time to repower with diesels?

[GaryNW]

Hello all, I am seeking opinions-
I have a 1975 Hatteras 31'EC with flybridge. Current power is 1992 Marine power 454's with quadrajets. At 1700 hrs they are strong runners and produce .80 nmpg @ 23kts cruise (2800 rpm) w/full load- per flowscans. The original 150 gal frp tank has not seen E10 yet. An issue for me is that I want about 50% more range so I can run to the San Juan islands and actually fish for a few days without refueling. Currently I can get there and back but not much else. I am trying to decide on diesels or eventual Crusader 8.1's and a new tank. A typical mission would be 1/2 hour at cruise, 4 to 6 hours of trolling on one engine ( with perhaps 1/4 hour more of cruise speed to relocate) and 1/2 hour at cruise home. Such a mission is currently about $120 in gas.

Here are some knowns:
Hatteras has been able to provide the following info:
1) The diesel boats used Cat 3208n's. Same struts as the gas boats, but they couldn't tell me shaft dia or prop size or performance info.
2) My boat weighed 9.04 tons at delivery. That's boat only; no fluids. Now that is a heavy 31' gas boat !
3) My boat has 1 3/8" aquamet 22 shafts 65" long. Obviously I already knew the dia.
I have been talking to my local Yanmar dealer- according to him:
1) The 315 hp 6LPA Yanmar should work with existing shafts, existing 4" exhaust with vernalifts and existing 11/2" Groco cocks.
2) My existing morse controls are fine and we would be able to bust up Yanmar's ugly panels (all new diesels have ugly panels) and put the individual gauges into my existing holes.
3) Approx price of bobtails is $22500 ea.
I have joined boat diesel and read all 49 pages on the Yanmar 6LPA series. Most seen to like them; a few have complained of smoke and a few have had other complaints.
I have done some research on eqiuvalent Cummin's and Volvo's. The Cummins would be QSD4.2 series. I understand these are Italian motors and there have been some support issues. Volvo wants you to buy a 4 cyl with the usual balance shaft(s) to make them smooth. And the Volvo's are electronic controlled. Both Cummins and Volvo appear to be more money that the Yanmar.
Crusader 8.1 bobtails are approx $12500. So that is exactly $10000 less than the Yanmar. I am thinking a new alum tank would be about $2000 and then another $2000 to install (mostly glassing the deck back in). I could probably fit a 175 gallon tank in to help with my range issue. Does anyone have an idea of what the efficiency improvement would be with current fuel injected vortecs vs my old carb engines? This could account for the rest of the range I want.
Finally, it appears that all of my diesel and gas options would use the same gear (say hurth ZF 63's) so no $$$ difference there. In all cases, I would want trolling valves.
please let it fly!,
Gary

 

[fissioneng]

See the recent 43DC Repower thread for comments about Yanmars. There are also many other threads on this subject.

 

[Maynard Rupp]

We have a 36 Hat and I have been studying this for a year. I am an engine mechanic, so I do have some knowledge. I would look at the 330hp. Cummins 6BTA. They are sold as re-manufactured to beat some of our stupid rules. In reality they are new. I was quoted about $22,000 with a ZF 220A transmision. Do not buy a Hirth gear. Everyone says they are trouble. They are now sold by ZF, but you can easily tell the Hirth gears by their part #s. Watch out for that aluminum tank. Salt water will eat that thing alive. Fiberglass is the best material for our tanks. The 330B engines have mechanical Bosch injection systems. Folks that have them love them.

 

[BUSTER]

If you are determined to put that much work and cash into your boat,I agree with Maynard on every point.The Cummins will far outlast the Yanmars and ZF or TD trans only.If I had a dollar for every leaking aluminum fuel tank I have ever seen I could go on short vacation.Sooner or later they all leak at the hard point of sitting or attachment.I have seen tar-coated steel tanks in Bruno Stillmans and galvanized steel in Pacemakers last 30 years and never leak and I'm not suggesting them,but aluminum rarely lasts that long without leaking. Tony

 

[the kuz]

We have had good results with 330Bs in 1977 36C. Cummins approved our installation with original 5" exhausts, but required 2" seacocks, so you will need to check with the Cummins rep on those issues. 1 1/2 inch shafts (a little longer than yours I think) and 1 strut works fine. ZF 220A and 22x23 3 blade props. Lots of others here have 330Bs in 32 & 36 ft Hats, and most seem happy. There is not a lot of height to spare and depending on if/where gen is located length can be tight too -so check that.

If you plan on keeping the boat a long time, I would go diesel. You will never recover your cost when selling, but also can't find a comparable new boat for that cost. If you are willing to swap boats, there are some good deals on boats that have already been repowered, and you may get into one of those for less (net your sale) than you can re do your current boat.

Good luck, Bob K

 

[GaryNW]

Thanks all for the responses so far- please keep it coming.
I have printed out some poop sheets on the cummins line. I assume "6BTA" is of the family known as QSB5.9 ? And these are based on the engines used in Dodge trucks? One of my local marine supply houses has a reman bobtail 330 hp at 16,000. They can probably get more-I havn't discussed it with them. I am thinking this is more engine than necessary for my 31'. Recall my performance with my old 320 hp 454's. The bobtail weight of this cummins is 1350 lbs. The complete (with gear) Yanmar is 1000 lbs- exactly the same as my 454's.

I am thinking that a 36' or maybe even the 32' which sort of replaced my 31' may need/want the heavier slower turning diesel. I figure a 4.2 liter such as the yanmar or the cummins qsd would give me 25 to 26 kts cruise at around 2600 rpm's. Several boatdiesel inputers, including Tony Athens, say long life can be had if operating (cruise) at this sort of rpm. In short, I have a light and fast Hatt and perhaps a light and fast diesel is the right fit for this particular boat.

I am pretty rational about the business case sucking! Thing is, I don't care much about recovery at resale. I have never kept a boat less than 15 years (still have my 1992 22' Seasport purchased new- it has even started to appreciate in value). My new Toyota supra; I've had it for 18 years. If you bought the right thing, why worry about resale?

The reason I still consider crusader 8.1's is that IMHO the gm big block is the finest engine ever made. Bullet-proof, smooth and quiet, torque monster and parts are cheap. Only downside is love of fuel!

more later,
Gary

 

[BUSTER]

That is the way I would go Gary.For the difference in price you can buy a lot of gasoline and electronics.Gasoline is perfect in a 31' boat as long as it is meticulously maintained concerning safety. Tony

 

[Ernie Piotrowski]

Gary, you might want to consider the necessity of adverse effects of ethanol fuel on your fuel tank (doubt if a 1975 was made with ethanol resistant resin) and the cost of either having to replace at least the fuel tank or in the worst case scenario, fuel tank(s) and engines vs cost of diesels today compared to the cost tomorrow. Rarely does the cost of anything go down as the demand increases so does the cost (at least to the consumer). Demand high, supply low-raise price; demand high, supply high-raise price.

 

[GaryNW]

Ernie, I addressed the E10 issue in my initial thread (or thought I did). My tank has not seen the stuff yet, but I know it's coming and want my ducks in a row beforehand. I am assuming immediate tank replacement if I have not repowered to diesels. Tank replacement would be pretty straight forward on the 31'. The single 150 gal tank is under the aft cockpit sole; no interior tearouts.

Thing is, I love the frp tank. I tell myself it is perfectly normal to love a Hatt, but tank love is a little too much! So do I love this tank to the tune of perhaps $16000 difference between diesels and crusaders + new metal tank? Of course, the diesels would totally address my range issue.

Anyone have estimate of efficiency difference between current vortec engines and my 1992 quadrajet setup? They must be a little less thirsty. I do need to warm up my 454's for about 10 minutes to be sure they don't die as I creep out of my slip. Tight quarters so I must operate at low rpm.

Gary

Gary

 

[BUSTER]

Fiberglass makes the best fuel tank and if you have easy access to yours,simply remove it,empty it and purge it of oxygen with co2. The cover comes off easily after a little grinding and considering the tank is in good shape a good cleaning and scuffing followed by several coats of epoxy or vinylester will seal it from alcohol.Glass the top back on and you are done.I have done a couple of these and if you have decent glassing skills it is no big deal. Tony

 

[MikeP]

I'd recommend you keep the gassers and deal with the fuel tank issues however it needs to be addressed. There is no advantage that I can see in converting to diesels on that boat - just a LOT of money and more maintanance.

Those GM big blocks are good, solid, reliable engines. Parts are really cheap and they are very easy to work on. They make plenty of power.



Of course, MOPARS will smoke them on the track but that's a different issue! Sorry, couldn't resist...

 

[REBrueckner]

I like Buster's post just preceding this IF that's your real objective. Another significant factor is how many hours you run annually...the more hours/trips the more logical diesels become. But I'll bet you have the diesel bug and want them anyway. How many years would it take you to save, say, $12,000 difference between gas and diesel engine repower?? (Don't do this calculation if you want diesels.) How about a fuel bladder for extra range? (too uncool??)

Personally, I'd tend to opt for the next larger HP Yanmar, benefit from the light weight, and run at moderate RPM....below normal cruise RPM to save wear and tear. Even if such HP presses against the limits of shaft size and props, you can always limit top end via governor or mechanical control restrictions. A few hundred RPM off normal cruise means a big difference in wear. You could use the same philosophy with the CAT 3208's and retain your current props and shafts...and always add bigger shaft and props at a later date if desired.

Use the following as excuses for diesels: safety, reliability, reduced fuel costs, retention of existing fuel tank.

 

[dougl33]

$16K for one bobtail re-built 6BTA is a terrible price. Last winter I re-powered my 33 Bertram with a pair of RTO's. One was re-built. The price for the pair with brand new ZF220a's was $23K. You can still get the Cummins factory re-mans for $20K-$22K a piece with a gear.

Keep looking, you can do better.

BTW,

The 6BTA is a great engine. Its like a brand new boat. I went from cruising at 18-19 knots burning 30-32gph with my 454's. Now I'm cruising at 22-23 knots burning 20-22gph. Did I mention its like a brand new boat!

 

[GaryNW]

Some good observations. I hadn't really considered refurbing the existing tank- certainly food for thought. Actually, once a huge chunk of cockpit sole is removed, a person should be able to do the tank work with the thing still in the boat. I think this is more glass work than I want to do myself. I have been working to exhaustion on many other projects- currently wrapping up install of a Wallas 30D furnace. Nothing is as easy as you think it will be. So I need to see if I can find a local yard willing to tackle the job (with a retired engineer looking over their shoulder). Some may see a liabilty issue dealing with a certified tank.

On the business case- I did a quick calculation. Since buying the boat in July, I have been averaging $400/month in gas. If we look at 10 years and assume $500/month average- even without more useage- thats $6000/year. At the same useage and assuming gas and diesel cost the same, diesels at twice the mpg would have a $3000/year advantage. So $30000 less fuel in 10 years.

I have considered more tankage. I believe up to a 50 gal tank could be installed each side clear outboard close to the transom. No loss of useable storage and minimal loss of access to exhaust piping. I would still have access, just not as easy as current access. The weight back there would be welcome. She only sits on her lines with a full tank. A little bow down with any thing less than full, especially when carrying a full water tank.

The yanmar lp 315 hp is the bigger engine for my boat. With 550 ft/lbs torque, I would be increasing 25% over my 454's. I am pretty sure I would be looking at 40 kts top end and 25 to 26 kts at 2600 rpm. I was looking at the 260 hp version of the lp series but they have stopped making it. Maybe it competed with their smaller BMW common-rail 6.

Gary

 

[credfield]

I'll throw my 2 cents in regarding Yanmars:

I had twin 420 hp Yanmars on my last boat a Hinckley 44 Talaria Jet Boat. I was cruising at a comfortable speed (24kt, 3000rpm). I was 30 miles off the coast of New Jersey when a load noise came from the engine room.

When the engine was examine it turned out I threw a rod and there was gian hole in the this aluminum engine that provides the Yanmar's weight advantage.

The engine was built in Georgia and I was not allowed to talk to anyone about what caused the problem. No response. I wanted to visit the factory and was refused. The good news was they replaced the engine under warranty.

The bad news was that they no longer manufactured the 420 hp engine only a 440 hp. I was advised to have matched power. So I had to buy the second engine at my expense.

Bottom line: I was treated horrible for what was obviously a manufacturing or design defect. I only had about 500 hrs when this all happened.

Buy Cummins. Buy CAT.

Carl

 

[krush]

The yanmar lp 315 hp is the bigger engine for my boat. With 550 ft/lbs torque, I would be increasing 25% over my 454's. I am pretty sure I would be looking at 40 kts top end and 25 to 26 kts at 2600 rpm. I was looking at the 260 hp version of the lp series but they have stopped making it. Maybe it competed with their smaller BMW common-rail 6.

Gary

You can toss away the torque number...HP is all that matters. If you are worried about breaking driveline components, then torque matters.

 

[Jackman]

All I can say is that my boat has twin 330B's in it. Its a 32' 1985 Hat Flybridge. She is actually too fast for me with those engines. Cruises at 23kts 2200rpms and wot at 2800rpms she is pushing 32-33kts. She weighs 24,000 according to the lift scales. I think its closer to 22k with a full tank.

Anyhow, my point...There is only so much "usable" horepower and torque a Hat can handle. My boat gets squirrely at speeds of 28-30kts from keel walking. Before my repower I was considering larger than the 330b's until some people on this forum and the guy who sold me my engines talked me out of it. There comes a point at which too much horsepower becomes a waste of HP because you can't travel that fast without issues.

Second point is that if the 330b's are the limit for my boat then most likely your hull needs less HP than that to perform at its optimum level. Your boat and mine are at the dividing line between requiring and not requirin g diesel power. Understanding that, unless there is a diesel available with less HP than the 330b's the crusader 454's would be a better choice for that boat. Look at the price of diesel now. Here in PA/DE/NJ its at least 50cents a gallon more expensive in most places so the cost benefit is gone. The newer fuel injected crusaders close in on the milage benefits of having diesel so it comes down to this at this point in time (considering cost/technological benefits) does your hull functionally need a diesel to run at its optimum level?

Lastly....my arguement becomes shaky if you absolutely plan on NEVER getting rid of the boat. IF you plan on keeping it until you are in a nursing home than go for it. You'd need probably 3 gas repowers to equal a diesel repower.

 

[BUSTER]

The above is an important point.These hulls are not designed for the high speeds that many new boats run at.Hatteras hulls are designed to run well in rough conditions,but in the low to mid twenty knot range.Cut the keel,shape the keel,add rails to the chine,all are band aid solutions to an inherant and intentional design characteristic. Tony

 

[spartonboat1]

Fiberglass makes the best fuel tank and if you have easy access to yours,simply remove it,empty it and purge it of oxygen with co2. The cover comes off easily after a little grinding and considering the tank is in good shape a good cleaning and scuffing followed by several coats of epoxy or vinylester will seal it from alcohol.Glass the top back on and you are done.I have done a couple of these and if you have decent glassing skills it is no big deal. Tony

Best response and 'elegant' solution regarding the ethanol issue that I have seen. Surprised it it has not been posted before; unless I missed it.

 

[Boss Lady]

A 32' Ford was never designed to go 150 mph either, but through modernization it can. The same goes for our Hatteri. There will be limitations due to hull shape and its' interaction with hydrodynamic forces, which if you keep things realistic can provide for modern speeds for a boat in this size class, while retaining the sea kindliness that Hatts are known for, all you have to do is slow down some. Most of the refits have shown to show stable handling up to the 30 knot speed range. This is a 45+ percent increase over original speeds. If you can only achieve 28 knots before handling suffers, that is still a large increase, which most people would be satisfied with.