53MY speed info please...

[mikep996]

In my internet and broker-searches for our next boat - a 53MY, I've found a great deal of what appears to be conflicting information re cruise speed/max speed.

Everybody seems to list something different. I realize that naturals and turbo-motors will have different max speeds but I've seen 53MYs with naturals listed with a variety of different cruise/max speeds as well as turbos with equally different - though usually higher - speeds.

I realize that some may be listing the "advertised" speeds for these boats, whatever those were. Others may be listing what they usually cruise at and whatever top speed they have seen from the boat.

So, I would appreciate some factual info on this from the 53MY experts here - both naturals and Turbos. What do you normally cruise at and what is the max speed you have observed from the boat? Can a natural cruise at 13Knots or is that turbo-motor country?

I tried to find some info on this using the search but was unable to locate anything specific.

Thanks,

MikeP

[mwert72655aolcom]

I own a 1974 with the 871TI's rated at 435hp. Fully loaded with a clean bottom, she'll cruise at 16.0kts at 2060 rpms and top out at 18 @ 2300, and add 0.5 knots in shallow water. The problem you'll get into here is different conditions, props, and amt of extra load placed on the engines so technically I could still tell you she'll "cruise" at 16 under any conditions, but of course the question is whether that speed represents 10% off the WOT value, which is where you should be in terms of an honest cruise. I will tell you up front, though, that these boats are so comfortable and so heavy and fuel is so costly that I don't "cruise" that often - a good autopilot is really the most important "option" on these boats, not the bigger engines. If you're looking for speed, I'd look elsewhere. Good luck.

[Nonchalant1]

I own a 1978 53MY with 8V71TI's (435HP). Following are the specs for my boat, fully loaded with a clean bottom, measured at two 180 degree directions and averaged:

Idle (no wake) speed = 5.75 knots
1,200 RPM (low wake) speed = 8.9 knots
1,700 RPM (displacement cruise) = 11.0 knots
2,000 RPM (planing cruise) = 18.0 knots
2,300 RPM (WOT) = 19.1 knots

Fuel burn runs from .85 gallons per nautical mile at 1,200 RPM to 2.0 gallons per nautical mile at 2,000 RPM.

[PascalG]

mine is a 1970 with naturals and I cruise around 1500rpm and 9.2 kts. that's in 10 to 12' water. in 6' it drops by as much as 1.5kts.

total fuel burn is around 9 gph...

top speed was about 14kts last time I checked... (months ago) but i wasn't getting rated RPM.

I doubt that a 53 with naturals could cruise 13kts and if it did, MPG would be really bad since at that speed the boat woud be pushing a big wake and not be on plane...

so far it's been almost a year and I don't regret having chosen the naturals... sure more speed woudl be nice sometimes but i dont want the extra maintenance. Of course, i'm almost always in biscayne bay or the keys where waters are usually pretty flat so hull speed is jsut fine...

[BEC53]

My 53ed cruises at 15 to 16.5 knots in fresh water, depending on the fuel load and condition of the bottom. I have 6v92's at 465hp and the fuel consumption is about the same as the 71's, even though Detroit called these the "fuel-squeezers". I still would rather run at about 1300, which gives me 9.8 knots and 11gph. I agree that a good autopilot is important at these speeds, also stabilizers work great at 10 knots.

[mikep996]

Thanks...


Speedwise, the Admiral and I have determined that we will be quite happy in the 10-12 knot range. I'm expecting the 53 MY to do that with no trouble and at a "reasonable" fuel burn. Hope I'm not "over-expecting." :)

I'm just trying to sort out the reality from the specs shown in many of the adds.

[Nonchalant1]

Your best MPG will be at hull speed, which is 9.1 knots. At 1,700 you'll do 10-12 knots but you're pushing a lot of water uphill and MPG really drops. Also, with these DD engines, you have to run them hard enough to get them up to good operating temps to "blow them out" for at least 15 to 30 minutes per day, or you'll carbon up the rings. For the 8v71TI's, that means lots more tha 10-12 knots. I slow cruise at 1,300 RPMs and 9.1 knots and displacement cruise at 1,700 too. Then at least once per day, I go up to planing speed for a while. 2,000 RPM's gets them up over 180, but stay below 185. On a long crossing, I can plane the whole day.

I like the TI's because on a long trip it's nice to run 17-18 knots sometimes, even at 1.9 gallons per mile, and the DD's are made to run at those speeds all day. If you take care of TI's, you'll get 5,000 hours out of them before overhaul, but Pascal's right about naturals having longer life than that as a tradeoff for slower speeds.