Extended Cruising vs. Outboard Power

[Whoosh]

A growing trend in mid-sized power boats, usually intended for short term family cruising, is replacing the single or twin inboard diesel with one or two outboards. I'm sure many of you have seen this given the Jeanneau Merry Fisher and NC models, the Beneteau Antares line, some of the new Sea Rays and there are many more examples. While these models are not intended for periods of extended cruising, I find them appealing for a mix of reasons and understand they will need some adapting to better fit such a mission. BUT...how to live with the recommended 100 hr servicing schedule? Given many of them are so big they will need to be lifted for engine maintenance is a puzzle: What if there's no lift?

There's a now-dormant thread here asking about the reliability of the new 4-stroke Yamahas, Mercurys and such, and the general sense from those running larger (150-300 hp) 4-stroke outboards is that their reliability is quite good, especially if used regularly which would be the case with a boat used for periods of cruising. Larger commercial & charter boats must run into this issue routinely - work the boat to earn a living vs. taking it out of service because of a 'one size fits all' schedule. It's hard to imagine they are all lifted every month or two given the expense...and yet they would be especially prone to care for their engines thoughtfully. One wonders just how diligent one needs to be to honor the 100 hr limit (especially if e.g. if the normal use case is to frequently run the engine at 2,000 rpm & hull speed for fuel conservation vs. only routinely screaming around at 5,000+ rpm). But what to do if one heads out to the Bahamas for an extended spell, where lifts are very few? Perhaps in that case, the service interval might be followed as recommended when running up/down the U.S. coastal waters but then has no choice but to extend the service interval by 50% or whatever when out in the islands.

I'm curious if anyone else has been presented this issue and has some thoughts to share. Or has experience running one or more of these engines at extended service levels and can share their experiences. And is it reasonable to believe that while a 100 hr service interval might be a safe rec for the entire population of outboards, an extended service interval is reasonable when the engine is routinely used but not worked as hard? (I know that's true of both my vehicles, where software tracks rpm, turbo use, etc. and then adjusts the recommended service intervals on the fly). Thoughts?

Jack

[carlosproa]

Good point. Depending on what to do you may have to become very intimate with the boom and blocks as it is my case

[Searles]

Be verry carefull in changing an inboard diesel of a couple of hundred hp to outboards ,the power and torque curves are totall y different ,But the big change is stability ,a diesel low down against multiple outboards further aft plus much higher up on the waterline ,this maybe a major problem on power boats up to about 30 ft or more ,get a good naval arc to check if it’s a safe alteration ,not the outboard sales person

[AKA-None]

I’d wonder if the transom was rated for outboard engines if it was built for an inboard

[Grith]

I have just changed from a large inboard ( 180hp turbo diesel with twin counter rotating prop leg) for a smaller 115hp Outboard ( in the same Imexus 28 Trailable Power Sailer but different focus design hulls).
I changed actual yacht hulls in this process as Imexus has two almost identical but structurally different hulls for each application.
My comment is that getting an outboard serviced is far simpler than getting an inboard diesel serviced even when you can take the engine to a service centre on a trailer in both cases.
After all if you have to call a technician to your yacht/ powerboat for repairs or service then it’s not that much different but if you can remove the engine and take it for repairs and or service separately it might have some lifting and transport issues but it’s still likely to be cheaper.
Finally replacing an engine is generally much easier with an outboard than an inboard.

[ranger58sb]

Jack, I interpret that to mean you might be interested in selecting a boat with outboards... not that you're thinking about converting a diesel (or gas) inboard boat to outboard power. Yes?

In any case, outboards are just engines with a drive leg attached. Modern engines seem to have a decent reputation, and the drive leg is just a drive leg... different from straight shaft but not new technology. My take is it that if a gas-powered boat will suit your mission, an outboard gas version can be as good as any... as long as the rest of the boat meets your needs.

I've seen big outboards being serviced in place, no lift/haul-out required.

You can go a long way in a 100 hours. Our last return from Ft. Myers to Annapolis was 101 engine hours, 1124 NM.

-Chris

[rslifkin]

Personally, I wouldn't want a big boat with outboards. Harder to work on than a good inboard installation, typically not terribly fuel efficient (often on par with gas inboards, but sometimes worse at low speeds). Outboards also have more corrosion concerns, no closed cooling systems, etc.

Plus, you lose a ton of transom access / space for a swim platform, etc. And I imagine if you like to fish that the outboards must be less convenient (even though people do it regularly).

That said, I wouldn't want pods or sterndrives either. I'm a big fan of simplicity, so if a boat is of a size that can reasonably have straight inboards, I'd want them.

[Chotu]

I think the servicing is the main problem. Especially given that if you are cruising you might not be near a service provider.

not to mention it’s hard to get an appointment, your boat is down for days, so in all reality? You probably don’t get that service.

that’s how I did it with mine. I have been fortunate that there have been no problems. But they have never been serviced. I have 1000 nautical miles on them.

The only service that has been done is my service. Not the updating the computer stuff and whatever that they require.

Certainly never get Outboard’s to save money. They use more fuel so you won’t save any money. I have upwards because they weigh less. Significantly less. And I have a sailing boat. It’s supposed to be sailing much more often than motoring.

[valhalla360]

Originally Posted by rslifkin

Outboards also have more corrosion concerns, no closed cooling systems, etc.

On a smaller scale (25hp) but we found the opposite. Since the entire drive train is completely clear of the water when not in use, corrosion was almost non-existent 7yrs and a couple thousand hours of use.

I've seen plenty of corrosion on inboard installations.

I wouldn't rip out a good diesel and bolt a 300hp outboards on the back of a boat but assuming a boat was designed for outboards, outboards can be a great option.

For single engine installations, a steerable outboard gives really good maneuvering control.

[valhalla360]

Originally Posted by Chotu

I think the servicing is the main problem. Especially given that if you are cruising you might not be near a service provider.

not to mention it’s hard to get an appointment, your boat is down for days, so in all reality? You probably don’t get that service.

I would think this is a plus for outboards.

Even in built up areas, it's often difficult to find a good diesel mechanic but any backwater with boats has outboards. The guy who works on 300hp bass boats can certainly work on 300hp cruising boats.

[rslifkin]

Originally Posted by valhalla360

On a smaller scale (25hp) but we found the opposite. Since the entire drive train is completely clear of the water when not in use, corrosion was almost non-existent 7yrs and a couple thousand hours of use.

I've seen plenty of corrosion on inboard installations.

I wouldn't rip out a good diesel and bolt a 300hp outboards on the back of a boat but assuming a boat was designed for outboards, outboards can be a great option.

For single engine installations, a steerable outboard gives really good maneuvering control.

It's more of a materials issue. Outboards and sterndrives are full of aluminum, so it's harder to keep them from corroding in salt water. If you can get them fully out of the water between uses, that helps, although the engines themselves still suffer internally from corrosion due to raw water cooling.



Inboards with bronze or nibral props, stainless shafts, etc. are generally more durable materials in salt water.

[Whoosh]

Interesting comments; thanks, everyone. But Ranger is correct: I'm referring to the many new powerboat models that are designed from the ground up to be powered by outboards. (I watched a video this a.m. of a Schafer 40 footer from Brazil. Handsome new boat and powered by 3 x 300 hp outboards!) These new'ish designs are equipped with outboards weighing 400-500+ lbs, so they aren't coming off their boats for service. Often these days, the boat's cockpit is designed to allow full outboard tilt-up, which beats the outdrive design since the entire engine is remote from the water after use. These designs also offer smaller boarding platforms on each side of the outboard(s) with swim ladder attached. So stern access to the boat's cockpit from a dock, dinghy or water is actually quite good.

From a cruising perspective, I guess the main puzzles I think need solving are these:
-- Fresh water wash downs & internal flushing won't be done like they can be in a marina, so how does one compensate for that? And how much is this an issue?
-- What about the tender? How do you inflate, launch, retrieve and stow it when cruising. I've seen some clever ways to address this without putting it on the cabin roof or foredeck, but a small, light and slow dink is a given; forget about RIBs.
-- Just how critical is that 100 hr service level and to what extent is it possible to extend it without hurting the engine, assuming one's use of the engine(s), day to day, can be adjusted accordingly.

Here's an example of the kind of boat I'm referring to. The walk-through is extensive but it starts with a 1-2 minute overview that will give you a feel for what seems to be increasingly typical these days for smaller but weekending/short-term cruising powerboats.

https://www.youtube.com/watch?v=YH4dBXWgkQI

More discussion on all this is certainly welcome!

Jack

[valhalla360]

Originally Posted by rslifkin

It's more of a materials issue. Outboards and sterndrives are full of aluminum, so it's harder to keep them from corroding in salt water. If you can get them fully out of the water between uses, that helps, although the engines themselves still suffer internally from corrosion due to raw water cooling.

Inboards with bronze or nibral props, stainless shafts, etc. are generally more durable materials in salt water.

But outboards typically come with flushing ports (or you can put muffs on them). Inboards have to use the more expensive parts because most are not designed for easy flushing.

Again, we simply didn't have any issues.

Another thought...I know the big outboards are expensive but so are diesels.

When we bough our 25hp, it was $5k brand new installed. They came out to the slip with a truck with a small lift on the back and lowered into position. 2hr later, we had a complete new drivetrain. A similar size inboard would be running 3-4 times the cost, the boat would need to be hauled and it would likely take a week to get the work done. We could replace the engine every 7-10yrs and after 30yrs, it would still be cheaper.

[valhalla360]

Originally Posted by Whoosh

From a cruising perspective, I guess the main puzzles I think need solving are these:
-- Fresh water wash downs & internal flushing won't be done like they can be in a marina, so how does one compensate for that? And how much is this an issue?
-- What about the tender? How do you inflate, launch, retrieve and stow it when cruising. I've seen some clever ways to address this without putting it on the cabin roof or foredeck, but a small, light and slow dink is a given; forget about RIBs.
-- Just how critical is that 100 hr service level and to what extent is it possible to extend it without hurting the engine, assuming one's use of the engine(s), day to day, can be adjusted accordingly.

If you are running 3 x 300hp engines, you will be at marinas regularly to get fuel and with the amount you will be buying, they won't mind if you use some water to flush. Regular use goes a long way to help also.

A dingy can be a little bit of an issue but can you also beach the boat because you can tilt the props up as you reach the beach.

3 x300hp ~ 30mph cruise speed? 100hr would be 3000miles. These are clearly coastal cruising boats, so you will likely be someplace where you can change it. We did it on our 25hp in the water (with some precautions to avoid spills). If you get to 110hr, it's not the end of the world but going 500hr would be 15000miles...if you didn't do an oil change that's moving into abuse and diesel manufacturers are just as likely to question warranty work if you are honest with them.

[goboatingnow]

Whatever , I’d never switch from diesel to petrol