41 & 43 Motor Yacht Owners

[Sparky1]

I own a '65 41DC which was refit with new 7.4 MerCruisers in '93 which makes it rather unique. In speaking with other owners of these boats, I've yet to find anyone with an original diesel powered version which can match my 20MPH cruising speed @ 3,000 RPM which nets .87 MPG, this with full fuel and water. She will net a bit over 1 MPG at around 8.5 MPH. I did extensive testing to prove these numbers (to myself) and was very much surprised given my experience with other gas powered boats in this size range.

What kind of speed/MPG do you fellow 41 or 43 owners get with your diesel or gas powered boats?

 

[schek]

Thanks for the posting, Randy. I'm curious myself as to relative performance.

 

[Canuck Dennis]

Sparky, I am amazed that any engine can consume 1 mpg at low rpm and then only about 15% more at 2 1/2 time more rpm, is not logical as Spock would say,
look at consumption per cu in per rpm and logic should dictate the fuel curve.

Replies will be interesting.

My 6-71 n's are close to 1 mpg at 1250-1300 rpm, 7-8 kts after that they climb drastically in consumption. Work is work...needs heat...

 

[spartonboat1]

1972 43'MY w/6-71N's. Overall in a season, about 1mpg, because I probably haven't had long runs in a 2-4 years, so much idling out, 1.5 hours at 13.5-13.7 kts on the GPS (recorded in logs), into a head sea of 0-1' at 2,180rpm, 2,440-2,450max rpm (rated 2,500) at 14.7-15.5 knts, and hull speed cruise of 8.9 knts @1,250-1,400 rpm.

So I don't have fine tuned metrics, but I know that water depth, esp. 1/2 hull length or less, will reduce speed and increase consumption, as does following seas, vs head seas, as indicated by OTG speeds.

P.s., these are 310hp J&T units and hull wgt is about 36k#'s. What is the weight of the 41DC and engine HP rating?

 

[Sparky1]

Sparky, I am amazed that any engine can consume 1 mpg at low rpm and then only about 15% more at 2 1/2 time more rpm, is not logical as Spock would say,
look at consumption per cu in per rpm and logic should dictate the fuel curve.

Replies will be interesting.

My 6-71 n's are close to 1 mpg at 1250-1300 rpm, 7-8 kts after that they climb drastically in consumption. Work is work...needs heat...

Believe me, I was very much surprised to see how these figures worked out. I may not be a technical wizard, but I do know how to fill up fuel tanks and read a GPS for speed and distance.

My first trip aboard the 41 consisted of a 50+ mile run which I made with several other boats. These guys wanted to run a displacement speeds, so I fell in line. I had filled the tanks before leaving, then I refilled them at the marina which marked the turnaround point a couple of days later having attended a "Rocking On The River" event the week-end prior to July 4th.

I didn't want to take all day to get back, so I put her up on plane all the way home running 3,000 RPM. I went straight to the fuel dock in my marina, topped off the tanks again, and did the math a second time. A few days later, we set out on an extended cruise and put a total of over 600 miles on the boat over the next several days. I checked the figures at each fill-up. No displacement cruising, just cruising at 3,000. Now before anybody points out I'm running on a river, the current on the Tennessee is rarely a factor, and it wouldn't have been on those days. The upstream run was at 1,500.

The .87 MPG figure is pretty well stuck in my head, but I don't remember exactly what the 1,500 RPM segment yielded. It was better than 1MPG, but I don't remember exactly how much better. What I do remember was that it didn't leave me feeling the need to put around for the sole reason of saving fuel. Next time I'm on the boat, I'll check my notes and see what that figure worked out to be. That aside, it looks like I'm still ahead of the diesels when it comes to a fast cruise.

 

[Sparky1]

1972 43'MY w/6-71N's. Overall in a season, about 1mpg, because I probably haven't had long runs in a 2-4 years, so much idling out, 1.5 hours at 2,150-2,180 cruise at 12.7-13.0kts, 2,440-2,450max rpm (rated 2,500) at 14.7-15.5 knts, and hull speed cruise of 8.9 knts @1,250-1,400 rpm.

So I don't have fine tuned metrics, but I know that water depth, esp. 1/2 hull length or less, will reduce speed and increase consumption, as does following seas, vs head seas, as indicated by OTG speeds.

P.s., these are 310hp J&T units and hull wgt is about 36k#'s. What is the weight of the 41DC and engine HP rating?

19,500 LBS according to the specs listed in the brochures archive on this site. I'm sure that's dry weight including the standard Chrysler engines at the time. No doubt mine will weigh more with the hard enclosure, and there may be a slight weight difference with the big block Chevy's

The HP rating at the time for the 7.4 MerCruisers was 340 in a straight inboard variation. The ratings were downgraded at a later date due to measurements being taken at the prop, but I can't remember which year that went into effect. I'm pretty sure it was after '93 when mine were new. As best I recall, that brought them to a rating of 300HP.

I don't have the prop specs in my head nor do I remember the ratio of the Hurth transmissions in this boat.

 

[Bill Allen]

My 73 43 dc with flybridge net around .6 mpg at cruise of 13 maybe 14 kts. She's really not truely on plane at that speed open her up and she planes quite nicely. Unfortunattly I won't be running like that much anymore. This is with full tanks and loaded for a cruise. I've reproped for better low end performance and find at around 7 maybe 8 mph (this is on the icw) I get close to 2 mph average. The boat seems to like going slow as do I. With 400 gallons of fuel you can pick where to get it and save a little more there. I have a 200 amp altenator on my stbd. engine and with my inverter the refrig ice maker and a few other things will continue to run without the generator eatting her fuel. I supose one of the differences with your boat may be the weight of the engines. Bill

 

[Walter P]

Bill, Your experience is basically what I have been saying for years. These old girls are cheap dates if you're not in a hurry.

Walt

 

[mobilemn1]

Sparky,,,,not trying to steal your thread here but since everyone is talking fuel consumption,,,,I have been wondering what I might get with the crusader 454's. I'm in no hurry either,,,,,7 or 8 knots sounds like a pleasurable ride to me. I know Sparky mentioned the consumption on the 41 with the mercruisers,,,,,should it be in that range.

Sounds like ya'll have some gas knowledge as well as diesal, so thought it would be a good time to ask.

Thanks

 

[SKYCHENEY]

I don't think you can really compare the 41DC to the 43DC when it comes to performance and fuel efficiency. They are totally different boats. Many of the 41's have no hardtop. Most of the 43's have a hardtop and a flybridge. Also, the 43 is much heavier, almost twice as heavy as a 41.

I think the 41 is more comparable to the 38, while the 43DC is most comparable to the older 44.

I don't know what has happened to the 43DC, but my dad owned one from 1978-83. That boat had 6-71n J&T's and it cruised much faster than most of you have posted. Maybe the fiberglass was drier and lighter back then and the engines were not as worn. I don't know, but we could cruise at 16kts and top out at 18.

 

[ThirdHatt]

Maybe the fiberglass was drier and lighter back then and the engines were not as worn. I don't know, but we could cruise at 16kts and top out at 18. QUOTE]

Sky, my friend's 1975 43DC (no flybridge) with 6-71 J&T's does 18kts when he opens her up. Talk about a flat wake, you could ski behind it! LOL

 

[Beckytek]

Daryl, I get 1NMPG at 8 k with my 454"s. I have a 1988, 40' DC. At cruising speed @3200RPM that goes to .5 NMPG. Ron

 

[mobilemn1]

Daryl, I get 1NMPG at 8 k with my 454"s. I have a 1988, 40' DC. At cruising speed @3200RPM that goes to .5 NMPG. Ron

Do you think since I am 6ft shorter and somewhat lighter that its possible I could better that,,,,I think my boat is somewher around 10 or 11k lbs.


and thanks for the post

 

[spartonboat1]

I don't know what has happened to the 43DC, but my dad owned one from 1978-83. That boat had 6-71n J&T's and it cruised much faster than most of you have posted. Maybe the fiberglass was drier and lighter back then and the engines were not as worn. I don't know, but we could cruise at 16kts and top out at 18.

Sky: Would you happen to know if your Dad's speed were knotmeter indicated or true OTG GPS knot rated. Both my knotmeters register the 16/18 knts and one day with low tanks I saw 20 indicated on the pins.

However, no doubt they need re-calibration, because I just pulled a log from Sept 08, and had recorded: 13.5-13.7 kts on the GPS, into a head sea of 0-1' at 2,180rpm and 13.0-13.1 @2,150-60rpm on yet another run. I run a little faster, since I had my stdb heat exchanger cleaned she runs cooler..

 

[Bill Root]

My 1973 43' DCMY has been repowered with CAT 3126's. I belive these engines are lighter than the Detroits most others have, as well as the Cummins 903's that were original to the boat. My top speed over ground with 24X24 props is 18.5 Knots, but the engines maxed out about 150 RPM shy of their 2600 RPM peak. I had the props re-pitched to 22 (I know, I went too far) and now the boat maxes out at 17.5 Knots at 2600 RPM.

Fuel consumption has been about on par with what others have reported. The boat is very fuel efficient in the 7.5 - 9.0 knot range, around .8 GPM. At WOT it gets more expensive at around 2.0 GPM. We're leaving Saturday to start the Great Loop, so most of our travel will be done in that fuel efficient range.

 

[Beckytek]

Daryl, Yes you should do better than me. Ron

 

[SKYCHENEY]

Sky: Would you happen to know if your Dad's speed were knotmeter indicated or true OTG GPS knot rated. Both my knotmeters register the 16/18 knts and one day with low tanks I saw 20 indicated on the pins.

However, no doubt they need re-calibration, because I just pulled a log from Sept 08, and had recorded: 13.5-13.7 kts on the GPS, into a head sea of 0-1' at 2,180rpm and 13.0-13.1 @2,150-60rpm on yet another run. I run a little faster, since I had my stdb heat exchanger cleaned she runs cooler..

Those were in the days before GPS. We once "raced" a friend with a 57' Connie. His boat could inch by us with his 8v71ti's in the spring before he took on too much water. So, those were over water speeds and both of our boats showed about the same on the knotmeter.

 

[Sparky1]

I don't think you can really compare the 41DC to the 43DC when it comes to performance and fuel efficiency. They are totally different boats. Many of the 41's have no hardtop. Most of the 43's have a hardtop and a flybridge. Also, the 43 is much heavier, almost twice as heavy as a 41.

No way the 43DC is going to weigh almost twice as much as the 41DC, and they are not totally different boats. The layouts are almost identical, the beam is the same, and I can't for the life of me see where that extra 2 feet went on those I've boarded. No doubt the freeboard is higher on the 43, but that's about it. There's no doubt the 671's weigh more than 7.4's, but I can't see any of that resulting in double the weight.

As for the hardtop and flybridge, my 41 has a hardtop which I'm sure weighs more than the factory version on the 43. As for the optional flybridge on the 43, we're talking maybe 3-400 lbs. max as per additional weight. I have to question the weight on the 41 the brochure lists as it makes no distinction between gas and diesel powered versions and seems pretty light. It is also my understanding the 41DC's would have been laid up heavier than the 43's. This was disputed in an earlier thread, but there's no doubt the early Hatts were overbuilt based on everything I've read. Maybe I'll give Hatteras a call later and see if they can confirm this.

Bottom line is, on the 41DC, my gassers beat the diesels for speed and efficiency at speed. As far as I know, the 43 wasn't available with gas engines, so it is indeed a bit of an apple and orange comparison when you throw it into the mix. 41DC's were not available with 7.4 MerCruisers either. I'll be happy to prove my numbers to anyone who submits a signed offer to purchase (or buys the fuel).

 

[Bill Allen]

My numbers where based on 400 gallons fuel (what 2400lbs.) full water tank (800 lbs) inverter battery bank (8 golf cart batterys) very full refrig, few cases of beer and of course full liquor locker. Last two did get lighter as we traveled, I'm told it's shrinkage from being in a damp area. We also had all the stuff one carried when traveling. So how much did the boat weigh, have no idea. When I bought her had her on a fancy travel lift, low on fuel, no water, no inverter bank or personal belongings and the scale on the lift said 36,000lbs. Bill

 

[Sparky1]

Maybe I didn't make my point clearly in comparing weights between a 41 and a 43. We all know about HP to weight ratios, and that's part of the equation when comparing gas and diesel engines. There is no doubt the extra weight is a penalty.

I would say the bare hull weights are within 1,000 lbs in a 41 vs 43 comparison. Too bad we don't seem to have more 41DC diesel owners on here to see how they stack up. I'd like to hear from other 41DC gassers too who are running the original Chryslers or whatever.