We're looking closely at a 1976 Islander 36 on the Bay. It appears sound and well cared for. It was repowered about 3 years ago with a 2000 series Vovlo Penta at only 18 hp. This would seem marginal but I would appreciate any personal experience with the Islander. Assuming that hull speed could be reached with the motor, does smaller imply an ongoing strain? The bay does have currents to consider. Much appreciated
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I think that is way too small.
Jim: I think that engine is way too small for that size boat. Think about the Yanmar formula (1hp for each 500 pounds of boat). I must assume that you are probably in the 14-17,000 lb range which would indicate 28+ HP. The PO either did not care about motoring or went cheap. Also there is not a great following for the Volvo engines on this website. Expensive parts and excessive oil consumption are two major complaints.
Jim: I think that engine is way too small for that size boat. Think about the Yanmar formula (1hp for each 500 pounds of boat). I must assume that you are probably in the 14-17,000 lb range which would indicate 28+ HP. The PO either did not care about motoring or went cheap. Also there is not a great following for the Volvo engines on this website. Expensive parts and excessive oil consumption are two major complaints.
Course horse for current currents...
Jim, Steve is right on. The current at the Gate can be above five knots at a spring tidal current. That is mainly, but not restricted to, between Mile Rock ( the candy cane on the south side, two nautical miles from the center range) and the Gate.
Jim, Steve is right on. The current at the Gate can be above five knots at a spring tidal current. That is mainly, but not restricted to, between Mile Rock ( the candy cane on the south side, two nautical miles from the center range) and the Gate.
motoring through currents
I've always thought that currents have no effect on motoring. If your only doing 2.5 knots COG but you are going against a 5 knot current, then you are reaching hull speed for an approx 36' boat. Would you have to go with a hugh engine to be able to increase your COG any more then that? In otherwords, if you can reach hull speed without a current, can't you reach it with a current too no matter the size of engine? Now I understand trying to motor against the wind is different. I've tried motoring against 30 knots of wind and only reaching 2.5 knots with very choppy 4' waves.
I've always thought that currents have no effect on motoring. If your only doing 2.5 knots COG but you are going against a 5 knot current, then you are reaching hull speed for an approx 36' boat. Would you have to go with a hugh engine to be able to increase your COG any more then that? In otherwords, if you can reach hull speed without a current, can't you reach it with a current too no matter the size of engine? Now I understand trying to motor against the wind is different. I've tried motoring against 30 knots of wind and only reaching 2.5 knots with very choppy 4' waves.
Good thoughts, Franklin
Dealing with current through the Golden Gate is surely a matter of timing your passage or using the back currents at Baker Beach or Pt. Diablo. Anyone who tries to buck the currents through the Gate is asking for trouble and delayed passages. We have a C34 with a 21 hp motor. An islander 36 with the right prop and an 18 hp motor is pretty much in the same boat, given similar waterline lengths. If you like the rest of the boat, don't sweat the engine size. Many might consider this heresy, but learn to sail the boat and use the currents. Rare will be time time that a 50 hp motor would get you out of trouble that an 18 hp wouldn't. OTOH, I agree with Steve about the manufacturer of the engine.
Dealing with current through the Golden Gate is surely a matter of timing your passage or using the back currents at Baker Beach or Pt. Diablo. Anyone who tries to buck the currents through the Gate is asking for trouble and delayed passages. We have a C34 with a 21 hp motor. An islander 36 with the right prop and an 18 hp motor is pretty much in the same boat, given similar waterline lengths. If you like the rest of the boat, don't sweat the engine size. Many might consider this heresy, but learn to sail the boat and use the currents. Rare will be time time that a 50 hp motor would get you out of trouble that an 18 hp wouldn't. OTOH, I agree with Steve about the manufacturer of the engine.
Use the sails in 30 knot winds
Currents are not the issue for all the above reasons. The wind will be something to contend with if you insist on not putting up any sail. In a 30 knot wind you should be reefed but you can make hull speed! Then the real issue is how well does she point.
Currents are not the issue for all the above reasons. The wind will be something to contend with if you insist on not putting up any sail. In a 30 knot wind you should be reefed but you can make hull speed! Then the real issue is how well does she point.
Why are people in a hurry when they
go sailing? Or perhaps when they finish sailing and want to go home? If you are doing something you enjoy, why hurry? 18 HP with the right prop will get you home and into the slip. A bigger engine will just burn more fuel and cost more generally.
go sailing? Or perhaps when they finish sailing and want to go home? If you are doing something you enjoy, why hurry? 18 HP with the right prop will get you home and into the slip. A bigger engine will just burn more fuel and cost more generally.
Try 50 miles down stream with no wind.....
Try 50 miles down stream with no wind and an incoming tide. Believe me this is no fun. You can be pounding into this chop and going 3-4 kts with an underpowered motor. Trying to make in back into the SF bay with a couple of kts. of ebb tide may leave you outside the gate for a couple of hours in horrible weather. We are NOT all ancient mariners with no time schedules. A properly sized engine is important in the bay. The Islander 36 is a great boat, just keep looking.
Try 50 miles down stream with no wind and an incoming tide. Believe me this is no fun. You can be pounding into this chop and going 3-4 kts with an underpowered motor. Trying to make in back into the SF bay with a couple of kts. of ebb tide may leave you outside the gate for a couple of hours in horrible weather. We are NOT all ancient mariners with no time schedules. A properly sized engine is important in the bay. The Islander 36 is a great boat, just keep looking.
Steve
Please help me to understand this? HOW can a a few more HP help you pass hull speed? Hull speed is applied to your speed through the water, not speed over land. If you are trying to buck a 4 knot current and your hull speed is only 7 knots, your only going to get a COG of 3 knots unless you got a 700hp engine. If I am wrong, please explain to me how.
Please help me to understand this? HOW can a a few more HP help you pass hull speed? Hull speed is applied to your speed through the water, not speed over land. If you are trying to buck a 4 knot current and your hull speed is only 7 knots, your only going to get a COG of 3 knots unless you got a 700hp engine. If I am wrong, please explain to me how.
Cog - backeddies??
He must have meant 'SOG' but the trigger-finger was too fast in attempt to be an 'expert'. Nah, I have indeed been a 'purist' willing when a naive kid, an unwilling one many times...;-) Stu, those backeddies in a river with a kayak are like an elevator, not in these dangerous channels that take you in-between rocks, shoals, then spit you out into the main current going the opposite direction, it just doesn't work like that; sounds good though. Bill, the wind is coming into the Gate to get you home 90 % of the time, but there are shoals, fog that descends quickly, freighters, fishing boats, bouys, and the fickle currents of the north and south towers that make it nearly impossible to sail at the wrong time. I ahve tacked through there, many times, and chances are you could make it or head back out to sea.A smaller engine will be okay around the bay, but there could be that time when you need the horseposer to 'claw' your way out of a hole, and I have seen those times. No one should play 'Old Man of the Sea' here and hand out information that could cause someone their life. In the clipper days, the ships would at times go out two or three times with the tide before they finally found some wind, towing the mother ship with long-boats through straits, and away from shoals. A powerful engine with a true pitch three-blade is the only way to go, and you can STILL get into trouble.
He must have meant 'SOG' but the trigger-finger was too fast in attempt to be an 'expert'. Nah, I have indeed been a 'purist' willing when a naive kid, an unwilling one many times...;-) Stu, those backeddies in a river with a kayak are like an elevator, not in these dangerous channels that take you in-between rocks, shoals, then spit you out into the main current going the opposite direction, it just doesn't work like that; sounds good though. Bill, the wind is coming into the Gate to get you home 90 % of the time, but there are shoals, fog that descends quickly, freighters, fishing boats, bouys, and the fickle currents of the north and south towers that make it nearly impossible to sail at the wrong time. I ahve tacked through there, many times, and chances are you could make it or head back out to sea.A smaller engine will be okay around the bay, but there could be that time when you need the horseposer to 'claw' your way out of a hole, and I have seen those times. No one should play 'Old Man of the Sea' here and hand out information that could cause someone their life. In the clipper days, the ships would at times go out two or three times with the tide before they finally found some wind, towing the mother ship with long-boats through straits, and away from shoals. A powerful engine with a true pitch three-blade is the only way to go, and you can STILL get into trouble.
Cult Classic
Islander 36’s are enjoying a resurgence of popularity here in San Francisco Bay. Why not pose your question to the experts? (http://www.islander36.org/) Eighteen HP might not be a lot by today’s standards, but it just might be the standard engine for that particular boat. Steve has a good point concerning sufficient power. Motoring out of the Delta against a flood and headwind is a real PITA, especially Middle Ground – Port Chicago. (By the way, we’ll be in the Delta first week of August). Our strategy has always been to ride the tide even if means leaving at odd hours. In regards to the Golden Gate, The local knowledge has always been to go inside to Baker Beach on the south side or Bonita Cove – Pt. Diablo on the North. I prefer the north side as you maintain relief further and it seems that all the gains you make at Baker Beach get taken away by the South Tower Demon. Another reason why I like the North is the ebb flushes out the ship channel to the light bucket and south, so when coming back in, we go for Muir beach first, then south through the Bonita Channel. We avoid the current most of the way and only spend a short time in the washing machine at Pt. Bonita.
Islander 36’s are enjoying a resurgence of popularity here in San Francisco Bay. Why not pose your question to the experts? (http://www.islander36.org/) Eighteen HP might not be a lot by today’s standards, but it just might be the standard engine for that particular boat. Steve has a good point concerning sufficient power. Motoring out of the Delta against a flood and headwind is a real PITA, especially Middle Ground – Port Chicago. (By the way, we’ll be in the Delta first week of August). Our strategy has always been to ride the tide even if means leaving at odd hours. In regards to the Golden Gate, The local knowledge has always been to go inside to Baker Beach on the south side or Bonita Cove – Pt. Diablo on the North. I prefer the north side as you maintain relief further and it seems that all the gains you make at Baker Beach get taken away by the South Tower Demon. Another reason why I like the North is the ebb flushes out the ship channel to the light bucket and south, so when coming back in, we go for Muir beach first, then south through the Bonita Channel. We avoid the current most of the way and only spend a short time in the washing machine at Pt. Bonita.
The question is whether or not ......
Franklin: The question is weather or not you will ever reach hull speed. When you are fighting the wind and the current (maybe add in some chop) you will be hard pressed to keep the boat pointed in the direction that you are going. It is a lot different motoring/sailing through constricted water ways than in the open pond. Our Hunter 31 often would exceed hull speed but it had a 18 hp engine with a 9500 lb boat. When we were going against the tide we would often be knocked back to 4-5 kts going against it. This is why they want you to have some reserve power to assist you when fighting the tides/currents.
Franklin: The question is weather or not you will ever reach hull speed. When you are fighting the wind and the current (maybe add in some chop) you will be hard pressed to keep the boat pointed in the direction that you are going. It is a lot different motoring/sailing through constricted water ways than in the open pond. Our Hunter 31 often would exceed hull speed but it had a 18 hp engine with a 9500 lb boat. When we were going against the tide we would often be knocked back to 4-5 kts going against it. This is why they want you to have some reserve power to assist you when fighting the tides/currents.
confusions about hull speed
It seems like hull speed is one of those endlessly confusing topics. Hull speed is not an absolute limit on how fast a keelboat can move through the water, it's the speed at which, when the given hull can achieve it, the hull then begins to plane and lose efficiency. Hull speed could be considered the speed of maximum economy of movement through the water for a hull with a keel. If you tow a keelboat behind some fast powerful vessel you may be able to get the hull to move through the water at 60 knots, but it will probably be bouncing around like a water skier on top of the water as it moves because the keel interferes with the efficient movement of the hull through the water at that speed. A keelboat attempting to move against (or, if you like, within) a current may need to apply extra energy to bring its SPEED OVER GROUND to the same number of knots as its theoretical hull speed in dead calm water; what you're really doing is changing the nature of the calculation by adding a current to push against. It was the style in the '80s to equip keelboats with an engine that gives just enough horsepower to get the hull up to its theoretical hull speed in calm waters; the 18hp for your islander and the 13hp for my '87 Cal 28 are typical horsepower ranges for the minimal power required for those size hulls. The trend in new boats today is to double that, perhaps because in places like SF Bay no amount of horsepower ever seems enough to keep forward progress against strong currents...
It seems like hull speed is one of those endlessly confusing topics. Hull speed is not an absolute limit on how fast a keelboat can move through the water, it's the speed at which, when the given hull can achieve it, the hull then begins to plane and lose efficiency. Hull speed could be considered the speed of maximum economy of movement through the water for a hull with a keel. If you tow a keelboat behind some fast powerful vessel you may be able to get the hull to move through the water at 60 knots, but it will probably be bouncing around like a water skier on top of the water as it moves because the keel interferes with the efficient movement of the hull through the water at that speed. A keelboat attempting to move against (or, if you like, within) a current may need to apply extra energy to bring its SPEED OVER GROUND to the same number of knots as its theoretical hull speed in dead calm water; what you're really doing is changing the nature of the calculation by adding a current to push against. It was the style in the '80s to equip keelboats with an engine that gives just enough horsepower to get the hull up to its theoretical hull speed in calm waters; the 18hp for your islander and the 13hp for my '87 Cal 28 are typical horsepower ranges for the minimal power required for those size hulls. The trend in new boats today is to double that, perhaps because in places like SF Bay no amount of horsepower ever seems enough to keep forward progress against strong currents...
Hull Speed is speed through the water
As your speed approaches hull speed the stern drops and the bow rises and in essense your boat is in a hole. More power just digs a larger hole. It takes a very large amount of power to exceed hull speed and it could probably destroy the hull. Current can add to or subtract from speed over the ground or move the boat sideways. Your course over the ground is a result of the speed and direction through the water and the speed and direction of the water. Wind changes your speed and direction through the water. Beyond the ability to reach hull speed extra power allows your to push against wind and waves. Without wind and waves a 10hp motor could probably get a 34' boat with a clean smooth bottom to near hull speed. But a 10hp motor won't push a 28' sailboat against a wind of much more than 25kts...been there done that. Our 32' boat has a 20 hp volvo that pushes us at hull speed against a 20kt wind. Timing is everything in running an inlet. If you can go with the tide or at slack tide excessive hp is not required. BTW I think the old Hunter 30' only had a 12 hp diesel as standard engine. My brothers Pacific Seacraft 25' only had an 8 hp diesel and he said that it worked well. According to "experts" it is better to run your engine at about 80% WOT. If you have a larger engine running it at 40% all of the time will cause problems.
As your speed approaches hull speed the stern drops and the bow rises and in essense your boat is in a hole. More power just digs a larger hole. It takes a very large amount of power to exceed hull speed and it could probably destroy the hull. Current can add to or subtract from speed over the ground or move the boat sideways. Your course over the ground is a result of the speed and direction through the water and the speed and direction of the water. Wind changes your speed and direction through the water. Beyond the ability to reach hull speed extra power allows your to push against wind and waves. Without wind and waves a 10hp motor could probably get a 34' boat with a clean smooth bottom to near hull speed. But a 10hp motor won't push a 28' sailboat against a wind of much more than 25kts...been there done that. Our 32' boat has a 20 hp volvo that pushes us at hull speed against a 20kt wind. Timing is everything in running an inlet. If you can go with the tide or at slack tide excessive hp is not required. BTW I think the old Hunter 30' only had a 12 hp diesel as standard engine. My brothers Pacific Seacraft 25' only had an 8 hp diesel and he said that it worked well. According to "experts" it is better to run your engine at about 80% WOT. If you have a larger engine running it at 40% all of the time will cause problems.
On the economical side of this
discussion I have found these answers: Allowing for a 30 foot water line Hull speed is 7.3 kts. and will require 27.8 hp at the prop. Reducing speed to 5.5 kts. will require 11.7 hp at the prop. So for a gain of 1.8 kts an additional 16 hp is required at a cost of 1.2 gallons of fuel per hour plus the cost of the larger power train.
discussion I have found these answers: Allowing for a 30 foot water line Hull speed is 7.3 kts. and will require 27.8 hp at the prop. Reducing speed to 5.5 kts. will require 11.7 hp at the prop. So for a gain of 1.8 kts an additional 16 hp is required at a cost of 1.2 gallons of fuel per hour plus the cost of the larger power train.
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