1985 61 Hatteras MY with De-Tuned 12-71 TIs 2000 Hours

[happyours]

I am planning to look at a 1985 Hatteras MY which appears to be in excellent condition. The listing asserts that the engines are 12-71-TIs 650 HP De-Tuned to Commercial Work Boat Standards (New Rated HP is 450 HP). Engine have approximately 2,000 hours.

I have been asking but have so far not found anyone who recognizes this designation and/or able to say if this is a net positive on this boat. Since we would use the boat primarily in trawler mode it seems like a positive but it would be nice to confirm that. If we decide to proceed we will certainly have a proper engine survey and hopefully that will clear up the subject. However it would be nice to have the best understanding possible before proceeding with an offer and survey.

Any suggestions or comments would be appreciated.

[oscarvan]

Never heard the term, but I don't know everything. If I was a betting man I'd say some of the old Hatts are gonna come along and raise the BS flag. All I can think of is smaller injectors.

[happyours]

Never heard the term, but I don't know everything. If I was a betting man I'd say some of the old Hatts are gonna come along and raise the BS flag. All I can think of is smaller injectors.

Thanks

[Cricket]

Pretty common to "detune" engines, especially 2 stroke DD"s which were probably "tuned" too high in the first place for some of the applications. Think it's a good thing for what you're trying to do. Guess my one question is would it be better/helpful to have a higher gear ratio in this case?

[happyours]

Pretty common to "detune" engines, especially 2 stroke DD"s which were probably "tuned" too high in the first place for some of the applications. Think it's a good thing for what you're trying to do. Guess my one question is would it be better/helpful to have a higher gear ratio in this case?

Thanks for the insight. Good to hear from someone who is familiar with de-tuning. Most folks react with a quizzical stare when I bring it up. Might take the survey to know abut the gear ratio. Brokers don't seem to have a wealth of specific information like that immediately available. Someone did bring up the subject of the props needing to be tweaked.

[jim rosenthal]

Some marine engines were offered in different power ratings, along with instructions regarding how hard and long you could run them. I think a C or D rating means commercial or workboat use, where they could run at WOT all day, all the time. Pleasure craft use restricted you to something like "no more than 1/2 WOT out of five or six hours" or something like that. I'm sure when they built the engines to a lesser rating, fitting smaller injectors was part of the plan.

450hp is a rather modest rating for 12-71s, but as long as they'll turn up to rated RPMs and they pass an engine survey by a guy who knows DDs of that vintage, I would not be worried about them.

Actually, 12-71TIs at 650 hp are not at the highest power rating, either. Seems like they were offered in higher numbers than that, but not certain.

You might be able to find more information on boatdiesel.com, too.