.