Inboard vs. Outboard for Cruising

[brianlara 3]

He did say that leaving the outboat off allows for 110lbs more fuel capacity if he went with inboard only. I got the impression that one option for him was a single engine...I might have been wrong there.
Appreciate your correcting me Adelie.

[Don C L]

Originally Posted by coastalexplorer

So my question is do any of you have your sailing vessel set up with both options??

nursing 2 internal combustion engines to propel my sailboat is something up with which I will not put.

[coastalexplorer]

To answer the last questions by Brianlara3 .The vessel is a coast 30. Designed by Grahame H Shannon, officially retired from his company of Avia designs. The lines drawing for it may be a stern modified Bruce Roberts Goodson design 341. Which Grahame originally drew while working with Bruce in San Diego in the 1980's? I communicate with either of them from time to time.

The hull was built cold molded in 1982 by Mr. Tim Tuulos formerly from Finland who was also a friend that I lost contact with about 1992. (If anyone has details of what happened to him I am interested to know please PM me) The hull was outfitted by the first owner George Gough by about 1985 with a 9.9 Honda. 1984 vintage... unfortunately I do not know which version and the Vancouver Honda Centre does not seem to have information that far back as to what was available.

The vessel was sold on to new owners in 1989 still with outboard; However at some point a shipyard was obviously contracted to fit a stern tube and volvo MD 17 was fitted.This was later changed to a 1972 single cylinder 12 Hp Yanmar by the time the vessel was sold in 2007. The installation of which was done in such a hacked up way that caused major damage to the interior which I had to rip out and rebuild. PO sent this Diesel to the scrap yard.

Getting back in topic... The mention of a 'Suredrive' is reference to a product designed by next Wave Marine systems Inc of Qualicum Beach, on Vancouver's Island; to take care of the design deficiency of the connection between the 2003 volvo Diesel and the MS2B transmission gear which I hope will prove more reliable. I understand Stem to Stern in Vancouver BC are now dealers. (So it is not a saildrive)

Originally and always named 'SHERA' It was the fist 'large' hull built by Tim Tuulos an artist at this class of work! registered at only 6.500 Lbs: The last hull he built 'Marijatta' is possibly still for sale: located at Ioco Yacht club asking $20,000 CDN. for those looking for a turn key racing cruising vessel check that out. the paint job is worth that!

In answer to Adelie. The Dingy is a walkerbay 8 also designed by Grahame H Shannon, We have both a 2 HP and a 1963 vintage 4.5 HP British seagull for that. Which was in deed designed to push a 25 foot waterline length hull. unfortunately even with a hypalon RIV tube This Boat does not have enough buoyancy to carry us and the 4.5HP, safely in rough water as the exhaust is too deeply immersed. We have a Garlick 2 stroke outboard motor bracket but putting two out boards on the transom for that versatility could look just a little excessive?

[brianlara 3]

Coast, I went to Sailboatdata and saw the Shannon/Roberts Coast 34.
Is yours also canoe stern? If so then a bit of a job making a support bracket.
This might interest you: A good friend of mine has a 33ft steel sloop which has done Sydney-Hobart-Adelaide & back to Sydney about 5 times. All of those trips were with a weary old Mariner 8 hp 2 stroke short shaft mounted on a transom bracket.Two years ago he upgraded to a Johnson 15hp 2 stroke and in a few weeks will be heading out to Tasmania and beyond again after 5 years inshore. The new Johnson 15 seems to push the boat at about 5 knots in still water.
Control of his motor is a real pain when stopping/anchoring.
How's them apples?

[brianlara 3]

Coast, re storage space. My boat has an outboard in a sealed & ventilated portside cockpit locker well ahead of the transom. Never cavitates.
Where a diesel would normally be I have 2 of my 4 x 120ah agm's and a truck load of power tools etc. Fwiw.

[Adelie]

Originally Posted by brianlara 3

He did say that leaving the outboat off allows for 110lbs more fuel capacity if he went with inboard only. I got the impression that one option for him was a single engine...I might have been wrong there.
Appreciate your correcting me Adelie.

If he is going to have a motor on the dinghy, then the only weight penalty is the weight of the motor mount on the stern. The questions then become what size outboard and how much fuel?

Let's say he has a 6gal tank half gone when the inboard packs it in. With 3gal motoring at 3.5-4.0kt he should have 50-60nm range in flat water.

If he keeps a 2nd 6gal tank on hand he's accepting another weight penalty of about 40lb but has 100nm or so range even if the primary tank is empty. The upside to the extra fuel is more redundancy for both the mother ship and the dinghy.

If he has an outboard for the dinghy anyway then there is no added maintenance.

[Eben]

I'll add a different perspective to the thread...

We're still relatively new to sailing, we haven't done much - but we have had our first weekend cruise last weekend.

We've got an outboard see the details here: Training Wheels – Taleisin - Adventure Machine!

Like others mentioned it's not much use when there's any reasonable amount of chop. The only use is to enter and leave the marina.

If it's calm we can push her at 6 knots with the motor. The larger HP makes a huge difference when docking as mistakes can be corrected with high thrust. Over time as our skill improves the motor size will shrink so the point where it's easy to lift on and off single handedly. That way we can store it below when things get really gnarly.

As for what to do when it's calm, well we experienced just that over the weekend. leaving the marina there was no wind, so we used the motor to get us out of the harbour till the wind picked up enough to sail. We had a great slow sail for 15 miles. On the way home we spent 9 hours sailing 27 miles. Yes it was slow, but we enjoyed it. We sailed right up to the marina entrance, started the motor and dropped the sails. No major drama...

We're not in a hurry when sailing, so it's not an issue for us. Also it's a sail boat, we sail it!

[Adelie]

Originally Posted by coastalexplorer

To answer the last questions by Brianlara3 .The vessel is a coast 30. . . . . Originally and always named 'SHERA' It was the fist 'large' hull built by Tim Tuulos an artist at this class of work! registered at only 6.500 Lbs: . . .

In answer to Adelie. The Dingy is a walkerbay 8 also designed by Grahame H Shannon, We have both a 2 HP and a 1963 vintage 4.5 HP British seagull for that. Which was in deed designed to push a 25 foot waterline length hull. unfortunately even with a hypalon RIV tube This Boat does not have enough buoyancy to carry us and the 4.5HP, safely in rough water as the exhaust is too deeply immersed. We have a Garlick 2 stroke outboard motor bracket but putting two out boards on the transom for that versatility could look just a little excessive?

OK so the Honda 9.9 is probably excessive, but the Seagull is not.

With a 25' waterline, assuming 8,000lb loaded, the 4.5hp should be able to push you at 5.75-6.5kt in flat water. This would make it suitable for light to moderate conditions.

Put the inboard back in, then ditch the Honda but keep the outboard mount to use the dinghy motor as a backup.

Even the 2hp whatever should be able to push you at 4.5-5.25kt in flat water. So good for calm or very light conditions.

[Don C L]

Originally Posted by Adelie

OK so the Honda 9.9 is probably excessive, but the Seagull is not.

With a 25' waterline, assuming 8,000lb loaded, the 4.5hp should be able to push you at 5.75-6.5kt in flat water. This would make it suitable for light to moderate conditions.

Put the inboard back in, then ditch the Honda but keep the outboard mount to use the dinghy motor as a backup.

Even the 2hp whatever should be able to push you at 4.5-5.25kt in flat water. So good for calm or very light conditions.

OK so I have an 8000# boat and I have an 8hp and I am pretty sure a 2hp will never push me at 4 knots and a 4.5 will never push me at 5 or 6 knots! In fact, my 8hp is underpowered for an auxilliary. I'd rather have the 9.9. Pretty amazing my boat was designed to use a Seagull.

[Adelie]

Originally Posted by Don C L

OK so I have an 8000# boat and I have an 8hp and I am pretty sure a 2hp will never push me at 4 knots and a 4.5 will never push me at 5 or 6 knots! In fact, my 8hp is underpowered for an auxilliary. I'd rather have the 9.9. Pretty amazing my boat was designed to use a Seagull.

Assuming 9500lb, 22.5 lwl, 25lb thrust per 1hp using Skene's graph:



In flat water the 2hp should push you at 3.75-4.5kt. Acceleration is going to take a long time though, as in 4 or 5 min to get to speed.



In flat water the 4.5hp should get you 5.0-5.75kt.



The 8hp may be under-powered but that's probably trying to buck wind and/or waves and the anemic acceleration in those conditions probably contributes the the sense that it's under-powered.



How fast can you go with the 8hp in flat water?

[Don C L]

Originally Posted by Adelie

Assuming 9500lb, 22.5 lwl, 25lb thrust per 1hp using Skene's graph:

In flat water the 2hp should push you at 3.75-4.5kt. Acceleration is going to take a long time though.

In flat water the 4.5hp should get you 5.0-5.75kt.

The 8hp may be under-powered but that's probably trying to buck wind and/or waves and the anemic acceleration in those conditions probably contributes the the sense that it's under-powered.

How fast can you go with the 8hp in flat water?

Well, far be it from me to argue with the likes of Skene's but I tend to think running the engine at full throttle just starts wasting gas.. not a lot of return on the added investment, so at about three quarter throttle I can rely on 3.5 knots. And my 2 stroke is not too frugal on gas too... so with motoring through early morning swell (if there's wind, I'm sailing), I figure on something a little over 3 mpg is doing well! So if this Evinrude ever gives up the ghost (no sign of it yet and it's a '92), and I switch to a 4-stroke 9.9 I'll let everyone know what happens! How much a boat pitches or hobby-horses has a big influence on the numbers too I bet... which can have to do with loading the boat. Oh I have the so-called "power prop" so that will have its influence too... hopefully positive!
Funny, I met the gentleman who first bought my boat in 1963. He had the Seagull in there, fired it up, headed out of Newport where she was built and then sailed her straight up to Santa Barbara non-stop in January. I thought that was pretty cool... but I am not getting a Seagull!

[coastalexplorer]

Back home again from the workshop where I have been building a foundry pattern to make a cast aluminum wedge block in the form of a hollow box with lots of angles because the stern modification that I mentioned before was to drawn as a raked curved transom 25 degrees on the centre line with a transom hung rudder. If this is a shortened version of the 341 as Bruce Roberts goodson surmised. it changed the design from 34' Canoe stern to 30'-6". transom...so what I have yet to determine is how to fit the inboard exhaust outlet and the motor bracket within the limited space.

By drilling the working face of the casting with two different bolt patterns I should be able to mount either bracket. A Garlick 71091 offshore needs a working pad space of 10 1/16" X 9 3/4" The two stroke Garlick mounting bracket could be bolted within that because its attachment is much smaller but not both at the same time of course. The strange thing is that the four previous bolt holes in the transom do not give any idea how the original was attached.

I will have to make a decision on this before building engine beds for the diesel because once it is in: it will block access to the inside stern of the vessel.

I have heard others express the opinion that during summer months the Pacific Northwest is a low wind strength area & a lot of motoring time is needed. We do a lot of long distance dinghy travel with the outboards to get in sea time while hoping to splash SHERA next spring.

[newhaul]

Originally Posted by Adelie

Assuming 9500lb, 22.5 lwl, 25lb thrust per 1hp using Skene's graph:



In flat water the 2hp should push you at 3.75-4.5kt. Acceleration is going to take a long time though, as in 4 or 5 min to get to speed.



In flat water the 4.5hp should get you 5.0-5.75kt.



The 8hp may be under-powered but that's probably trying to buck wind and/or waves and the anemic acceleration in those conditions probably contributes the the sense that it's under-powered.



How fast can you go with the 8hp in flat water?

Sorry to break it to you but here are a couple things you really should consider.
First real world trumps those graphs and formula every time.
Second what is flat water . Just because there is no wind or discernible waves. Does not mean there is no current you have to work thru.
I had a 6 HP evinrude on my boat. It was barely enough now I have an 8 HP ( both are 2 stroke) there have been times that I was wanting more power.

[thomm225]

You definitely have to know what you are are dealing with as far as small outboards.

I've had a 5hp 4 stroke on a full keel Bristol 27, and I sail where the Chesapeake Bay meets the Atlantic Ocean. (lots of different wave, tide, and wind conditons)

You simply must plan ahead. The crossing for me is about 20 miles unless I sail it against the wind then it can near double

I've crossed in about 3 hours sailing and I've crossed in 8 hours sailing.

I've crossed in 3 hours motor sailing and I have crossed in 8 hours motor sailing.

I've crossed motoring alone in 3.5 hours and I've crossed motoring in 6 hours.

If the wind is heavy NE the ocean waves have become short and steep from entering the shallow bay and can be near 5-6' right at the mouth of the creek. The motor isn't going to stay in so it's best to sail right in then deal with traffic while lowering the sails. This can get interesting for a singlehander

[newhaul]

Originally Posted by thomm225

You definitely have to know what you are are dealing with as far as small outboards.

I've had a 5hp 4 stroke on a full keel Bristol 27, and I sail where the Chesapeake Bay meets the Atlantic Ocean. (lots of different wave, tide, and wind conditons)

You simply must plan ahead. The crossing for me is about 20 miles unless I sail it against the wind then it can near double

I've crossed in about 3 hours sailing and I've crossed in 8 hours sailing.

I've crossed in 3 hours motor sailing and I have crossed in 8 hours motor sailing.

I've crossed motoring alone in 3.5 hours and I've crossed motoring in 6 hours.

If the wind is heavy NE the ocean waves have become short and steep from entering the shallow bay and can be near 5-6' right at the mouth of the creek. The motor isn't going to stay in so it's best to sail right in then deal with traffic while lowering the sails. This can get interesting for a singlehander

Thomm as a fellow single hander I have two words to make it a lot easier " lazy jacks"