Home |
Search |
Today's Posts |
|
#2
posted to rec.boats.building
|
|||
|
|||
Air cooled two stroke as inboard?
On Sun, 23 Aug 2009 10:20:03 +0700, Bruce In Bangkok
wrote: On Sat, 22 Aug 2009 21:04:51 -0400, wrote: On Sun, 23 Aug 2009 07:24:30 +0700, Bruce In Bangkok wrote: On Sat, 22 Aug 2009 10:36:47 -0400, wrote: On Sat, 22 Aug 2009 09:32:43 -0400, "mmc" wrote: "Andrew Erickson" wrote in message ... In article , wrote: On Fri, 21 Aug 2009 11:16:09 -0400, Andrew Erickson wrote: In article , wrote: On Thu, 20 Aug 2009 20:21:25 -0700 (PDT), Robin wrote: I had a brainwave the other day about putting a small (300cc) aircooled two stroke as an inboard in a small wooden boat. With adequate air circulation can anyone see any potential issues here? I would build the boat with this purpose in mind so adapting something to fit would not be a problem. Robin How are you going to cool it adequately? I would assume, for an air-cooled engine, that's where the "adequate air circulation" comes in to play. One would probably have to be a bit careful not to push the engine too hard too long, as well, since many applications for these engines are not at steady high output. (There are exceptions--ultralight aircraft engines for one example.) I don't see any inherent insurmountable objections to doing this. A speed reduction of some sort would be nearly essential, of course, or else using a jet drive. Small two stroke engines in general tend to be inefficient and noisy and smelly and a bit temperamental, although the newer ones are vastly improved over older designs. On the other hand, they are lightweight and generally unaffected by being off level (limited mostly by the particular carburetor design), which can be advantages for use in a small boat. It's not as though there aren't a great many jet skis and boats with older outboards zipping around just fine with two stroke engines every day. Granted, most of these are water cooled, but still... There is a world of difference between a water cooled two-stroke, and an aircooled two-stroke, especially in a confined space. When I ask about cooling, it's because there will be a need for BIG fans to make this work. Air cooled motorcycles tend to overheat sitting in traffic. They need to keep moving to maintain reasonable temps. "Police Special" Harleys have a detuned and lower compression engine for this reason. Just being outside in open air is not enough. Put an engine like that as an inboard on a boat and you are in for trouble. It really needs to be addressed. I'm not sure it can be done practically. Snowmobile engines traditionally were air cooled two stroke engines (although more recently four stroke engines and liquid cooling have become common), and generally inside cowlings, and they generally manage to avoid overheating just fine. Likewise, chainsaw engines don't tend to overheat all the time, despite often being run rather hard. It's a question of the specific engine design (presumably based on the intended application), not a problem common to all two strokes. You are quite correct, though, that the original poster (should they attempt the conversion) should give some careful consideration to cooling. I don't think the end result would ever be an ideal boat motor, but I also think it could be perfectly adequate and probably a lot of fun if you're into that sort of thing. -- Andrew Erickson "He is no fool who gives what he cannot keep to gain that which he cannot lose." -- Jim Elliot Some small outboards were/are air cooled as well like the Sears Game Fishers, I think up to 5hp. Not even remotely the same thing as mounting an air cooled engine as an inboard. Err - the Honda 2 H.P. is an air cooled engine. Apparently has no problems with its cooling system. I had, and several friends presently have, air cooled 2-stroke, portable generators. Millions of lawn mowers are air cooled. I could go on but why bother. the O.P. already mentioned that he could foresee the problem of adequate air supply. What in the world is going to be a problem? Cheers, Bruce (bruceinbangkokatgmaildotcom) I have already said that air cooled engines work IN SOME APPLICATIONS, including small outboards. Where they don't work well is in enclosed spaces on a small boat. Providing adequate air moving past it WILL be a problem. BTW, the Honda outboard is a 4-stroke, dummy. Err... the guy said "putting a small (300cc) aircooled two stroke as an inboard in a small wooden boat". He didn't talk about enclosing it or anything else. In fact he says "With adequate air circulation can anyone see any potential issues here?". Given his specifications (small boat, small engine) and that he has stated that he is prepared to cope with air circulation problems what are your concerns? That he, like you, has grossly underestimated this issue. In reference to the Honda, do you really think that the cooling requirements on a two stroke engine is different from that on a four stroke? Absolutely. Cheers, Bruce (bruceinbangkokatgmaildotcom) |
#3
posted to rec.boats.building
|
|||
|
|||
Air cooled two stroke as inboard?
Err... the guy said "putting a small (300cc) aircooled two stroke as an inboard in a small wooden boat". He didn't talk about enclosing it or anything else. In fact he says "With adequate air circulation can anyone see any potential issues here?". Given his specifications (small boat, small engine) and that he has stated that he is prepared to cope with air circulation problems what are your concerns? That he, like you, has grossly underestimated this issue. In reference to the Honda, do you really think that the cooling requirements on a two stroke engine is different from that on a four stroke? Absolutely. Small gas engines of the utility variety ("lawn mower"engines) have long been used as inboard engines in small wooden boats. Up here in the Pacific NW USA, a local traditional boat called the Poulsbo (or Young) boat was frequently powered with an air-cooled Wisconsin or B&S single lunger. The Poulsbo boat usually was between 16 and 18 feet long and was open. The motor hung out in the breeze. These air-cooled four stroke engines were relatively slow turning and the noise was only mildly objectionable. A modern air-cooled two stroke inboard would need to spin at a much higher speed and would create quite a racket. Would a small, 300cc, two stroke inboard work? Sure but the effort would be high and results may not be satisfactory. If the OP really wants a small boat inboard, look for a vintage four-stroke. It might be more practical to design/redesign/modify the boat for an outboard. A few of the surviving Poulsbo boats have been modified to use an outboard, either on a bracket on the stern (easiest) or in a well (elegant but lots of work). |
#4
posted to rec.boats.building
|
|||
|
|||
Air cooled two stroke as inboard?
On Sun, 23 Aug 2009 08:16:27 -0400, wrote:
On Sun, 23 Aug 2009 10:20:03 +0700, Bruce In Bangkok wrote: On Sat, 22 Aug 2009 21:04:51 -0400, wrote: On Sun, 23 Aug 2009 07:24:30 +0700, Bruce In Bangkok wrote: On Sat, 22 Aug 2009 10:36:47 -0400, wrote: On Sat, 22 Aug 2009 09:32:43 -0400, "mmc" wrote: "Andrew Erickson" wrote in message ... In article , wrote: On Fri, 21 Aug 2009 11:16:09 -0400, Andrew Erickson wrote: In article , wrote: On Thu, 20 Aug 2009 20:21:25 -0700 (PDT), Robin wrote: I had a brainwave the other day about putting a small (300cc) aircooled two stroke as an inboard in a small wooden boat. With adequate air circulation can anyone see any potential issues here? I would build the boat with this purpose in mind so adapting something to fit would not be a problem. Robin How are you going to cool it adequately? I would assume, for an air-cooled engine, that's where the "adequate air circulation" comes in to play. One would probably have to be a bit careful not to push the engine too hard too long, as well, since many applications for these engines are not at steady high output. (There are exceptions--ultralight aircraft engines for one example.) I don't see any inherent insurmountable objections to doing this. A speed reduction of some sort would be nearly essential, of course, or else using a jet drive. Small two stroke engines in general tend to be inefficient and noisy and smelly and a bit temperamental, although the newer ones are vastly improved over older designs. On the other hand, they are lightweight and generally unaffected by being off level (limited mostly by the particular carburetor design), which can be advantages for use in a small boat. It's not as though there aren't a great many jet skis and boats with older outboards zipping around just fine with two stroke engines every day. Granted, most of these are water cooled, but still... There is a world of difference between a water cooled two-stroke, and an aircooled two-stroke, especially in a confined space. When I ask about cooling, it's because there will be a need for BIG fans to make this work. Air cooled motorcycles tend to overheat sitting in traffic. They need to keep moving to maintain reasonable temps. "Police Special" Harleys have a detuned and lower compression engine for this reason. Just being outside in open air is not enough. Put an engine like that as an inboard on a boat and you are in for trouble. It really needs to be addressed. I'm not sure it can be done practically. Snowmobile engines traditionally were air cooled two stroke engines (although more recently four stroke engines and liquid cooling have become common), and generally inside cowlings, and they generally manage to avoid overheating just fine. Likewise, chainsaw engines don't tend to overheat all the time, despite often being run rather hard. It's a question of the specific engine design (presumably based on the intended application), not a problem common to all two strokes. You are quite correct, though, that the original poster (should they attempt the conversion) should give some careful consideration to cooling. I don't think the end result would ever be an ideal boat motor, but I also think it could be perfectly adequate and probably a lot of fun if you're into that sort of thing. -- Andrew Erickson "He is no fool who gives what he cannot keep to gain that which he cannot lose." -- Jim Elliot Some small outboards were/are air cooled as well like the Sears Game Fishers, I think up to 5hp. Not even remotely the same thing as mounting an air cooled engine as an inboard. Err - the Honda 2 H.P. is an air cooled engine. Apparently has no problems with its cooling system. I had, and several friends presently have, air cooled 2-stroke, portable generators. Millions of lawn mowers are air cooled. I could go on but why bother. the O.P. already mentioned that he could foresee the problem of adequate air supply. What in the world is going to be a problem? Cheers, Bruce (bruceinbangkokatgmaildotcom) I have already said that air cooled engines work IN SOME APPLICATIONS, including small outboards. Where they don't work well is in enclosed spaces on a small boat. Providing adequate air moving past it WILL be a problem. BTW, the Honda outboard is a 4-stroke, dummy. Err... the guy said "putting a small (300cc) aircooled two stroke as an inboard in a small wooden boat". He didn't talk about enclosing it or anything else. In fact he says "With adequate air circulation can anyone see any potential issues here?". Given his specifications (small boat, small engine) and that he has stated that he is prepared to cope with air circulation problems what are your concerns? That he, like you, has grossly underestimated this issue. Perhaps he has but I put a 5 H.P. Briggs & Stratton in a 15 ft. boat some 60 years ago so I, at least, have some experience in the matter. Frankly a point that you don't seem to have considered, that of what to do with the exhaust, is probably the most likely to cause problems - after the problem of how to bore a straight hole for the shaft log is solved anyway :-) Cheers, Bruce (bruceinbangkokatgmaildotcom) |
#5
posted to rec.boats.building
|
|||
|
|||
Air cooled two stroke as inboard?
On Mon, 24 Aug 2009 07:01:26 +0700, Bruce In Bangkok
wrote: On Sun, 23 Aug 2009 08:16:27 -0400, wrote: On Sun, 23 Aug 2009 10:20:03 +0700, Bruce In Bangkok wrote: On Sat, 22 Aug 2009 21:04:51 -0400, wrote: On Sun, 23 Aug 2009 07:24:30 +0700, Bruce In Bangkok wrote: On Sat, 22 Aug 2009 10:36:47 -0400, wrote: On Sat, 22 Aug 2009 09:32:43 -0400, "mmc" wrote: "Andrew Erickson" wrote in message ... In article , wrote: On Fri, 21 Aug 2009 11:16:09 -0400, Andrew Erickson wrote: In article , wrote: On Thu, 20 Aug 2009 20:21:25 -0700 (PDT), Robin wrote: I had a brainwave the other day about putting a small (300cc) aircooled two stroke as an inboard in a small wooden boat. With adequate air circulation can anyone see any potential issues here? I would build the boat with this purpose in mind so adapting something to fit would not be a problem. Robin How are you going to cool it adequately? I would assume, for an air-cooled engine, that's where the "adequate air circulation" comes in to play. One would probably have to be a bit careful not to push the engine too hard too long, as well, since many applications for these engines are not at steady high output. (There are exceptions--ultralight aircraft engines for one example.) I don't see any inherent insurmountable objections to doing this. A speed reduction of some sort would be nearly essential, of course, or else using a jet drive. Small two stroke engines in general tend to be inefficient and noisy and smelly and a bit temperamental, although the newer ones are vastly improved over older designs. On the other hand, they are lightweight and generally unaffected by being off level (limited mostly by the particular carburetor design), which can be advantages for use in a small boat. It's not as though there aren't a great many jet skis and boats with older outboards zipping around just fine with two stroke engines every day. Granted, most of these are water cooled, but still... There is a world of difference between a water cooled two-stroke, and an aircooled two-stroke, especially in a confined space. When I ask about cooling, it's because there will be a need for BIG fans to make this work. Air cooled motorcycles tend to overheat sitting in traffic. They need to keep moving to maintain reasonable temps. "Police Special" Harleys have a detuned and lower compression engine for this reason. Just being outside in open air is not enough. Put an engine like that as an inboard on a boat and you are in for trouble. It really needs to be addressed. I'm not sure it can be done practically. Snowmobile engines traditionally were air cooled two stroke engines (although more recently four stroke engines and liquid cooling have become common), and generally inside cowlings, and they generally manage to avoid overheating just fine. Likewise, chainsaw engines don't tend to overheat all the time, despite often being run rather hard. It's a question of the specific engine design (presumably based on the intended application), not a problem common to all two strokes. You are quite correct, though, that the original poster (should they attempt the conversion) should give some careful consideration to cooling. I don't think the end result would ever be an ideal boat motor, but I also think it could be perfectly adequate and probably a lot of fun if you're into that sort of thing. -- Andrew Erickson "He is no fool who gives what he cannot keep to gain that which he cannot lose." -- Jim Elliot Some small outboards were/are air cooled as well like the Sears Game Fishers, I think up to 5hp. Not even remotely the same thing as mounting an air cooled engine as an inboard. Err - the Honda 2 H.P. is an air cooled engine. Apparently has no problems with its cooling system. I had, and several friends presently have, air cooled 2-stroke, portable generators. Millions of lawn mowers are air cooled. I could go on but why bother. the O.P. already mentioned that he could foresee the problem of adequate air supply. What in the world is going to be a problem? Cheers, Bruce (bruceinbangkokatgmaildotcom) I have already said that air cooled engines work IN SOME APPLICATIONS, including small outboards. Where they don't work well is in enclosed spaces on a small boat. Providing adequate air moving past it WILL be a problem. BTW, the Honda outboard is a 4-stroke, dummy. Err... the guy said "putting a small (300cc) aircooled two stroke as an inboard in a small wooden boat". He didn't talk about enclosing it or anything else. In fact he says "With adequate air circulation can anyone see any potential issues here?". Given his specifications (small boat, small engine) and that he has stated that he is prepared to cope with air circulation problems what are your concerns? That he, like you, has grossly underestimated this issue. Perhaps he has but I put a 5 H.P. Briggs & Stratton in a 15 ft. boat some 60 years ago so I, at least, have some experience in the matter. Frankly a point that you don't seem to have considered, that of what to do with the exhaust, is probably the most likely to cause problems - after the problem of how to bore a straight hole for the shaft log is solved anyway :-) Cheers, Bruce (bruceinbangkokatgmaildotcom) Once again, a 4-stroke Briggs and Stratton is a far cry from a 300 cc 2-stroke. It runs slower, cooler and quieter. B&S is a known quantity. We know that B&S 4-stroke engines are engineered to be used in stationary machines, where there is not a rush of wind blowing past them. As far as considering exhaust problems, I don't need to. I also don't need to worry about what color to paint the boat, or what prop to use. Why would I need to consider those things when I already dismissed the whole idea on other grounds? |
Reply |
Thread Tools | Search this Thread |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Forum | |||
4 stroke outboard for 2 stroke design - 14 ft skiff | Boat Building | |||
Converting air cooled to water cooled...maybe | Boat Building | |||
Honda 50 4 stroke vs Yamaha 60 4 stroke | General | |||
2004 9.9 Mercury - 2 stroke or 4 stroke? | General | |||
Outboard HP - 2-Stroke vs. 4-Stroke - no such thing as FINAL | Cruising |