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Author Topic: 28cc WEEDWACKER MODIFIED TO WATERCOOLED MARINE ENGINE  (Read 17100 times)

Patternmaker

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28cc WEEDWACKER MODIFIED TO WATERCOOLED MARINE ENGINE
« on: March 02, 2009, 06:49:58 PM »

Dismantled and cylinder machined for water jacket,
Water jacket machined from 70mm aluminium bar
Flywheel housing machined for rear engine mount and flexishaft coupling
Clutch and bearing discarded, bearing housing retained for rear engine mount
Front and rear engine mounts made from 3mm aluminium to fit 5inch rails
Custom made header from stainless steel
Custom made aluminium water cooled flange manifold

Total weight with tune pipe     2.32kg

Original weight with                 3.20kg
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Patternmaker

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Re: 28cc WEEDWACKER MODIFIED TO WATERCOOLED MARINE ENGINE
« Reply #1 on: March 02, 2009, 07:04:15 PM »

More Pictures
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john54

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Re: 28cc WEEDWACKER MODIFIED TO WATERCOOLED MARINE ENGINE
« Reply #2 on: March 02, 2009, 07:50:12 PM »

Price ? & power(ish)
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Bill D203

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Re: 28cc WEEDWACKER MODIFIED TO WATERCOOLED MARINE ENGINE
« Reply #3 on: March 02, 2009, 08:48:23 PM »

Hello.
Looks like a good job well done. Couple of points. What are you going to put it in?
If you want to Run it in OMRA races there are set sound limits. Your pipe looks as if it has no baffles to keep the noise down. The Cylinder head looks like it only has 2 head bolts. If so when you run the engine make sure you pull them down again after 1/2 hour ruining. I tell you this as it happened to me and did the jug in.
All that said Well done. Where did you get the engine from and How much? A Sick/Zenoha will set you back between £ 175/ £ 195 at todays prices.
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Patternmaker

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Re: 28cc WEEDWACKER MODIFIED TO WATERCOOLED MARINE ENGINE
« Reply #4 on: March 02, 2009, 09:27:02 PM »

Hi Bill, I might put it in 45" deep vee, because the engine has a larger flywheel than a zen its not really suited for a cat, I got the engine from ebay new for £22.95 I actually bought 2. I am am making a copper head gasket.
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Bill D203

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Re: 28cc WEEDWACKER MODIFIED TO WATERCOOLED MARINE ENGINE
« Reply #5 on: March 02, 2009, 10:03:23 PM »

Hi Bill, I might put it in 45" deep vee, because the engine has a larger flywheel than a zen its not really suited for a cat, I got the engine from ebay new for £22.95 I actually bought 2. I am am making a copper head gasket.
Hello
Yes I did see them on e bay. Look like you have done a good jon of converting the engine. I hope you enjoy the boat when you get it running. Good luck.
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andyn

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Re: 28cc WEEDWACKER MODIFIED TO WATERCOOLED MARINE ENGINE
« Reply #6 on: March 02, 2009, 10:05:20 PM »

You got the time to batch produce them? You could sell them for £80 ish each and make a handsome profit O0
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glennb2006

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Re: 28cc WEEDWACKER MODIFIED TO WATERCOOLED MARINE ENGINE
« Reply #7 on: March 03, 2009, 01:23:31 PM »

Hi Bill, I might put it in 45" deep vee, because the engine has a larger flywheel than a zen its not really suited for a cat, I got the engine from ebay new for £22.95 I actually bought 2. I am am making a copper head gasket.

Really nice looking conversion job, are you going to do some porting work to alter the engine timing and wake the motor up a bit? What type of motor is it?

Glenn
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Patternmaker

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Re: 28cc WEEDWACKER MODIFIED TO WATERCOOLED MARINE ENGINE
« Reply #8 on: March 03, 2009, 02:35:54 PM »

Glenn, The ports have been modified and polished, I will wait and see what the power output is like before I do anything else. I will run the standard one and check RPM angainst the modified one.
Apart from a Sovereign label in the strimmer, which I have never heard of I think the engine is Chinese origin, very well made with the same diameter crankshaft and bearings as a Zenoah but with a larger flywheel and runs very well on idle.
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Patternmaker

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Re: 28cc WEEDWACKER MODIFIED TO WATERCOOLED MARINE ENGINE
« Reply #9 on: March 06, 2009, 06:03:07 PM »

John, I have just seen your post from June last year (anyone know anything about
These hulls) I recently bought one of these hulls from ebay from a private seller it had obviously been laying about for a few months and the deck and cowl were scratched so I have had to restore by painting.
Quite a nice hull very similar to PMC deep V 2”shorter but with a little more freeboard, not the best quality moulding I have put an extra layer of cloth in the hull and round the stringers to stiffen it up. The hull originates from china and is called Blade.
I am going to fit the 28cc weedwacker engine running a 70mm 110mm 3 bladed prop
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martno1fan

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Re: 28cc WEEDWACKER MODIFIED TO WATERCOOLED MARINE ENGINE
« Reply #10 on: March 24, 2009, 05:54:41 PM »

Hi mate that motor is the same one i had in my old vee it actually ran flawlessly as an air cooled motor.I was told by a guy they are made by zenoah which would account for the good quallity and the bearings etc.I installed a walbro 167 carb and she ran very well,def need to ditch the stock carb as its junk.With some porting work id say she would be a very good little motor.Best prop hands down for this low revving motor was a big prather 280 2 blade prop.
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Patternmaker

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Re: 28cc WEEDWACKER MODIFIED TO WATERCOOLED MARINE ENGINE
« Reply #11 on: March 24, 2009, 08:30:58 PM »

I have run both engines the modified one recorded 11,217rpm at full throttle on the tacho an increase of nearly 4,000rpm on the standard engine with the standard carb, which do not consider low reeving and will stay with my prop choice.
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martno1fan

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Re: 28cc WEEDWACKER MODIFIED TO WATERCOOLED MARINE ENGINE
« Reply #12 on: March 24, 2009, 09:07:03 PM »

The stock motor is low revving that was my point,the stock carb doesn't help either which is why i used a walbro 167.That said 11,000 rpm isn't high revving either the stock zenoah puts out almost 14,000 rpm with a pipe.For a stock zen you'd be looking at the prop your using or similar,i ran a 6717/3 on a stock zenoah but for anything lower rpm you would in my opinion be better with a larger prop.The stock sovereign motor with the 167 carb was putting out around 8,500 rpm ,a mate of mine had several of them and fastest speed he measured on the gps was  34 mph and that was with the big prop anda  pipe with 90% header.Be interesting to see what speed  you get with the mods you have done but i still think the big prop will work best,no harm in trying either.In fact no point just trying one prop on any setup if you want to find the best prop for it.Also your header will be way too long to achieve a good tuned length,you would be best with a 90% header rather than the wtc if your looking for higher rpm.I admire your workmanship though,just not sure its worth the time and effort for this motor.Its a great runner as stock for a play boat not sure how it will be reliability wise with mods done to it but i wish you luck.Its def a better motor than the ones seen on ebay in the cheap china boats.In fact if you get it running well and plan on doing any more id take several off your hands.
Mart
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glennb2006

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Re: 28cc WEEDWACKER MODIFIED TO WATERCOOLED MARINE ENGINE
« Reply #13 on: March 25, 2009, 02:09:16 AM »

Also your header will be way too long to achieve a good tuned length,you would be best with a 90% header rather than the wtc if your looking for higher rpm.
Mart

Mart,

what would you recommend for a tuned length on the engine that pattermaker has modified?

I'm thinking that with the sort of timing the motor most likely has at stock, and the fact that it is going to be running lower RPM then it might well be possible to achieve the correct tuned length from that header. What do you reckon?

Patternmaker - have you measured the exhaust timing duration yet?

Glenn
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martno1fan

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Re: 28cc WEEDWACKER MODIFIED TO WATERCOOLED MARINE ENGINE
« Reply #14 on: March 25, 2009, 08:25:36 AM »

Well if you look at the header its actually longer than your usual wtc header so my thinking is its too long,granted his tuned length will need to be longer than on a zenoah.I supose without testing it he wont know,im just saying in my opinion it will be too long.Just trying to give him my opinion based on my experience with this engine,even though its slightly modified i still say the prop needs to be bigger too.My old mate Rick actually modified one of these and it was putting out arround 15,000 rpm on a dyno but he never actually got it on the water to do any testing.
Mart
Heres a pic of mine with a tuned pipe,even in this pic the pipe was set too long.
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martno1fan

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Re: 28cc WEEDWACKER MODIFIED TO WATERCOOLED MARINE ENGINE
« Reply #15 on: March 25, 2009, 09:15:28 AM »

Just want to say to patternmaker in no way am i critisizing what your doing in fact i like what you have done so far.Just giving you another point of view,if you do intend doing any more i would def be interested .Another possibility to try is one of the ready welded up pipes with wtc header,theyre probably about the correct length for that kind of motor.They tend to work better than the seperate wtc header and pipes as theyre a tad shorter,at least the ones i had were.
Mart
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Patternmaker

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Re: 28cc WEEDWACKER MODIFIED TO WATERCOOLED MARINE ENGINE
« Reply #16 on: March 25, 2009, 11:14:10 AM »

The reason I water-cooled the head is because so much of the cowling had to be removed air cooling would be not be sufficient, I have left the fins on the flywheel to help cool the crankcase, some of these engine mods the fins are machined of to save drag. I have managed to get a new very cheap carb not a walbro but almost identical with a 13.49 venture.
Because of the type of hull I have had to use a wtc tune pipe therefore I have no choice with the header, yes a compromise but it remains to be seen what performance I will get.
A stock zen 260 PUM produces max power of 2.16kw at 12000rpm and max torque of 1.94 at 9500 rpm, with cylinder displacement of 25.4. The 14000 rpm is obviously not under load
The weedworker has a displacement of 28.2, according to my calculations I will get a torque figure of over 2.00 at 9500rpm
 
I have been modifying petrol engines for nearly 30 years the first was a 22cc McCullock chainsaw engine which held the spark ignition (as it was known then) record in 1984 of 32.4 mph in a boat I designed and built which I still have
and won many offshore races which incidentally weighs nearly 14 kgs. The problem was they were fitted with points and condenser and not very reliable when they got wet, also the flywheels tended to burst at high RPM. With horrendous results.

My friend Naviga world champion 1988, 1994 & 1998 Dave Marles who has been designing and racing boats for many years suggested the prop size all due respect but I would think he has more experience than yourself and I value his expertises.

As for is it worth the trouble, I do not have a bottomless pit, if I can get the engines performance to equal the stock zen for less than 30 quid, I consider it to be well worth the trouble.
Everyone is entitled to their opinion and suggestions are always welcomed

Incidentally the Mercury Cat I built has been officially timed by his club at
64.3 mph with a stock zen a 257 carb.

Glenn,
the exhaust duration is 164 degrees

When we look today, we see incredible speed records and high standards of competition. We've learned that speed means serious attention to details and that our models require the best materials and demand our very best driving skills. Engines and radios provide nearly flawless performances, and the difference between winning and not boils down to each individual's performance, preparedness and motivation There are two things that I am absolutely certain will remain the same; speed records will continue to be set and broken, and the skills and motivation of the modeller will be the deciding factor as we continue to raise the bar to new heights. I hope we can continue to have fun along the way.
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martno1fan

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Re: 28cc WEEDWACKER MODIFIED TO WATERCOOLED MARINE ENGINE
« Reply #17 on: March 25, 2009, 11:50:21 AM »

Never had any problems with running mine air cooled but it wasnt modded in fact its still going 3 yrs later,the guy who has it still runs it with no problems.Of course i ran mine in an open boat but as it wasnt a race boat that was fine for me at the time.As for Daves recomendation on prop all i can say having run that motor for over a year and trying all manner of props as i say the bigger props worked better. Dave himself recomended to me  that the x482 is the prop of choice for a weedwacker motor or he did when i was building mine,even the guys running the homies that are suposed to rev higher than these go for the bigger props.I didnt like the price of the octura prop so went for the prather which was cheaper for me at the time.Can i ask what tests have you done to test your motor under load?.As for the mercury cat doing 64 mph with a  stock zenoah id like to see that i really would is there any video of it?.Ive seen one up close and personal with a zen 7 and i doubt it was much if any faster than 64 mph at the time.
Mart
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glennb2006

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Re: 28cc WEEDWACKER MODIFIED TO WATERCOOLED MARINE ENGINE
« Reply #18 on: March 25, 2009, 01:57:49 PM »



When we look today, we see incredible speed records and high standards of competition. We've learned that speed means serious attention to details and that our models require the best materials and demand our very best driving skills. Engines and radios provide nearly flawless performances, and the difference between winning and not boils down to each individual's performance, preparedness and motivation There are two things that I am absolutely certain will remain the same; speed records will continue to be set and broken, and the skills and motivation of the modeller will be the deciding factor as we continue to raise the bar to new heights. I hope we can continue to have fun along the way.


A very true statement, so many people take for granted what we have available very easily (cheaply) in the current times we live in.

Not that long ago, carbon fibre and kevlar technology was reserved almost exclusively the aerospace and military sector - now it is not uncommon in model boats as well as ever where else.

I look forward to seeing how you get on with the motor - I'm sure Dave will give you some timing figures to work towards and see where you end up. Guess as always it's a case of how far are you going to push it - just a bit more might be the end of it. (Ask me how I know!!)


To quote yourslef - have fun.

Glenn
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Patternmaker

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Re: 28cc WEEDWACKER MODIFIED TO WATERCOOLED MARINE ENGINE
« Reply #19 on: March 25, 2009, 03:18:08 PM »

Never had any problems with running mine air cooled but it wasnt modded in fact its still going 3 yrs later,the guy who has it still runs it with no problems.Of course i ran mine in an open boat but as it wasnt a race boat that was fine for me at the time.As for Daves recomendation on prop all i can say having run that motor for over a year and trying all manner of props as i say the bigger props worked better. Dave himself recomended to me  that the x482 is the prop of choice for a weedwacker motor or he did when i was building mine,even the guys running the homies that are suposed to rev higher than these go for the bigger props.I didnt like the price of the octura prop so went for the prather which was cheaper for me at the time.Can i ask what tests have you done to test your motor under load?.As for the mercury cat doing 64 mph with a  stock zenoah id like to see that i really would is there any video of it?.Ive seen one up close and personal with a zen 7 and i doubt it was much if any faster than 64 mph at the time.
Mart

No I have not done any load tests on the engine yet, I would not even consider asking the owner if there is any video for proof,  I have no reason to doubt his
word or his club officials
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martno1fan

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Re: 28cc WEEDWACKER MODIFIED TO WATERCOOLED MARINE ENGINE
« Reply #20 on: March 25, 2009, 04:09:07 PM »

Look forward to seeing how she works out for you ,as regards the video im genuineley interested in seeing it if there is one as ive never heard of any cat doing that sort of speed with a  stock zenoah so maybe i could learn something.
Mart
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Patternmaker

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Re: 28cc WEEDWACKER MODIFIED TO WATERCOOLED MARINE ENGINE
« Reply #21 on: March 25, 2009, 04:13:28 PM »

My 22cc McCullock Spark ignition Class boat from the early eighties
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andyn

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Re: 28cc WEEDWACKER MODIFIED TO WATERCOOLED MARINE ENGINE
« Reply #22 on: March 25, 2009, 04:13:42 PM »

Are we sure thats MPH? the mercury looks quite blockish and not incredibly streamlined, it is a big bore crab but on a stock zen??
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Patternmaker

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Re: 28cc WEEDWACKER MODIFIED TO WATERCOOLED MARINE ENGINE
« Reply #23 on: March 25, 2009, 04:28:51 PM »

You might be interested in the following links               
http://www.youtube.chttp://www.youtube.com/watch?v=yIV8ByYhkwYom/watch?v=PwIoboKT8lQe
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martno1fan

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Re: 28cc WEEDWACKER MODIFIED TO WATERCOOLED MARINE ENGINE
« Reply #24 on: March 25, 2009, 04:32:13 PM »

Mick the links not working for me and im interested  ok2
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