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Old 08-18-2018, 01:06 PM   #1
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Inboard diesel vs outboard gas

Interested in comments about diesel vs gas engines for maintenance and hassel - a 200 hp diesel, for example, vs a 200 hp Honda outboard.
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Old 08-18-2018, 01:30 PM   #2
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GAS outboard vs DIESEL inboard

I don't allow Gasoline inside my boat cabin or any internal enclosure any where on my boat. All gas must be stored externally outside of the cabin of my boat.

WHY ? -- The Fumes are explosive.

That said Gas engine are cheaper than diesel & much more light weight.

I personally think Diesel engines are more durable, more efficient, safer to operate & are better suited for what my boat is - that being a full displacement long range Diesel trawler.

However, if you have a plaining boat, then a gas engine might be what your looking for. However, the Boat needs to be set up for that with several key things to be safe with that fuel.

As far a out boards as power plants on boats, they have been used for decades & have been used for almost every usage - However - in bad weather, out on the open ocean, I'll take an inboard Diesel any time over an out board of any type.

Good luck with the thread as I am sure many have their own opinions on this subject.

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Old 08-18-2018, 02:25 PM   #3
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Well I just sold a boat with a 370 hp Yanmar inboard diesel and am buying a boat with a 70 hp Yamaha outboard. Two very different boats and each has the right engine for them.

So back to your question: I sold the diesel powered boat because I was tired of crawling around in the engine room fixing things. Things like changing raw water impellers are a PITA on that engine. Normal routine oil changes were fairly easy particularly with the built in oil change pump with no Houdini contortions required. But you do have to pump oil up not drain it down outside as in a 4 cycle outboard. The oil filter is a little hard to reach and does require climbing down in the engine room to change it. The other big maintenance chore is the after cooler cleaning which does take a full day but fortunately only every 5 years or so.

So yes, the inboard diesel does take more hours and more bodily contortions to do the routine maintenance. I am looking forward to the outboard where everything is out in the open and fluids drain down and do not have to be pumped up.

There are lots and lots of other good reasons to pick the diesel over the outboard, but all depend on the boat, the engine, the hours used each year, etc. But you didn't ask about those questions.

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Old 08-20-2018, 05:42 AM   #4
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If long range is the main consideration diesel wins , as the fuel is denser.


Otherwise gas is great for a little used ,( few hundred hours a year) boat as maint is cheaper .
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Old 08-20-2018, 06:08 AM   #5
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Fundamentally diesel is a different and more effienct combustion process. Add to that that most diesels are turbo. This makes diesel the only option for a bigger boat.
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Old 08-20-2018, 06:28 AM   #6
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To the OP, size of the boat and number of engines makes a significant difference. On my 45' boat, working on the single inboard engine is far easier than an outboard. Twin engines on a <35' boat, give me the outboards.

What kind of cruising will you do? If you travel off the beaten path with a single outboard, changing a raw water pump impeller would be a big PIA compared to an inboard.

Other considerations will include the loss of a hot water loop for the water heater, and a likely a lower amp 12 volt supply for charging house batteries.

I think the outboard's big plus comes when doing repairs with the boat out of the water. In water repairs becoming much more challenging, especially on anything more than flat calm water.

I wonder, over a ten year period, whether the routine maintenance costs more or less for the 200 HP outboard or the inboard?

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Old 08-20-2018, 08:43 AM   #7
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I think the outboard's big plus comes when doing repairs with the boat out of the water. In water repairs becoming much more challenging, especially on anything more than flat calm water.

I wonder, over a ten year period, whether the routine maintenance costs more or less for the 200 HP outboard or the inboard?

Ted

I certainly agree with the first paragraph. I assume that the OP's outboard powered boat is trailerable, so all maintenance is on land. On the water outboard repairs are virtually impossible.

If you are paying a mechanic to do the maintenance, I am quite sure that the diesel is more expensive. The mechanic has to come to your boat and is then faced with access issues. For an outboard, you trailer your boat to the outboard shop and for many reasons, outboard repair rates are cheaper than inboard diesel rates.

Changing an outboard's impeller is more work as you have to drop the lower end. But comparing the effort to change the impeller on my 370 hp Yanmar in a Mainship Pilot 34 (and the cussing due to dropped nuts and busted knuckles- the pump really has to come off to change the impeller), I think I would rather drop the lower end of an outboard in a nice clean driveway with all of the stuff sitting in front of me.

One thing I didn't address in my posting above is maintaining other boat systems: macerator pump, fresh water pump, A/C raw water pump, etc. Much depends on access, but on the Mainship, they were all installed around the big engine in the available corners, so Houdini contortions were required. This of course may not be the case in a trawler with a single engine in a large engine room. But in general such systems are installed in more accessible locations in an outboard powered boat.

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Old 08-20-2018, 09:15 AM   #8
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While the rates may be cheaper, I'm wondering if there is more maintenance to be done over 10 years on a gas outboard versus a diesel inboard.

My area on the Chesapeake may be an anomaly, but dealer labor rates for outboards versus inboard diesels are about the same. With the computer driven fuel injection systems of prime mover outboards, gone are the days of the low tech outboard mechanic. Guess they figure if you can afford a 350 HP V8 outboard, you can afford $100+ per hour labor rates.

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Old 08-20-2018, 09:46 AM   #9
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Hi Never too late,

Unless you're comparing very similar boats with either gas outboards, or diesel inboards (I can think of only a few, such as the new versions of Cutwaters, for instance), your question is difficult to comment upon. Obviously, comparing "maintenance and hassle" of a (typically) larger, diesel inboard cruiser such as the majority of this forums' participants operate to a (again, typically) smaller trailer boat with an outboard engine is like comparing an apple to an orange.

There appear to be several new-construction builders (Aspen Power Catamaran, Ranger, MJM Yachts, etc.) that have begun to offer outboard power as an option to diesel in larger boats. Sheesh, the MJM 53 is huge! But none of them seem to address the issue of how the heck does one service outboards on larger cruisers without haulout? Even a simple oil change is a major PIA while hanging over the transom on an outboard-powered boat while in the water. And ALL engines require routine service, including oil, water pump impellers, spark plugs (for gas engines, of course), valve adjustments, etc. And while trailers remain an option for some of these larger boats (Cutwaters certainly, MJM 53's not so much), having to haul on the trailer to perform simple maintenance seems to me to be a major PIA.

Personally, every time I go in my engine room to do routine maintenance and/or inspection of my John Deere diesel, which I do virtually every time I'm aboard, I am pleased I don't have to trundle down to the travel lift and haul to do so. So I guess I'm not so much a proponent of outboards for larger boats. But YMMV, and for those that reach for their cell phones instead of a toolbox in case of engine issues, outboards may be the cat's meow.

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Old 08-20-2018, 09:48 AM   #10
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The Great Harbor TT35 uses outboards @ 60-70 hp each. Easy to get to and service. Cost new what $7k? Good for 3500hrs, at least. For that cost you could keep a spare around.
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Old 08-20-2018, 09:52 AM   #11
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Originally Posted by djmarchand View Post
I certainly agree with the first paragraph. I assume that the OP's outboard powered boat is trailerable, so all maintenance is on land. On the water outboard repairs are virtually impossible.

If you are paying a mechanic to do the maintenance, I am quite sure that the diesel is more expensive. The mechanic has to come to your boat and is then faced with access issues. For an outboard, you trailer your boat to the outboard shop and for many reasons, outboard repair rates are cheaper than inboard diesel rates.

Changing an outboard's impeller is more work as you have to drop the lower end. But comparing the effort to change the impeller on my 370 hp Yanmar in a Mainship Pilot 34 (and the cussing due to dropped nuts and busted knuckles- the pump really has to come off to change the impeller), I think I would rather drop the lower end of an outboard in a nice clean driveway with all of the stuff sitting in front of me.

One thing I didn't address in my posting above is maintaining other boat systems: macerator pump, fresh water pump, A/C raw water pump, etc. Much depends on access, but on the Mainship, they were all installed around the big engine in the available corners, so Houdini contortions were required. This of course may not be the case in a trawler with a single engine in a large engine room. But in general such systems are installed in more accessible locations in an outboard powered boat.

David
I really liked my Yamaha 4 strokes and you have mentioned the raw water impeller as one item that takes longer than my diesels already. These are a few other items on my Yamaha's that were not just a token service:
- Timing belt (gear needs to come off)
- vapor separator service
- valve clearances
- exhaust plates (if applicable)
There are also likely a few internal zincs that are not too hard to service but many folks do not look for them.
All in all really liked the Yamaha 4 strokes but not quite as little work as some would have you think.
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Old 08-20-2018, 10:43 AM   #12
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But none of them seem to address the issue of how the heck does one service outboards on larger cruisers without haulout? Even a simple oil change is a major PIA while hanging over the transom on an outboard-powered boat while in the water. And ALL engines require routine service, including oil, water pump impellers, spark plugs (for gas engines, of course), valve adjustments, etc. And while trailers remain an option for some of these larger boats (Cutwaters certainly, MJM 53's not so much), having to haul on the trailer to perform simple maintenance seems to me to be a major PIA.

You nailed it. A boat like the Great Harbour TT35 is billed as the ultimate Great Loop boat but if you have to haul every 1000 miles (roughly 8 knots times 100 hours between oil changes, you will have to haul the boat 6-8 times on the loop. Definitely a PITA. Sure a trailer helps but how do you get the trailer to 1000 mile (100 hour) sites for routine maintenance. Can't wait to read a loop blog on how this will be handled.
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Old 08-20-2018, 11:07 AM   #13
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You nailed it. A boat like the Great Harbour TT35 is billed as the ultimate Great Loop boat but if you have to haul every 1000 miles (roughly 8 knots times 100 hours between oil changes, you will have to haul the boat 6-8 times on the loop. Definitely a PITA. Sure a trailer helps but how do you get the trailer to 1000 mile (100 hour) sites for routine maintenance. Can't wait to read a loop blog on how this will be handled.
FWIW - I have done all of these maintenance items while backed into a slip with the engine next to the dock - except for the valve adjustment. The impellers are typically not needed for many years in these outboards but I have dropped a drive to do one in the same slip situation. It was more than 100 miles away from our home and it was easier to do it remote than trailer it back home - that was with twin 150Hp Yamaha's.
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Old 08-20-2018, 11:35 AM   #14
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Outboards in salt water certainly have their challenges. This notion of predicted engine hour based maintenance must be coupled with age based maintenance. Have many on this thread looked at outboard aluminum corrosion on water pump housings, block water passages and prop hub splines? Yeah, inboards will cause more ER time in the hole but at least the fasteners are not locked into soft metal. Area salinity varies but I will not keep Al in the water ever again.
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Old 08-20-2018, 12:51 PM   #15
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You nailed it. A boat like the Great Harbour TT35 is billed as the ultimate Great Loop boat but if you have to haul every 1000 miles (roughly 8 knots times 100 hours between oil changes, you will have to haul the boat 6-8 times on the loop. Definitely a PITA. Sure a trailer helps but how do you get the trailer to 1000 mile (100 hour) sites for routine maintenance. Can't wait to read a loop blog on how this will be handled.
In the blogs I read about O/B powered boats on the loop, a typical way to service the boat is to haul it out on a travel lift and service the engines while the boat is still on the lift. Even with changing the impellers it shouldn't take more than an hour or two (once you've done it a couple of times).

You can also change the oil with an oil extractor (like used on a "real" engine). This can be done with the boat in the water.

Also, since you are using the motor in a constant low power mode (if you cruise at trawler speed), you can lengthen the service interval on the oil changes without issue.

With the TT35 you could also cruise at hull speed on one engine a lot of the time. This would extend the service interval quite a bit.
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Old 08-20-2018, 01:02 PM   #16
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I’d much prefer gas outboards.
I love outboards.
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Old 08-20-2018, 01:17 PM   #17
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Outboards free up interior boat space for other uses. Outboard I would think less stinky compared with a diesel engine.

I have read Europe is going to ban diesel engines, at least in and around cities since they pollute worse than gasoline.

If there is less demand for diesel, that may make diesel prices higher. Hard to imagine that happening here in the USA. Maybe in 50 yrs time.
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Old 08-20-2018, 01:17 PM   #18
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http://www.salinityremotesensing.ifr...-ocean-surface

As with most chemical reactions, rate is subject to the density of reactants (NaCl) and temperature. Thus a big diff from SE US and NW US.
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Old 08-20-2018, 01:27 PM   #19
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Thanks to all for your comments. I started out convinced that I wanted a 30-35 foot trawler with a diesel, but it seems people who own boats in that category spend a lot of time on maintenance, and I'm an older guy; I don't have a lot of time. Or mechanical knowledge. So I started thinking that maybe I should be considering something on the order of a Rosborough or C-Dory. Now I don't know what to think.
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Old 08-20-2018, 01:36 PM   #20
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I love the smell of diesel in the morning ...

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