Cummins or 3406

[Mako 36]

How about a little help?

45' Sportsman 1984 692 Detroits 550 Hp. Should I rebuild or repower?

If I repower should I go with 3406 Cat's or Cummin's in the 500 or 600 Hp range?

[seapower]

It's a matter of what you can afford. If you are able to afford "either" way, then re-power is what I'd be looking at. Cummin's get's the hod from me, as could be predicted. Frank

[Artson D]

Have been around Diesels a long time and I would have to say Cummins hands down! Parts are cheeper and easier to get and they are much much easier to work on from a owner stand point. What model and year were you looking at? I subscribe to the cummins web site for business reasons and cant say enough about it! If you are a owner of a cummins you can also subscribe for free and register you engine(s) serial# and get parts, operation, and maintenance manuals. Let me know if you need any info on a possible future purchase of engine, i could look up info for you if you like.

[Mako 36]

Have been around Diesels a long time and I would have to say Cummins hands down! Parts are cheeper and easier to get and they are much much easier to work on from a owner stand point. What model and year were you looking at? I subscribe to the cummins web site for business reasons and cant say enough about it! If you are a owner of a cummins you can also subscribe for free and register you engine(s) serial# and get parts, operation, and maintenance manuals. Let me know if you need any info on a possible future purchase of engine, i could look up info for you if you like.

Thank,

I've got 2 6v92 550HP in a 45' Sportsman, needs rebuilding so I'm debating
( if I can Afford) to go with 480 or 500 HP Cummin's.
I've been told that would save me about 2000 LBS. and still get decent cruise and fuel economy

[seapower]

Let me revise what I said earlier. It really depends on 2 things in my book. #1 how many hours a year are you looking to realistically to use it a year? #2 Can you really afford the re-power and all the extra's that go with it (un-forseen cost's, cause nothing will fit)? If you are going to have a nice family type fishing boat, instead of one that is going to be expected to run daily, then I would say you're way better off rebuilding. We all know that the fuel price is more than likely going to rise, but you can run alot of hour's on the difference a re-power will cost. Now if it's going to be used daily and alot of hours a year, then yes the re-power to me makes sense. I just got off a 37 ft Bertram that has the same power your boat has now. Those old Detroit's will run along time if re-built "properly", just don't cut any corners (and don't hire a hack to do the job). One thing that really help's that engine is the rpm you run them at. Historically the guy's that I see with them that don't get many hour's out of them, run them waaaaay tooooooo hard. For instance, I ran this boat for the owner (he and his family were on board) for a 3 day fishing trip this past summer. The first thing he wanted to do was turn them at 2250, I said what are you doing????? Well I alway's run them there, I told him "not for long". I trimmed the boat out and slacked them back to 1950, well he only lost about a knot and a half, plus his fuel burn went way down. He now run's them at 1950 and that's it. The 92 serie's won't take overheating either, so if they start creeping up, find out why. Just my 2 cent's. PM me if you like and I'll give you my cell #. Frank, SeaPower

[Artson D]

I would have to assume that these are early electronic or mechanical? I do agree with seapower on the run time, but one of the worse things you can do with any engine is let it sit and not use it. Affording a mechanic that knows what he is doing and the proper parts is still going to cost a pretty penny! Being able to rebuild a two stroke Detroit is almost a lost art! Make sure that you have a well seasoned mechanic that has done more than a hand full of these before you hire them!!! But Lets step way back and keep this simple, shall we. What gives you the feeling that they need to be rebuilt or you need a repower? If I could make a suggestion to you, why dont you find a company...marina, or certified mechanic that could do a oil sampling for you on the engine oils. I deal alot with fire apparatus, over the road trucks, and heavy equipment and sampling is virtually a blood sample from your engine. It would tell you things like bearing wear, silicon levels(dirt) and moisture content along with many other known metals from various parts of your engines. That would give you a good indication of what shape your internials are in. Hope this helps out a little.

[Mako 36]

I would have to assume that these are early electronic or mechanical? I do agree with seapower on the run time, but one of the worse things you can do with any engine is let it sit and not use it. Affording a mechanic that knows what he is doing and the proper parts is still going to cost a pretty penny! Being able to rebuild a two stroke Detroit is almost a lost art! Make sure that you have a well seasoned mechanic that has done more than a hand full of these before you hire them!!! But Lets step way back and keep this simple, shall we. What gives you the feeling that they need to be rebuilt or you need a repower? If I could make a suggestion to you, why dont you find a company...marina, or certified mechanic that could do a oil sampling for you on the engine oils. I deal alot with fire apparatus, over the road trucks, and heavy equipment and sampling is virtually a blood sample from your engine. It would tell you things like bearing wear, silicon levels(dirt) and moisture content along with many other known metals from various parts of your engines. That would give you a good indication of what shape your internials are in. Hope this helps out a little.

Thanks for the help guys,

Yes these are early DDEC's 1984 with ZF gears, the starboard motor was tore half way down in 2005, inboard starboard side pistons, sleeves, rods, and head are junk.
The motor was left open to the elements for 5 years.
Why it was torn down is a mystery, previous owner has passed away, the mechanic is
in jail. and I want to get her up and running.
I've got a vry experienced mechanic coming to look at her, but I want to know how much should be reasonably spent on a rebuilt 692 before you go in another direction?

[seapower]

You will have no way of knowing how much it will cost until you have broken down all the way. Thats when you will be able to see if the crankshaft and cam shaft are worn. Other than that you will be replacing the liner's, pistons (& rings), bearings,oil pump, injetors, heads serviced, seals etc'... From what you are desribing it will be an expensive re-build, just because you don't know why it was disassmbled in the first place. Don't stop digging until you find out why, other wise you'll possibly throw a pile of money out the window. Leave no stone unturned. Listen to what I am telling you here. Frank

[tom s]

in my mind it comes down to affordability AND how much you like the boat.I have repowered many boats over the years and there is aways extras.IF you like the boat and you put a pair of 4 cycle engines it it you will wonder why it took you so long to do it.As for the make,have had both Cats and Cummins and both good.Have 3412s in my 44 Luhrs now.Tom

[Artson D]

Thanks for the help guys,

Yes these are early DDEC's 1984 with ZF gears, the starboard motor was tore half way down in 2005, inboard starboard side pistons, sleeves, rods, and head are junk.
The motor was left open to the elements for 5 years.
Why it was torn down is a mystery, previous owner has passed away, the mechanic is
in jail. and I want to get her up and running.
I've got a vry experienced mechanic coming to look at her, but I want to know how much should be reasonably spent on a rebuilt 692 before you go in another direction?

Personally I would not even consider putting the time and effort into a engine that has been left open for that long. Remember one thing...if your car breaks down you pull over. If your boat breaks down 120 miles off the coast...........
Is their alot of corrosion in the engine? Was it near salt water while it was open? Cant go wrong with a matching set of 6BT cummins!!!