Inboard Or Outboard?

[Factor]

Originally Posted by monte

Hehe I can imagine my fridge if I didn't defrost and clean it each month or two. It would end up looking like a big brown iceblock. I guess if I didn't have food in it and kept it on a low setting it might last a year between cleans..

You need to buy a quality Australian Made ICEER system. Not the cheapest but worth every cent, and uses very minimal power. Great refrigeration systems.

[CruiserAD]

Hi all

Interesting thread! Can anybody comment on high thrust outboards except the well known Yamaha 9.9? Are there any equally reliable high thrust OBs around 25-40 HP available?

Im considering outboards on a 45 foot aluminium cat but the small Yamahas would be far to small for that.

Regards Jan

[44'cruisingcat]

Yamaha do a 25 HT and a 60 HT.

[JohninTally]

This is a very relevant thread for me since my position and the OP's are remarkably similar including his shortlist. The only difference being you are a few years ahead.
So, I'm curious, what did you wind up buying Saildriver? And why? It would be very instructive for me to know. Assuming that you have purchased a yacht, what do you think of you decision? Would you change anything? Assuming of course you notice that your old thread is bumped!

[valhalla360]

Wow there is a lot of mis-information here.

[QUOTE=Goosebumps;1798066]It seems to me that a reality check is usefull here. Like always it is firemost important to determine what you will use your cat for, wgere, how?

Serious long range cruisers won't choose outboards to propel their cruising yacht. To carry more petrol than you need for your dinghy outboard is simply very irresponsible. I have a secure dedicated petrol (for dinghy outboard) locker that drains between the hulls st the stern of my cat. Wgere would I store more petrol. Outboards propelling the cat would consume much more than your dinghy outboard. Where on a small, under 36 foot cat would you store that extea petrol. I have 350mile range stored in the original tanks that are all bottom vented between the hulls.

If that is not a serious enough argument against outboards to propel a multihull think of the battery charging. It is one of the most important issues for a long term long range, of the beaten track, far from popular, tourist infested , cruiser. And the days of running the motor to charge the batteries are fading fast. Solar is more reliable, quieter and long term cheaper to cover house loads. Your idea that you need upwards of 850watts of solar panel is crazy high unless you use a ton of electricty.

Cruisers spend lots of time on the hook out of marinas the marine diesel engine has to run regularly to keep it in good condition, the non-load running can harm the engine but with the lias of a few Hp because of high rated alternators resolves this. If that's your concern, pull up the anchor and take a 15 minute cruise around the harbor to get the engine up to temperature and you will likely save fuel and properly load the engine while also exercising the steering, transmission and the rest of the drivetrain.

The dragging of the inboard propellers is a non-issue amongst the cruisers. Foldi g propellers are a gimmick. To keep them free from marine growth is extremely difficult. They will stop folding ir unfolding with just a bit of marne growth, and we cannot anti-foul them. Who is putting folding propellers on thier outboards? You get the best of both worlds. Reliable fixed propellers and no drag under sail with outboards.

Inboards can be located in very difficult to reach bilges under cabin berths. I would not go for multihull where you sleep on top of engine, where diesel smell cannot be eliminated, where engine noise, vibration affects you. On my 34foot Catalac inboards are in spacious stern lockers reached from the cockpit. An outboard that can be lifted into the cockpit, is even easier then going head over heels to reach the motor.

Cruisers know that working on outboards is challenging because of the fine mechanical design. If you service, change all filters, oil, use anti-freeze in your engine coolant, make sure your through bhull seacocks are in good condition and valve closes Inboard diesels basically will keep going if you give them clean water free diesel, simple baya filter will help there and discipline handling the fuel. Who puts anti-freeze in an outboard and where is the seacock? What exactly is difficult about keeping an outboard going? I have to belive you are still under the impression outboard design is the same as it was 30yrs ago.

Hobbyhorsing of any multihull in heavy seas will affect your outboards. Some are designed to run even when submerged but we all kniw it will only be matter of time before damage occurs. The position of the outboard propeller has tobe in the ideal drive position to be efficient, fuel and power wise. Only efficient o flat seas. Once up and down movement starts in the waves imagine the poor efficiency. Inboard propellers, typically on saildrives mounted far from stern in front of the rudders, will remain efficient even in heavy seas. The flow of water from the propellers will make the rudders, steering, much more efficient to. And if it's that bad, are your diesel air intakes going under water? I've never came close to putting the outboard underwater. With the outboard that steers, it's even better than relying on propwash over the rudders. It even steers in reverse. Of course, if you are talking twin engines, it's irrelevant as standard procedure is to leave the helm centered and just work the gears/throttles.

Autopilot on rudders used in combination with outboards simply dont wirk as smooth as they do with inboards. How so?

Sure outboards will be best for the weekend cruiser because marine diesels have to run. This sentance doesn't even make sense. Could you clarify what you are trying to say. All engines are better off with regular use. [/QUOTE]

As it turns out we are actually considering a Catalac 10M. I'm struggling with the fact it needs new saildrive seals and motor mounts. For the cost to have those replaced (And still have a 20yr old drivetrain) I could get a brand new outboard. And that's regular maintenance recommended every 7yrs. Our current boat has an 8yr old outboard that still works flawlessly with nothing but normal maintenance. Pending the results of the survey, will probably proceed anyway but definetly a drawback. Unfortuantely, the design is not conducive to retrofitting outboards.

[Goosebumps]

[QUOTE=valhalla360;1815137]Wow there is a lot of mis-information here.

Originally Posted by Goosebumps

It seems to me that a reality check is usefull here. Like always it is firemost important to determine what you will use your cat for, wgere, how?

Serious long range cruisers won't choose outboards to propel their cruising yacht. To carry more petrol than you need for your dinghy outboard is simply very irresponsible. I have a secure dedicated petrol (for dinghy outboard) locker that drains between the hulls st the stern of my cat. Wgere would I store more petrol. Outboards propelling the cat would consume much more than your dinghy outboard. Where on a small, under 36 foot cat would you store that extea petrol. I have 350mile range stored in the original tanks that are all bottom vented between the hulls.

If that is not a serious enough argument against outboards to propel a multihull think of the battery charging. It is one of the most important issues for a long term long range, of the beaten track, far from popular, tourist infested , cruiser. And the days of running the motor to charge the batteries are fading fast. Solar is more reliable, quieter and long term cheaper to cover house loads. Your idea that you need upwards of 850watts of solar panel is crazy high unless you use a ton of electricty.

Cruisers spend lots of time on the hook out of marinas the marine diesel engine has to run regularly to keep it in good condition, the non-load running can harm the engine but with the lias of a few Hp because of high rated alternators resolves this. If that's your concern, pull up the anchor and take a 15 minute cruise around the harbor to get the engine up to temperature and you will likely save fuel and properly load the engine while also exercising the steering, transmission and the rest of the drivetrain.

The dragging of the inboard propellers is a non-issue amongst the cruisers. Foldi g propellers are a gimmick. To keep them free from marine growth is extremely difficult. They will stop folding ir unfolding with just a bit of marne growth, and we cannot anti-foul them. Who is putting folding propellers on thier outboards? You get the best of both worlds. Reliable fixed propellers and no drag under sail with outboards.

Inboards can be located in very difficult to reach bilges under cabin berths. I would not go for multihull where you sleep on top of engine, where diesel smell cannot be eliminated, where engine noise, vibration affects you. On my 34foot Catalac inboards are in spacious stern lockers reached from the cockpit. An outboard that can be lifted into the cockpit, is even easier then going head over heels to reach the motor.

Cruisers know that working on outboards is challenging because of the fine mechanical design. If you service, change all filters, oil, use anti-freeze in your engine coolant, make sure your through bhull seacocks are in good condition and valve closes Inboard diesels basically will keep going if you give them clean water free diesel, simple baya filter will help there and discipline handling the fuel. Who puts anti-freeze in an outboard and where is the seacock? What exactly is difficult about keeping an outboard going? I have to belive you are still under the impression outboard design is the same as it was 30yrs ago.

Hobbyhorsing of any multihull in heavy seas will affect your outboards. Some are designed to run even when submerged but we all kniw it will only be matter of time before damage occurs. The position of the outboard propeller has tobe in the ideal drive position to be efficient, fuel and power wise. Only efficient o flat seas. Once up and down movement starts in the waves imagine the poor efficiency. Inboard propellers, typically on saildrives mounted far from stern in front of the rudders, will remain efficient even in heavy seas. The flow of water from the propellers will make the rudders, steering, much more efficient to. And if it's that bad, are your diesel air intakes going under water? I've never came close to putting the outboard underwater. With the outboard that steers, it's even better than relying on propwash over the rudders. It even steers in reverse. Of course, if you are talking twin engines, it's irrelevant as standard procedure is to leave the helm centered and just work the gears/throttles.

Autopilot on rudders used in combination with outboards simply dont wirk as smooth as they do with inboards. How so?

Sure outboards will be best for the weekend cruiser because marine diesels have to run. This sentance doesn't even make sense. Could you clarify what you are trying to say. All engines are better off with regular use. [/QUOTE]

As it turns out we are actually considering a Catalac 10M. I'm struggling with the fact it needs new saildrive seals and motor mounts. For the cost to have those replaced (And still have a 20yr old drivetrain) I could get a brand new outboard. And that's regular maintenance recommended every 7yrs. Our current boat has an 8yr old outboard that still works flawlessly with nothing but normal maintenance. Pending the results of the survey, will probably proceed anyway but definetly a drawback. Unfortuantely, the design is not conducive to retrofitting outboards.

I love your prowess for healthy debate. I hope I assisted you in formulating your views much clearer. On one point please educate me on the autopilot you use with your outboards.


Sent from my iPad using Cruisers Sailing Forum

[valhalla360]

[QUOTE=Goosebumps;1815597]

Originally Posted by valhalla360

Wow there is a lot of mis-information here.




I love your prowess for healthy debate. I hope I assisted you in formulating your views much clearer. On one point please educate me on the autopilot you use with your outboards.


Sent from my iPad using Cruisers Sailing Forum

When motoring the outboard is tied to the rudders.

When sailing, you have the option to lift it clear of the water.

The autopilot doesn't know the difference. There is no noticeable difference in the effort required to steer.

[44'cruisingcat]

Originally Posted by Goosebumps

I love your prowess for healthy debate. I hope I assisted you in formulating your views much clearer. On one point please educate me on the autopilot you use with your outboards.

I have a Simrad. People I know with outboard powered cat's have various brands of autopilots, including Garmin, Raymarine, Coursemaster....

There is absolutely no reason an autopilot would have any more difficulty in steering an outboard powered cat. In fact, I'd argue that the absence of turbulence caused by propeller and saildrive, would allow an outboard powered cat to steer BETTER, particularly under sail, if there's any difference at all.

[Snowgoose35]

I am considering a swap from Yanmar 3GM30 inboard to a Yamaha high thrust outboard this winter. On my Prout I have a central single diesel with Sillette outdrive which already lifts and steers but requires more maintenance than anything else on the boat and frankly is a poor design and very problematic. Worse though is the fact that someone in my boat's history decided to cram the 3GM in to an engine bay designed for a 2GM. The extra 10 horses is probably better (not that's I'd know as I never had the lower powered option) but on a 3500kg (7000b) boat its rather over powered. Maintenance is an absolute nightmare - there is simply zero room to do anything - perhaps 1 inch at the front before the bulkhead and 2 inches each side...

Its an old engine now (over 20 years) and I've spent a fortune keeping it going but still it continues to have issues.

If I swap to an outboard, which can sit where the outdrive leg now sits - that is very low in the centre nacelle, deep in the water, 4 feet forward of the stern - I see the following advantages (please correct me if I'm wrong and add to the list)

I save 200 kg in weight right at the back of the boat - (the outboard weighs in at almost the same as the stern drive thus the diesel and gearbox and ancillary weight is gone) which should vastly improve sailing and thus mean less engine use anyway...

I can manoeuvre better as the out board steers 45 degrees each way whilst the stern drive only 20 degrees.

It will be much quieter (even with 30 kg of lead and foam insulation the diesel is too loud for normal speech in the cockpit)

It will be much easier to work on and if it fails could be swapped out in under an hour (remote control cables being the longer part of the swap than simply unbolting from the back of the engine pod)

A huge new storage locker where the engine used to be.

The cons as I can see are ; slightly more expensive on fuel, slightly less power / thrust than the diesel but then perhaps offset by losing so much weight, perhaps a slight reduction in value of the boat and some care needed in storing petrol on board.

Do outboards all need a fresh water flush after use though? As a cruising boat this might impinge on my fresh water supply if I need to do that every time I run it. (I use an electric outboard on my dinghy so have never actually used a petrol outboard so I'm not sure if this is common to all modern 4 strokes)

The Prout Snowgoose was designed for an inboard diesel but with the centre nacelle engine pod it seems almost uniquely designed for such a conversion as there are none of the where to mount, will it sit deep in the water etc issues.

Any advice, opinions. (Please note I have not mentioned which power of outboard I am considering so as to avoid all the"you'll never have enough power to push in to 300 foot waves in hurricane force winds when you have to comments that I've found in a lot of these threads)

[valhalla360]

Originally Posted by Snowgoose35

I am considering a swap from Yanmar 3GM30 inboard to a Yamaha high thrust outboard this winter. On my Prout I have a central single diesel with Sillette outdrive which already lifts and steers but requires more maintenance than anything else on the boat and frankly is a poor design and very problematic. Worse though is the fact that someone in my boat's history decided to cram the 3GM in to an engine bay designed for a 2GM. The extra 10 horses is probably better (not that's I'd know as I never had the lower powered option) but on a 3500kg (7000b) boat its rather over powered. Maintenance is an absolute nightmare - there is simply zero room to do anything - perhaps 1 inch at the front before the bulkhead and 2 inches each side...

Its an old engine now (over 20 years) and I've spent a fortune keeping it going but still it continues to have issues.

If I swap to an outboard, which can sit where the outdrive leg now sits - that is very low in the centre nacelle, deep in the water, 4 feet forward of the stern - I see the following advantages (please correct me if I'm wrong and add to the list)

I save 200 kg in weight right at the back of the boat - (the outboard weighs in at almost the same as the stern drive thus the diesel and gearbox and ancillary weight is gone) which should vastly improve sailing and thus mean less engine use anyway.. While it will cut weight, I wouldn't count on a huge improvement in sailing. In terms of the overall boat, it's really not that much and then you have to avoid filling that extra hatch.

I can manoeuvre better as the out board steers 45 degrees each way whilst the stern drive only 20 degrees.

It will be much quieter (even with 30 kg of lead and foam insulation the diesel is too loud for normal speech in the cockpit) Probably true. While cruising we sit on opposite sides of the cockpit and converse without having to raise our voices.

It will be much easier to work on and if it fails could be swapped out in under an hour (remote control cables being the longer part of the swap than simply unbolting from the back of the engine pod) True!!!

A huge new storage locker where the engine used to be. True but there goes the weight savings.

The cons as I can see are ; slightly more expensive on fuel, slightly less power / thrust than the diesel but then perhaps offset by losing so much weight, perhaps a slight reduction in value of the boat and some care needed in storing petrol on board. With the newer 4 stroke motors, the fuel consumption is not much more. Get a work boat prop (low propeller pitch) and you should have plenty of thrust. Also go for the extra long leg if you can get it. It may or may not impact the value of the boat. If it's a quality installation, I wouldn't expect much of an issue. If it looks cobbled together, then yes.

Do outboards all need a fresh water flush after use though? As a cruising boat this might impinge on my fresh water supply if I need to do that every time I run it. (I use an electric outboard on my dinghy so have never actually used a petrol outboard so I'm not sure if this is common to all modern 4 strokes) You don't need to flush on a daily basis. We've never flushed off the boats fresh water supply. Currently we are on the Great Lakes so it's a non-issue but when we were going the Great Loop we tried to flush it once a week when we were in a marina. Pretty simple to lay on the back deck and reach down to hook up the ear muffs.

The Prout Snowgoose was designed for an inboard diesel but with the centre nacelle engine pod it seems almost uniquely designed for such a conversion as there are none of the where to mount, will it sit deep in the water etc issues.

Any advice, opinions. (Please note I have not mentioned which power of outboard I am considering so as to avoid all the"you'll never have enough power to push in to 300 foot waves in hurricane force winds when you have to comments that I've found in a lot of these threads) There is no right answer and there is some debate among Gemini owners (similar size to your boat) but the most common recommendation is 25hp. 10-15hp will work fine 95% of the time but on the rare situations when you do have to fight into a really strong headwind/waves, the extra thrust is nice. They originally came with 30-40hp outboards.

See above

[tomfl]

Just a quick note that outboards with carbs like a Yamaha 9.9HP get about the same fuel economy as something like a 25HP outboard with electronic fuel injection.

Problem is finding an high thrust outboard with extra long shaft that has elephant ear props.

[valhalla360]

Originally Posted by tomfl

Just a quick note that outboards with carbs like a Yamaha 9.9HP get about the same fuel economy as something like a 25HP outboard with electronic fuel injection.

Problem is finding an high thrust outboard with extra long shaft that has elephant ear props.

20" shafts are easy to come by. If you feel the need for the 25" shaft, there are extension kits available.

I would highly recommend the fuel injected 25hp. (assuming that is consitent with your power needs)

[Snowgoose35]

Who makes a fuel injected 25hp? Both Yamaha and Honda websites talk about carbs in their specs for their 25s ...

[valhalla360]

Originally Posted by Snowgoose35

Who makes a fuel injected 25hp? Both Yamaha and Honda websites talk about carbs in their specs for their 25s ...

Our 2007 Mercury is fuel injected. I assume they are still making them.

[EllisElectric]

What are the advantages or disadvantages of using Kerosene outboards by Yamaha. The outboards could be mounted along the sides of vessel instead of the aft.