Swapping Out Engines

[George]

I'm sorry but I have to ask. What are you doing with the boat? Fishing, cruising, long range? Does the security of knowing you have units that will run with out question ever enter your mind? What type of budget are you considering? What is your maintenance and annual usage budget? How long do you expect to keep this boat? Do you run more then 50 miles offshore? Do you plan on going to the islands? I hope that these questions don't sound rediculous, but they are important when considering this type of "SPEND" not investment. I repowered my 45' with new cats a few years ago. I cruise 28 kts at 1900 RPM, I frequently go 70+ miles offshore, I take my family away for a week every summer, litterely hundreds of miles from home with young kids. I expect to keep this boat for 1500 hours running time. I spent $160K and every single time I use the boat, it starts, and gets me home, THANKFULLY. Swapping out is not as simple as it sounds. 871s from what I recall do leak oil. Tell us your story and I think your post can be more informative Respectively, George

[Fanfare]

I don't know just what the boat weighs, except that it's heavy. I have heard that travellifts have strain gauges to measure weight, but as I am seldom around the boat when it is hauled, my requests for a weight estimate seem to get lost. And, as my wife says, each year we come down with six full suitcases, and go home with only three. Then we stock the boat for six weeks with 6-8 people, food, booze, spare parts, etc. Oh, and my books--I bet there are 200+ lbs of books alone. (I just spent the afternoon sitting on the afterdeck, in Harbour I., Bahamas, in glorious sunshine, about 75 degrees, perfect breeze, reading books and boating magazines, watching the other boats come and go--does life get any better?)

For the new engines my marine engineer estimated weight at 27 long tons, 60,480 lbs. My guess is that this is not far off when factoring in full water, fuel and about 25 gallons of lube oil.

[jim rosenthal]

JCG, first of all, I think you are on the right track with your idea about getting the engines squared away from the beginning. Since you have to remove the Detroits to do anything, I would pull them out first and see what you have. You can also detail the engine room and more easily replace/repair whatever you need to.
If you are going to repower the boat, I would go straight to modern 4cycle diesels if you can afford it. The best choice seems to be Cummins M11s, although they have a lot of competition. If you decide that the price of that is beyond what you want to spend, have your 8v71s majored and use those.
I think that unless the cost of changing to 6v92s is way below that of modern engines, you should either overhaul what you already essentially have, or go for entirely new power, which will be expensive but worth it.
One of the reasons that M11s are so popular is that they have been around and seem to have compiled a good track record- not always true with the alternatives.