Planning to repower

[labytheshore]

I'm planning on repowering.
Boat to be docked in Manasquan for at least the next 8 years.
What has the service experince been for Cummins, Volvo, and Yanmar?

[TwinFin]

I can only comment

on Volvo Penta service in my area so this won't be a lot of help to you but.... I'd say it's been scratchy at best. I've contacted three authorized service providers in my area over the past 4 years and only one mechanic has really impressed me. It seems like most of them just have not seen a lot of these engines and they are not on top of the relatively common problems reported here and on boatdiesel.com. I'm not much of a diesel mechanic and I feel like I have been helping too much with diagnosis.

Fortunately my only engine problems to date have been a very small gasket leak on the port side (had that fixed), and recently I blew two fuses on my port supercharger (had the clutch repaired at my request based on what I learned here and on boatdiesel).

KAMD300's

You are asking the right question. Mac advised me to base my engine selection in large part on the quality of my local service providers. It's hard to tell what they are like before you need them but spending time talking to guys with experience near your marina is time well spent. I'd also recommend a phone call to Tony Athens just to ask him what he thinks about your top two engine choices. He was very helpful when I did this.

[Capt B]

As far as I know - the only volvo and yanmar dealer near manasquan is Monmouth Marine - and I wouldn't have them touch as much as a wiper motor. I know that there is a yanmar dealer in Forked River off Riverside Dr. and a Cummins tech in Bricktown that comes highly recommended - but the reason I went with Cummins - a mechanical engine - (4BTA) is that you can do all of the maintenance and installation yourself.

[labytheshore]

Capt. B
I thought that would be the general feeling towards Monmouth Marine.
However I think the Cummins 6b is going to be extremely Large in my engine room. The 4 B is not available any more.
Does any one in the area (Pt. Pleasant within an hour's radius) have the Cummins 6B package?

[backman]

Check w/the factory

talk to one of the Privott's 1st. I don't think you can get the Cummins 6B or the Volvo D6 into an old engine room.

When i repowered my choices boiled down to D4, KAMD 300 or Yanmar 6LP for size and space reasons.

The new engine room is a few inches longer and has a wider hatch which allows better access than our pre 2K old style engine rooms.

[Tswann]

6B

What year is your hull?? I had 6Bs and a genset in my 2001 28. The genset made it tight but it was still workable. 6Bs can be had through the reman program.

Feel free to email/call me if you want info on available remans from Cummins

[labytheshore]

The 6B was suggested by Keith Privott. Although the Cummins 6B may be tight.
Keith had also suggested looking at another boat with that power package.

There is a post some where on the Board with water intrusion on the D-4, which has me concerned.

[backman]

No D4 water intrusion

I had an issue this winter when the covers were taken off that some water had pooled on low spots on the engine and had caused external surface rust on the injector housings.

There was not any intrusion and my opinion was that this was caused by improper maintenance somehow when my boat was put away last winter as opposed to a systemic problem.

[Patriot]

Although there are always opinions as to the best diesel engine for these boats if you to take an engineering view versus one of brand loyalty and public opinion you will find these answers:
1. The CC-28 is limited by a marginally small prop diameter. That is why the Cummins 6B series cannot achieve it's full pontential in these boats. A great engine but at it's cruising and WOT rpms there is some sacrifice to it's true potential as seen in boats that can turn a bigger diamater wheel. May be the best engine for a long life but not for economy or performance in the CC-28.
2. The CC-28 needs a lot of torque at cruising speeds , it is a big and heavy hull hull to push at 25-30 kts where the boat performs best. The engine "match" at cruising speeds is critical. Since this hull performs best and is designed for a bare minimum 24knot cruise the engine performance curves are worth a serious look for a hull that doesn't get happy until 24kts and is limited by prop diameter to such a point that it becomes very important. The very reason that you hear about Acme props and high prop cups are because this boat has a very small useful range of power. Matching the power is key.
3. The Yanmar 6LP has a very flat and peak torque curve that is a near perfect match for the CC-28. Combined with a HP curve that reaches max at 3000 rpm and holds until WOT, the "match" is hard to dispute for this hull. http://www.yanmarmarine.com/products...P_TechData.pdf
4. The Volvo 260 may be a good engine but where you want peak torque it is already falling off at a steep rate. By pushing the rpms to a good cruising speed for these boats you are well down the torque curve this engine is capable of. Running this engine past 3000 rpms is on the wrong side of engine design. Peak HP also comes right at the end of throttle range/WOT which is never one of my favorite curves. http://www.volvo.com/NR/rdonlyres/8A...60_inboard.pdf
5. You could move to the Volvo D-4 @300 hp but that engine produces another torque curve that peaks at 2500 rpms and falls off rapidly at 3000 rpms. Neither of those torque features is ideally matched to the CC-28.
6. The Volvo D-6 @ 330 Hp at first seems apealing, 6cyl, electronic tehnology etc but look at the torque curve where although achieving a similar, well engineered flat range on the upper torque curve similar to the Yanmar the peak comes in too low and falls off at a very rapid rate after 2600 rpms. This is also a very tight engine in the CC-28.

Make your decision based on the right power match for the boat combined with local sevice support. Always remember that a 4cyl diesel in a 18000 pound loaded boat is working very hard. The 6 cyl choices each present some advantages and disadvantages but pay particular attention to the torque and HP curves and relate them to THIS hull. They are all good engines but they are not all great matches for this hull.

[backman]

Yanmar props and RPM for 25 knots?

Nice analysis - I agree w/ your conclusions about torque and effective HP at cruise.

I thought the Yanmar's could not swing the 18 X26/19 X 26 props the slower turning Volvo's and even slower turning Cummins did since its a 4000 RPM engine as opposed to 3500 (Volvo) and ~3000(Cummins).

I also thought they had to be run at 3200 or so to hit the magic 24-5 knots?

A very useful table for a buyer/repower to construct would be of the various engine options to indicate speed/RPM/prop size.

I would agree w/ Patriot's assessment that choosing an engine that can be run at 75-80% RPM to produce 25 knots fully loaded is the way to go.

The Yanmar wins hands down on the size and weight factor, no question about that.

On repair - the Yanmar's had valve issues in the past which I presume are long past solved. As a mature mechanical engine its foibles and behavior is well understood. There are plenty of 2000+ hr Yanmar's out there.

The Volvo D-series is new and I am one of the pioneers w/ 1100+ hr's on mine. Few non commercial D-series have more than 2K hours and its misbehaviors as they age have yet to be known.

Volvo parts, especially w/ 7 computers in the boat are pricey and as I am seeing; when a sensor partially fails; it takes a lot of back and forth w/ mechanic and Volvo to figure out what is wrong.

Code Blue in Hawaii had terrible problems w/ the computers which as I recall took 1/2 year or more to sort out.

[Patriot]

The Yanmar valve issue was a real problem. There were two service bulletins that went to dealers but they never reached "recall" level to alert owners. Yanmar has now lost the class action suit brought against them and owners of affected engines enjoy an extended 7 year warranty for valve related failures. If anyone owns a 1996-2002 Yanmar SLP and needs the details of the service bulletins drop me a note. The details of the class action settlement are here: http://www.yanmarsettlement.com/

The issues Larry points out with computers/electronic controls is a consideration for sure. I am quite happy having straight mechanical engines but soon there will be no such choice due to the ever tightening emmision requirements now being put on marine diesels. There will be growing pains with computer and electronic control reliability during the transition period for sure but that will all get sorted out soon enough.

With regard to prop sizes and the Yanmar one needs to be careful, although the engine is rated for 3800 WOT most smart Yanmar techs will tell you to prop for a 4000 rpm WOT heavy load and then never exceed 3800. That in itself takes a little edge away from the Yanmar across the cruising rpm band where you are essentially propping with a smaller pitch to satisfy an engine load requirement that costs you fuel at cruise and top speed. There is also a big performance difference between an older Yanmar CC-28 propped boat with the Michigan wheels and those enjoying the Acme's these days. The high propeller slip rates on the Michigan props are horrible for these hulls. I should have haulled and swapped props but my new Acme props in the box will have to wait until next season. In talking to Mac about swapping the Acme's out waterborne he suggested not to do that because the "bite" of the Acme is so much greater than the Michigans that you want to ensure a real fit on the taper. They have run into swaps where the key was inhibiting a good taper contact. Since you never want the key to have a torque load on it and several have sheared because of that it is a very important process to get right. The procedure is to pull up the Acme prop with no keyinstalled, mark the forward progression point on the shaft with a pencil with the prop nut fully tightened then pull it back off and see if the Acme goes up to the same mark with the key installed (which it most likely won't). That forces you into hand fitting the key such that it does not interfere with the prop taper making full contact. As a diver who does a lot of underwater work I almost went after the swap anyway but decided against it. I'll do it after haul-out and get it right.

[Hey Doc]

Considering Price and Size Constraints

Aftering owning both a 28 with 315 yanmars and the 28 with D-6's, I'd confirm previous posts that both are good engines.

Considering the price differential and the potential electronic problems Backman cites, on a repower of a 28 I would suggest the 315 yanmar is probably a better choice.

Also, the D-6's do take up a bit more space than the yanmars and I'm sure they would be real snug in the older engine room layout.

Patriot has some good info on the torque curves in his post. However, you might want to test run a newer boat with the D-6's. I can tell you from running both boats, the D-6 feels like a much beefier engine than the 315 yanmar. The boat is much quicker out of the hole and it does not bog down with a heavy load in rough seas. For example, if you set the throttles to 2800 rpm's the boat will run exactly on 2800 regardless of how rough the seas may be. With the yanmars, you will get some variance in your engine rpm's as you climb up and down waves. Also, the yanmar has some turbo lag until it reachs 1800 rpm's and the turbo's spool up.

With this in mind, I think the cost of the repower and your service availability should be top considerations in your decision.

[Patriot]

The D-6 should surely feel much beefier, it is. The engine displaces 25% more than the Yanmar 6LP. (336CI to 254CI). With regard to engine rpm drop while climbing a wave, that is a function of a mechanical engine and every mechanical engine ever made displays that trait. Your Volvo is designed to hold a constant rpm going up hill or down, that is one of the benefits of an electronic engine. When you set your throttles in the Yanmar you were setting a very specific fuel rate regardless of load when you set them with the Volvo you are asking a computer for exactly xxxx rpms no matter what the load, very different types of fuel control.

After looking at the specs of the new D-6 variants (330, 370 and 435 hp) I would really consider the 370hp variant. Some research with gears and props would be required and the end result may be that our CC-28 prop diameter limitation just doesn't support that much power.

When I see the new CC-32 offered with power options up to 960HP I get jealous.

[Hey Doc]

370hp will not work for sure

Mac, will not put the D-6 370 in the 28, citing many of the concerns that you have cited with prop limitation and being more power than the boat is designed to have installed. However, the 330 is a great package for the 28'. Mac is currently building one for our fellow member bluefin 32. I believe the prop diameter limitation you are considering is assuming that the boat has a 2:1 gear ratio. Even then, you can still utilize all that power. Hawk is running a 19x26 on a 2:1 ratio and he has a true 30 kt cruise fully loaded.

Don't get me wrong, I like the yanmar 315...it is a great engine. It is just hard not to be impressed with how well the D-6 performs in the 28.

[Bluefin 32]

Yes that is right about Mac's view of installing a rating greater than the D6-330 in a a 28. I explored it briefly before settling on the D6-330. The issue is that the prop diameter is limited to 19" and in order to attempt to utilize the higher horsepower, the pitch would have to go well over 26. That makes the prop "oversquare" by too much and would increase slip to the point of not being adequately efficient.

The alternative of using a lower gear ratio such as 1.5:1 instead of 2:1 is also not workable although it would solve the pitch issue. There the problem is that the prop shaft rpms would become very high at cruise giving rise to cavitation, noise and vibration concerns and reducing efficiency. In fact, with heavy boats Volvo recommends higher gear ratios and would have preferred that the factory use the 2.5:1 box with the D4 if that would have worked.

There is no getting around the fact that with the prop diameter limitation of the hull pockets, there is only so much power that can be delivered efficiently by the available blade area.

An option that might work if anyone wanted to experiment is a D6-370 with jackshaft to a DPH sterndrive. The dual props can deliver the power and the combination of a more efficient thrust angle and the greater power would give you a preposterous cruise speed -- I bet 37-38kts. Anyone who plans to keep their 28 on a small freshwater lake that they need to cross in 5 minutes instead of 7 minutes should consider such a setup. The rest of us would find it totally useless on the open ocean. I have a friend with a 68 Viking with twin 2400hp engines that can cruise at 37 kts and he has to slow down too when seas build to 4-6 feet, though not as much!