So why the Detroit hate?

[rsmith]

MikeP crunched the #’s some years ago that showed the efficiency of these newer engines were not that much better than the old DD’s. In reality it takes so much energy to move X amount of weight or mass. Lighter engines may do a little but a couple thousand pounds in a 60,000 lb boat isn’t really significant. Most of us carry 6-8000 lbs of fuel and water. Some hullor running gear mods may get more bang for the buck. In my case going to one piece shafts made a huge difference and added almost 2 knots. Full length lifting rails on a 53C will make a huge difference.
IMO repowers in the smaller boats make more sense. We repowered our 34 with 3160 Cats made a huge difference over the gas engines. The extra weight and speed dried the boat up and made it into a real canyon hopper. But even then in 1971 my dad paid 13,500 for the repower which was more than half of what he paid for the 34 new in 1965. I’m sure Dr Jim’s 36 is a huge improvement over the 3160’s. 41’s are a great repower also. I’ve blasted around Chesapeake bay on Krush’s 41 with the 8.3 Cummins at 30 kts. Probably the best thing like Krush did was to find one someone’s already done and suffered through the teething problems.

[Westfield 11]

Perhaps "hate" was the wrong word. But I have heard plenty of "avoid at all cost, time bomb, worthless, not worth rebuilding, etc.) on THT where every now and then someone is interested in moving up in size to and older SF or MY. Conversations always go south by second page and original poster gets no help and thinks it's not safe to move up unless repowered. Then budget is busted.

I thought THT was mostly an outboard and center console fishing place. Are they really the right people to ask about diesel boats?

[rsmith]

I thought THT was mostly an outboard and center console fishing place. Are they really the right people to ask about diesel boats?

Bunch of yahoo’s over there pretty much.

[Passages]

I don't understand the "hate" either. Yes they are noisy and leak some oil but they will always get you home as long as you have fuel, air, and oil.

The 6-71's on Passages are nearing 3000 hours and still running strong with just normal maintenance. Same with Aphrodite's 8v92's at 2800 hours.

[Boatsb]

MikeP crunched the #’s some years ago that showed the efficiency of these newer engines were not that much better than the old DD’s. In reality it takes so much energy to move X amount of weight or mass. Lighter engines may do a little but a couple thousand pounds in a 60,000 lb boat isn’t really significant. Most of us carry 6-8000 lbs of fuel and water. Some hullor running gear mods may get more bang for the buck. In my case going to one piece shafts made a huge difference and added almost 2 knots. Full length lifting rails on a 53C will make a huge difference.
IMO repowers in the smaller boats make more sense. We repowered our 34 with 3160 Cats made a huge difference over the gas engines. The extra weight and speed dried the boat up and made it into a real canyon hopper. But even then in 1971 my dad paid 13,500 for the repower which was more than half of what he paid for the 34 new in 1965. I’m sure Dr Jim’s 36 is a huge improvement over the 3160’s. 41’s are a great repower also. I’ve blasted around Chesapeake bay on Krush’s 41 with the 8.3 Cummins at 30 kts. Probably the best thing like Krush did was to find one someone’s already done and suffered through the teething problems.

MikeP put less than 30 miles a year under his keel so I think his numbers may be a bit off.

From experience on multiple vessels with and without repowers I can tell a few things.

1) Detroits as a whole are almost indestructible. They run forever if asked too But Some bigger HP versions are less reliable. They are big, heavy and in a vessel that's not looking for speed can provide years of service.

2) Newer electronic engine technology is 10% more efficient after the tree huggers get to it. Even then the lower weight, higher HP and cleaner burning of fuel makes for a better experience especially where wifes are concerned.

3) I've seen repowered motoryachts done on a budget and little if any benefit was seen from the cost.

4) I've seen repowered sportfishing boats done on a budget with the same outcome.

5) I've seen and been involved with repowers that upgraded the vessels and customers were amazed at the added performance. You get out what you put into it.

Ask any 34c owner with detroits if they plane well. Then compare to the cummins 5.9 repowers and see what they say.

Take a 53c with 1271n engines and replace with qsm11s at 700+ Hp and see how it changes the boat.

It's all in what you want from the repower. Pulling out 425 hp detroits for 450 hp cummins C series is kind of a waste unless you dont plan to run on plane. C series goes to 600 hp and outlast the mechanical engines because of better fuel and ignition management. Even better I've seen qsm11s at 330 HP in passage makers and on one boat it had 30k miles in 5 years under its keel with nothing but maintenance.

[madhatter1]

I thought THT was mostly an outboard and center console fishing place. Are they really the right people to ask about diesel boats?

It generally is but many others on there as well. Dockside chat provides some entertainment as does "the bilge". The regional sections are very good for info on water depths, anchorages, and marinas when planning trips.

There are also a bunch of A-holes on there that are part of the package. I may possibly be one!

[jim rosenthal]

ACtually, MikeP and Loretta put quite a bit more miles than that on their boat, especially when they first had it. Later on, when they wee commuting between three continents, they used it much less, which is why it was sold.

MikeP is meticulously careful and absolutely honest. I would trust his analysis of anything to be as good as he could possibly do. I have seldom met anyone with his level of experience and knowledge.

[rsmith]

ACtually, MikeP and Loretta put quite a bit more miles than that on their boat, especially when they first had it. Later on, when they wee commuting between three continents, they used it much less, which is why it was sold.

MikeP is meticulously careful and absolutely honest. I would trust his analysis of anything to be as good as he could possibly do. I have seldom met anyone with his level of experience and knowledge.

MikeP did a whole analysis not just from his experience but charts and graphs of data from other sources. I had a few disagreements with him real world vs theory stuff. But his analysis and research was usually spot on when it came to tech stuff.
And Scott a 34c with factory Detroit’s could barely do 14kts since 4/53’s was the only DD that would fit.
Speaking of 34 repowers my dad knew John Rybovitch we visited the yard when I was a kid in the mid 60’s. Rybo was outfitting brand new 34’s. They were ripping out the 440 Chrysler’s and putting in 534 Seamasters. That was a Ford truck engine I believe modified by Holman Moody. They were crazy fast for the day and could kick a 37 Merritt’s butt.