871 Detroit Diesel

[seamanmt]

Howdy, have an 8 71 single detroit in a 39' seaway does anyone have experience with this engine as i have none other than its clean and loud.
boat hold over 200 gals fuel so hope it dont need it all,
thanks
Mike

[Sailmonkey]

Well, it's just an engine, the only difference between this engine and any other engine is that it's a 2-stroke. The fact that it's clean and not covered in it's own drool is amazing. The biggie with these things is to run it loaded....ie don't run around at just above idle thinking you're doing yourself a favor, without the extra load it will gunge up rapidly. the noise though is something that unique to these things.

[Chief Engineer]

The key to these engines is to get a shop and owners manual first.

There are a number of zincs on these engines......do not ignore them

Is it naturally aspirated or does it have a turbo?

Make sure that the emergency stop circuit works.

Do not use it to routinely shutdown the engine.

It is nice to put a containment can under the airbox drains.

In wintertime put block heaters in and leave them on.

Never use ether...ever...ever...it will "kill" your rings due to abnormal wear
and you can get the engine running backwards (rare).

[ggray]

Originally Posted by Chief Engineer

The key to these engines is to get a shop and owners manual first.

There are a number of zincs on these engines......do not ignore them

Is it naturally aspirated or does it have a turbo?

Make sure that the emergency stop circuit works.

Do not use it to routinely shutdown the engine.

It is nice to put a containment can under the airbox drains.

In wintertime put block heaters in and leave them on.

Never use ether...ever...ever...it will "kill" your rings due to abnormal wear
and you can get the engine running backwards (rare).

All good advice, more than I would have come up with, but can they really run backwards, incuding the blower, which I assume would be pulling air out of the cylinders?

[Chief Engineer]

From Wikipedia:

"Marine two-stroke diesel engines directly coupled to the propeller are able to start and run in either direction as required. The fuel injection and valve timing is mechanically readjusted by using a different set of cams on the camshaft. Thus the engine can be run in reverse to move the vessel backwards."

I worked on a Canadian Lighthouse tender that had a Fairbanks Morse DD. It was held by a private owner who bought it. I had to explain to him the procedures for docking the boat...I was assisted by my Best Friend who is a Master...I don't recall all the endorsements he had.

Air Start: Oh boy!!!!!!!! You had two opportunities to restart befor the Aircompressor would recharge the tanks. So there was none of that "Back and Forward, Forward and Back, Ahead Astern Throttle Jockeying
That you see "Yachtsmen doing as they scream away".

All in all it was a stout...fun boat.

[Unicorn Dreams]

You will definitely know when it runs backwards, the whole marina will also. It'll look like yout boats on fire because of the smoke out of the exhaust..

[Chief Engineer]

No injection pumps.

There are a couple special Detroit Tools you WILL need.

For Water Pump and Fuel Pump and for taking injector pipes off

They are not expensive.....better to buy them than try to make your own.

Snapon-Mac-or Any DD dealer can get them for you....you might also try NAPA

[lorenzo b]

I have one pushing my 70 ton 63 ft shrimp boat, absolutely love it. It's dry stacked and keel cooled. I read about this guy that had circumnavigated 4 times in power boats and was putting together a boat for one more trip, he chose a single 8/71.

[ggray]

Chief, thanks for the Wiki info. Lot of stuff there.

But they were talking about big ship engines which didn't have the roots blower. There was mention in Wikipedia about piston pumps on some of those big ship engines for bringing in combustion air, and that would work in reverse, but I would think a roots blower would move the combustion air in the opposite direction.

Now maybe there is/was a DD with something other than a roots blower. I'm certainly not saying there was not, because my limited knowledge is of the 53 and 71 series engines in trucks and logging equipment, and they all had a roots blower. And I just don't see how one of those could run backwards.

But I'm always ready to learn something new!

[lorenzo b]

Chief, tried to send this PM but it wouldn't go;
If I may ask your advice, I change my oil and all filters every 100 hrs of engine time and ran about 800 hrs last year which I expect to keep on doing. Is that too often?

[Chief Engineer]

150 hours or one year

on page 21 is a table

http://www.detroitdiesel.com/pdf/voc...quirements.pdf

[lorenzo b]

Very interesting
Thanks

[seamanmt]

thank you all for the info, im gathering that its a good one in a 1971 seaway built in long beach.only got 1600 hrs on meter dont know if its original.but eng looks clean and does have the cans on drip tubes.
I havent seen boat in almost 8 months due to work but wife ad i are planning a short trip and this will be first for this boat .
Agian thanks for responses when i get eye to eye with this thing im sure to have more questions,
Thanks
Mike

[seamanmt]

well im back ,seem to have lost lot of rpm only getting bout 1300 rpm engine dosent have blower,what should rpm range be and could fuel filters cause problem.

[lorenzo b]

About the only way to stop that engine is to choke off the fuel, so that is where I would look first. I once started to sputter on the ICW and pulled right over and changed out all my fuel filters, the racor was gummed up with slime. End of problem. My 8/71 tops out at 1750 rpm with a 51/48 five blade prop and I run at 1500 rpm, but they do go up to 2100 rpm, or so I'm told.