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[TomF]

I wasn't sure where to post this, but since my interest is pleasure/leisure boats I put it here.
Has anyone any experience/suggestions for fitting a gasoline engine in a largish and scalish model boat (1m in length)
Like the Holt tractor engine and inline-six and inline-four[size=78%] but worry about being too noisy.[/size]


https://www.enginediy.com/products/h75-12cc-vertical-4-cylinder-ohv-gas-engine-internal-combustion-engine-tractor-engine-model-with-mechanical-speed-limit-complete-water-circulation-cooling-system?variant=42269260677334


https://www.stirlingkit.com/collections/4-stroke-engine/products/howin-l6-210-21cc-straight-six-gasoline-engine-model-building-kits-water-cooled


Thanks

[1967Brutus]

I have no direct experience with the engines you linked, but I DO own the Toyan V-8.

There is no doubt that these engines "run", somewhat, but boy.... they are basically nice discussion items, not engineered or designed to actually power something.

Don't expect any meaningful power OR service life out of them.
I was a bit appalled at design features that should be a matter of "Duh" for any engine designer worth his salt, like for example ignition plugs recessed about 6 or 7 mm into their threads, meaning a very poor ignition and combustion behaviour, a cooling system with water inlets that are WAY too small to allow proper flow for the amount of heat generated, weird and unsuitable crankshaft support bearing design, intake systems that are WAY too small and restrictive, let alone totally mismatched for symetrical fuel/air distribution, and such.

They most definitely LOOK the part, but as a functional engine capable of delivering meaningful power (and I do not even mean "all out power", just "useful" would be enough) they most likely will not satisfy.

Of course, everything can be modified or corrected, and I am sure someone with the right skills can make something nice out of them.

[TomF]

Thanks Brutus

My motivation for using a gas engine is the right one might look like something special in the right boat. Useful power would be good, but its a risk I'm willing to take.
It would be great to hear from someone who has put a gas engine in a boat.

Tom

[1967Brutus]

Thanks Brutus

My motivation for using a gas engine is the right one might look like something special in the right boat. Useful power would be good, but its a risk I'm willing to take.
It would be great to hear from someone who has put a gas engine in a boat.

Tom

Depends on what you want to know and what you consider "putting a gas engine in a boat"... I mean, fitting a 2-stroke screamer, anybody can do that but that won't be too much fun in anything that's not a speedboat, right?

Few years ago, I modified a 5 cc glow fourstroke to run on gasoline, made it run 1500 RPM and put it in a random hull, and liked it so much that I currently have just started building a decent boat for it.

Done properly (reliability and noise) it is a delight.
I can totally see an open launch with that engine of your first link (that tractor engine) to be a visual thing to behold, and the way it is set up leaves plenty options for some pretty cool engineering, such as instead of a radiator a heat exchanger and a controlled temperature, a nice bulky flywheel to get real low RPM and either a reversing gear or a controllable pitch prop to have a bit of manouverability.
But I am, looking at the reviews, pretty sure one needs to know his way around small engines in order to make something reliable out of it.

Here's my project, that back then never got past the experimental stage due to the hull being too small to make something nice out of it (which, as I said, I am doing something about right now):
https://www.youtube.com/watch?v=wfBbg45IYmk

But I can tell you beforehand that it will need a decent ignition (the one included most probably is not suitable for RC(RF noise) and you most definitely will want to get rid of that mechanical "governor"...

[TomF]

Thanks that sounds interesting, do you have any resource links for a suitable open launch?

[1967Brutus]

Thanks that sounds interesting, do you have any resource links for a suitable open launch?

Not from the top of my head no...

Just look around, and maybe you'll find a suitable hulk in the classifieds... Doesn't have to be an open launch, you can change it into one, right?

[Andyn]

I’m currently in the process of converting an NGH 9cc two stroke petrol to marine, for use in a 1m long boat. It’s going to be quite a lot of power for a hull that size. You may wish to consider a four stroke glow and convert that over

[1967Brutus]

I’m currently in the process of converting an NGH 9cc two stroke petrol to marine, for use in a 1m long boat. It’s going to be quite a lot of power for a hull that size. You may wish to consider a four stroke glow and convert that over

2-strokes are relatively easy to convert to watercooling, fourstrokes less so. But IMHO, 2-strokes just don't sound right for "non-speed" boats.

Gasoline conversions can be done, but be prepared for a LOT of tinkering with the carb.

[JimG]

I’m currently in the process of converting an NGH 9cc two stroke petrol to marine, for use in a 1m long boat. It’s going to be quite a lot of power for a hull that size. You may wish to consider a four stroke glow and convert that over

Is this the mark 1 or mark 2 version? The mark 1 is unreliable, difficult to start and set the fuel mixture due to a poor carburettor. The taper on the needle is wrong for petrol and lacks the sensitivity needed for adjustment. I have a mark 1 version and have given up on it as I could never get the needle setting right, around 3 clicks on the needle from very rich to very lean. The mark 2 has a new carburetter which is closer to a Walbro carb and is supposedly easier to set and run.
Jim

[1967Brutus]

Is this the mark 1 or mark 2 version? The mark 1 is unreliable, difficult to start and set the fuel mixture due to a poor carburettor. The taper on the needle is wrong for petrol and lacks the sensitivity needed for adjustment. I have a mark 1 version and have given up on it as I could never get the needle setting right, around 3 clicks on the needle from very rich to very lean. The mark 2 has a new carburetter which is closer to a Walbro carb and is supposedly easier to set and run.
Jim

Both are basically crap. The carb of Mark II is not all that bad, but seems to only want to run right with one prop, all others from the range are at best "acceptable". Which exact prop that is depends on manufacturing tolerances.

[Circlip]

Many of the pre 50s model boats had four stroke single cylinder petrol engines fitted. Designs by Edger T Westbury were prolific and names like 'Gannet, Channel Islands Special, Beaver and Otter'  and others were the norm and ran at well below 10K revs. O.S. certainly did a series of four strokes and were/are much quieter than than the two stoke screamers favoured by those who crave the need for speed. The slow 'Thumpers' give loads of torque.


 Regards  Ian.

[TomF]

After doing much research on suitable boats Im being drawn toward steam launches for example





There is a log build of the boat here http://www.pondboats.com/steamlaunchKailani.htm


This is the Diana Hull from hartmanmodelboats.com and is 50inches long which is about the right size.
However, the cost from the US inc shipping and duties will make it prohibitively expensive.


I did find this on ebay





Which is being sold as an icebreaker hull. It looks about the right proportions. Am I being daft at thinking this hull could be a good representation of Diana?


BTW will be fitting one of these as propulsion!





Thanks

[1967Brutus]

After doing much research on suitable boats Im being drawn toward steam launches for example





There is a log build of the boat here http://www.pondboats.com/steamlaunchKailani.htm


This is the Diana Hull from hartmanmodelboats.com and is 50inches long which is about the right size.
However, the cost from the US inc shipping and duties will make it prohibitively expensive.


I did find this on ebay





Which is being sold as an icebreaker hull. It looks about the right proportions. Am I being daft at thinking this hull could be a good representation of Diana?


BTW will be fitting one of these as propulsion!





Thanks

Going to be quite a bit of sulpting work to modify that ice breaker hull into a launch, unless you don't care about what it looks like below the waterline.

For a 50" boat, I'd say that Holt replica is more or less OK, bordering on "large" visually. A bit like a crossover between a hotrod and a launch, but I think it will be pretty nontheless.

I have no idea what kind of output that Holt Replica is capable of, but it is with a fair bit of certainty going to be "ridiculously much" and you will have to keep RPM low to very low in order to have a "scale like" speed, is my guess.
I would, at the very least, see if you can fit a heavier flywheel (like a massive one of the same dimensions) to assist the engine in running slow.

You are going to need a reversing gear if you want to be able to stop or manouver. I would also get rid of that flyball governor.

[1967Brutus]

By the way, I absolutely like your idea!

It's something I would do...

[TomF]

Thanks for the comments, for power and reversing I have just bought a variable pitch prop which I hope will have a reverse pitch as well. Seems I got the last one! Also bought the blades 26mm long each and there are 4. The hub dia of 15mm makes the overall diameter 67mm just over 2.5 inches

[1967Brutus]

Wow! Where did you get THAT one? Is that the one from Microcosm?

All I have is this:

https://www.modelbouwforum.nl/attachments/20231030_124214-1-jpg.558956/

And although it is new in the sense of "unused" it probably is over 35 years old. Absolutely decent quality, and the plastic still is strong and flexible, but plastic nonetheless (in other words: only repairable by replacing parts) and no parts availlable since long.

It also is only 50 mm diameter with a hub of 21,5 mm

[TomF]

From here


Raboesch variable pitch Propeller Shaft- 395mm long (sussex-model-centre.co.uk)


But not available anymore, they have a longer one I think though


I was going to get the [size=0px]Microcosm one but this was half the price.[/size]
[/size]
[/size][size=0px]If you wait a day I will tell you if it can go into reverse.[/size]

[1967Brutus]

Wow... Raboesch... that normally is good stuff! I never knew they even had them.


For what it's worth, if I had to guestimate, I'd say if you keep that Holt replica at 1500~2000 RPM, that prop most likely is an excellent match.
The built on governor is rubbish, it won't be doing the job unless heavily oscillating RPM is acceptable.


That is however going to be a bit of a challenge, because I do not believe for one minute that the carb that Holt comes with, is any good, at all.
Like I said before, see if you can find someone to make you a heavier flywheel, and you're going to need a different carb.
Nothing is being made for this, but you can modify a twin needle carb of say, a ,25 glow engine.

I actually do have quite a bit of experience with modifying glow engine carburettors for use with gasoline. It's a tricky job but can be done, I've done about 20~25 of them for customers. If needed I can help you out.

I can totally see this working, but as I said before, it ain't gonna be easy and will take quite a bit of trial and error. Don't underestimate that.
When I modified my .30 fourstroke for gasoline and low RPM boat use, that basically was a project of 2 months every day all day (I am a seafarer, single, and as such in a position to spend that kind of time to a project) so be prepared for lots of evenings and weekends of tinkering.

But if you do, you'll have something most definitely very unique.

[1967Brutus]

From here


Raboesch variable pitch Propeller Shaft- 395mm long (sussex-model-centre.co.uk)


But not available anymore, they have a longer one I think though


I was going to get the [size=0px]Microcosm one but this was half the price.[/size]

[size=0px]If you wait a day I will tell you if it can go into reverse.[/size]

I have checked the bolded, and since I was considering a new and larger project in the future, I decided to bite the bullet and went ahead and bought it.
There was not much choice in sizes anymore, of course, but it turns out it's a hubof 25 mm, and a blade set of 40 mm, totalling a prop diameter of 105 mm, which should pretty much suit my purposes. Most likely going to be a large tugboat, powered by 10~15 cc low revving fourstroke.

Now finding a boat suitable for that propsize.

EDIT: Since that prop and blades most likely spent ages on a shelf at Sussex Model Centre, I figured it would be extremely unlikely that I would rob anyone from the opportunity to buy much needed spare blades, so I also bought the remaining set of 32 mm blades, just in case I can't find a boat suitable for a 105 mm prop.

When things start to take shape, I'll open a separate thread on it.

[1967Brutus]

I don't know where Topic Starter is at with his project, but here is my progress, so far only in the planning stage but the purchases have been done and this is what I've gotta make do with:

A few days ago I bit the bullet on a Cison OHV175,which is going to be adapted for slow speed operation, being coupled to the above mentioned 105 mm CPP, and the boat is going to be a 1950's era harbour tug of 110 cm x 32 and an estimated displacement of about 40 lbs.

That project is sooner or later going to be posted in the "working boat" section of this forum.

A link to the engine in question:

CISON L4-175 17.5cc Miniature OHV Four-cylinder Four-Stroke Engine Kits that Runs on Gas for RC Cars Ships - Stirlingkit

I opted for this engine for a number of reasons. Among those, the most conspicuous are:
-this engine has double pistonrings with oil control holes under the lower ring. I hope to achieve reasonable rates of oil consumption here.
-The water seal at the bottom of the liner is double, which is a feature that suggests the engine is purpose-designed to actually power something. contrary to being a desktop item built for aesthetics. 
-it has for its size the largest oil sump I could find,
-it has contrary to some other designs, adjustable valve clearance, which allows me to basically "tune" the valve timing for low speed operation,
-it comes as a "bare minimum" kit, so I do not pay for items I don't need such as radiator, governor or ignition system (I have better alternatives for those allready at hand)

There are things I don't like, which are going to be changed:
-I have little faith in the drive belts for cooling water and oil pump. They are going to be omitted alltogether because:
-the water pump is of poor design and will be replaced for an electric pump anyway. I need more flow in order to maintain even temperature distribution over the length of the cylinder block.
-The oil pump is as far as I can tell of sound design, but will be placed on a separate mount and also be electrically driven.
-This will also unload the crank a little bit, at idle the engine does not have to drive oil and water pump, making it easier to run these low RPMs, because 1500 RPM is actually frighteningly low for this type of engine.
-A proper oil filter arrangement will be needed, since the intention is for the engine to run longer periods (several hours at a time).

[1967Brutus]

Curious if there is any progress with OP's project?