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Author Topic: Running problems  (Read 2158 times)

pheonix

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Running problems
« on: March 26, 2011, 03:16:34 PM »

Wondering if any of you can help me out with a running problem (or lack of it!!) with my salvage project.

As a small project I bought a hull off flea-bay to utilize a 10cc engine and old 27Mhz system I had sitting on the back of a shelf.

The rebuild was fairly painless and everything works fine when I am running it on the bench (with cooling!) but as soon as I put it on the water it runs for about 30secs then stops. After bringing it back to the beach I notice the fuel line is empty.

I had the fuel tank pressurised by an outlet on the exhaust manifold but thought the gunk in the exhaust system might be blocking the take off which is mounted at the bottom of the manifold. I disconnected this and let the tank breath naturally and tried again but with the same results.

The only other obvious point is that I am running with the wrong prop - tried several that I inherited but they might be either two larger diameter or wrong pitch. The problem is I dont know what I should be running with - are at least one that I can use as a starting reference.

The hull is an old style "flattie" with an old Merco 10cc engine, direct drive/straight shaft with a 2BA thread at the end - it is used only for pleasure so not looking at getting every ounce of power out of it. Just want to go and have fun for a couple of hours.

Can anyone point me in the right direction please?? I have attached a couple of pictures as reference - one as received (yes I did replace the bent shaft  ;) ) and one end product.

Thanks for any help you can offer - be it prop size or other suggestions








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rshermanking

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Re: Running problems
« Reply #1 on: March 26, 2011, 04:35:42 PM »

hi Phoenix  just a phew things , is the fuel pick up tube long enough to reach the end of the tank and also fitted with a metal clunk , you also might want to try a small header tank fitted about the same hight as the carb, rather than take the pressure feed of the manifold were its high pressure take the feed from the end of the exhaust were its low pressure hope this helps .


                  rshermanking
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pheonix

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Re: Running problems
« Reply #2 on: March 27, 2011, 02:54:50 AM »

Thanks for the reply - the tank is a new Klunk type tank so all fittings were as supplied when bought. The pick up line reaches the lower edge of the tank and there is the brass weight/fitting at the end.

When I fill the tank I am careful not to fill over the breather pipe so even if its not pressuirsed it should be able to vent naturally.

When I start the boat the fuel runs easily to the carb and it runs ok on the bench, just under load it cuts out. I will investigate a header tank - any other thoughts??

Cheers
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martno1fan

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Re: Running problems
« Reply #3 on: March 27, 2011, 09:23:33 AM »

If its only cutting out under load then its a tuning issue,you cant tune carbs on benches it needs doing on the water  :-)).
Mart
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pheonix

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Re: Running problems
« Reply #4 on: March 27, 2011, 03:21:52 PM »

Thanks Mart

I have found that to start the engine I need 2.5 turns on the needle from the closed position - anything else always seems to struggle unless the engine is hot.

The boat is started in the craddle then transferred to the water where I adjust the needle with the carb about 1/4 - 1/3 open. When the revs reach the "sweet spot" i let the boat go - should I be tuneing it in with Throttle wide open???

I have just bought a new engine from Justengines for my latest project but its not quite ready for the water so i dont have anything to reference setting the old engine up against.

Am I setting it wrongly??

Cheers
Dave
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rshermanking

  • Guest
Re: Running problems
« Reply #5 on: March 27, 2011, 04:30:20 PM »

hi Phoenix due to the style of boat you may want to  change your launch technique, rather than putting the boat in the water then tuning and  letting go , start up as normal then if possible with help of someone else get them to throw the boat in at a shallow but flat angle . this should be done at about 3/4 - full throttle this way you will not load the engine up which could be why the engine cuts out .

    rshermanking
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David Shaw

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Re: Running problems
« Reply #6 on: March 27, 2011, 06:31:15 PM »

When was the tune pipe cleaned out. What you could be suffering from is to much back pressure because the pipe is blocked. Which usually shows up when the engine is under load, i.e. when in the water and not on the bench.
David Shaw
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pheonix

  • Guest
Re: Running problems
« Reply #7 on: March 27, 2011, 06:53:10 PM »

Many thanks for your replies gents.

Rshermanking - I have never launched like that so will give it a try.

David - This could be a very good point. The exhaust has been sitting as long as the engine (several years!!) - there is air passage though it but maybe not full flow and not something I had considered. I will take it out and give it a long soak in parafin to see if that helps.

Cheers
Dave
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Roadrunner

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Re: Running problems
« Reply #8 on: March 27, 2011, 07:28:12 PM »

hi Phoenix due to the style of boat you may want to  change your launch technique, rather than putting the boat in the water then tuning and  letting go , start up as normal then if possible with help of someone else get them to throw the boat in at a shallow but flat angle . this should be done at about 3/4 - full throttle this way you will not load the engine up which could be why the engine cuts out .

    rshermanking

Err no not with an engine driven boat... asking for a heap of trouble, loss of control if throttle sticks, launching wrong and it smashing into the floor bed (which can happen), and if it does cut out then you have a boat a drift you may not be able to retrieve quickly...

I think its down to tuning , opening the throttle and it stalls indicated to much fuel, chocking the engine and could hydraulic lock as worse case, you will need to lean out the fuel on the carb.

Best bet is on the water set its idle speed, then hold the boat (2 guys here preferable) and open the throttle a until you hear the loss in power then lean out the fuel needle (tighten it) open throttle again and see if the engine drops in power again, if it dose repeat the leaning out ( as a suggesting 1/4 turn at a time) one you have a rough setting thats not stalling the engine you can go back an tune it, lean it out a bit more if the engine is sill running cold but not to the point of starving it of fuel and 'riching' it up if the engine is running hot.

Its a matter of experience when it come to tuning engine's, took me nearly 10 years to master the skills of decent tuning, but that includes 3 needle carb's as well.

Just a shame engines are banned locally here nothing i would love more then the stick a engine in a boat instead of messing around with electrics  >:-o
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omra85

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Re: Running problems
« Reply #9 on: March 27, 2011, 10:54:29 PM »

Pheonix, a couple of tips that may help you.
Check if your tuned pipe is blocked by blowing through it (you might want to wrap a tissue round the end first - unless you like the taste of burnt castor)
You should be able to blow fairly easily through it.  If it is steel, then you can use drain cleaner in it for a few days, then rinse thoroughly. Don't try this with aluminium though!!  It will dissolve it.  For ally pipes, you can use the splayed out end of a short flexi drive in a SLOW electric drill.  Put a tube over the flexi to stop whipping then hold the tube and feed the assembly through the pipe as a sort of rotary brush.

Tuning should not be done either on the bank or held in the water.  The loading when running is far less than when static in water, and far more than running in air.  Also the engine is getting little, if any, water through it so can easily overheat.
The best way is to get it running steadily but rich at 1/3 to 1/2 throttle, then launch the boat (having first checked the throttle and rudder are functioning.  Drive round in a circle without touching the throttle then, when the boat is passing you slowly open the throttle (this way, if the engine cuts, it will be close to you for retrieval).  I suggest you invest in an old fishing rod, some strong line and a tennis ball.  Fasten the ball to the line then, to recover the boat, cast the ball over the top of the boat and haul it in :-)

If you absolutely MUST try tuning when holding the boat in the water, push the nose of the boat down so that the prop almost clears the water.  This will reduce the load on the prop so you will get a slightly more accurate setting - but this should not be done for long even if you have some cooling going through the head.

You can make 1/4 turn adjustments and repeat the process until you are happy.  It's a pity you haven't a local club with an IC guy as it takes longer to describe the process, than it does to do it.
 {-) {-)  
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ids987

  • Guest
Re: Running problems
« Reply #10 on: March 28, 2011, 02:14:53 PM »

Danny's on the money as usual - you can't gauge the needle setting either on the bench, or static in the water. I normally start with an off load setting which is on the rich side - revs build gradually when you open the needle wide open, and won't reach ultimate top revs without load. You need to be careful not to do it for too long, and not to overrev as well. I don't run pressure feed, and that may change things slightly. If it's a Merco carb, from what I remember, the thread on the needle is coarse, so I would think 2.5 turns open with pressure is likely to be very rich.
The pipe is definitely Ali, so caustic soda is out of the question. Pretty sure it's an ED Power Pipe. Probably an ED No.3. If you unscrew the nut at the end of the silencer can, the silencer can should come off. The baffle pipe goes straight through the silencer (welded into the rear end of the convergent cone, threaded end to the outside world, so if it is clogged, you can easily clean the holes out manually.......
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ids987

  • Guest
Re: Running problems
« Reply #11 on: March 28, 2011, 02:16:28 PM »

Danny's on the money as usual - you can't gauge the needle setting either on the bench, or static in the water. I normally start with an off load setting which is on the rich side - revs build gradually when you open the needle wide open, and won't reach ultimate top revs without load - then fine tune as Danny says. You need to be careful not to do it for too long, and not to overrev as well. I don't run pressure feed, and that may change things slightly. If it's a Merco carb, from what I remember, the thread on the needle is coarse, so I would think 2.5 turns open with pressure is likely to be very rich.
Any idea what props you have tried so far. You won't get a good setting unless the prop is right - or at least close.
The pipe is definitely Ali, so caustic soda is out of the question. Pretty sure it's an ED Power Pipe. Probably an ED No.3. If you unscrew the nut at the end of the silencer can, the silencer can should come off. The baffle pipe goes straight through the silencer (welded into the rear end of the convergent cone, threaded end to the outside world, so if it is clogged, you can easily clean the holes out manually.......
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pheonix

  • Guest
Re: Running problems
« Reply #12 on: March 28, 2011, 06:31:46 PM »

Pheonix, a couple of tips that may help you.
Check if your tuned pipe is blocked by blowing through it (you might want to wrap a tissue round the end first - unless you like the taste of burnt castor)
You should be able to blow fairly easily through it.  If it is steel, then you can use drain cleaner in it for a few days, then rinse thoroughly. Don't try this with aluminium though!!  It will dissolve it.  For ally pipes, you can use the splayed out end of a short flexi drive in a SLOW electric drill.  Put a tube over the flexi to stop whipping then hold the tube and feed the assembly through the pipe as a sort of rotary brush.

Tuning should not be done either on the bank or held in the water.  The loading when running is far less than when static in water, and far more than running in air.  Also the engine is getting little, if any, water through it so can easily overheat.
The best way is to get it running steadily but rich at 1/3 to 1/2 throttle, then launch the boat (having first checked the throttle and rudder are functioning.  Drive round in a circle without touching the throttle then, when the boat is passing you slowly open the throttle (this way, if the engine cuts, it will be close to you for retrieval).  I suggest you invest in an old fishing rod, some strong line and a tennis ball.  Fasten the ball to the line then, to recover the boat, cast the ball over the top of the boat and haul it in :-)

If you absolutely MUST try tuning when holding the boat in the water, push the nose of the boat down so that the prop almost clears the water.  This will reduce the load on the prop so you will get a slightly more accurate setting - but this should not be done for long even if you have some cooling going through the head.

You can make 1/4 turn adjustments and repeat the process until you are happy.  It's a pity you haven't a local club with an IC guy as it takes longer to describe the process, than it does to do it.
 {-) {-)  

Thanks Danny, your advice is much appreciated.

I am currently working offshore but due home next week, if the ice has finally melted of my local Loch then I will go and experiment  %) It seems like the pipe is the best (and easiest) place to start so I will strip it out and have a look at it. I know there is some air passage through it but whether its the full flow I dont know. The engine was extremely gunged up when I dusted it off after all the years in storeage so there is a very strong probablity the pipe is no better - the fact it could be gunged up never crossed my mind, was busy stripping and cleaning everything else.....................

I went one better than the fishing rod - ended up buying a cheap blow up boat so I can go rescue the small ones when they stop in th emiddle of the Loch, problem is I am getting lots of rowing experience   >>:-(

Cheers
Dave

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pheonix

  • Guest
Re: Running problems
« Reply #13 on: March 28, 2011, 06:42:41 PM »

Danny's on the money as usual - you can't gauge the needle setting either on the bench, or static in the water. I normally start with an off load setting which is on the rich side - revs build gradually when you open the needle wide open, and won't reach ultimate top revs without load. You need to be careful not to do it for too long, and not to overrev as well. I don't run pressure feed, and that may change things slightly. If it's a Merco carb, from what I remember, the thread on the needle is coarse, so I would think 2.5 turns open with pressure is likely to be very rich.
The pipe is definitely Ali, so caustic soda is out of the question. Pretty sure it's an ED Power Pipe. Probably an ED No.3. If you unscrew the nut at the end of the silencer can, the silencer can should come off. The baffle pipe goes straight through the silencer (welded into the rear end of the convergent cone, threaded end to the outside world, so if it is clogged, you can easily clean the holes out manually.......

Thanks for your reply - you are correct, the needle has a very course thread compared to the new engine ASP engine I bought for my other project. In fact I was tossing up about replacing the carb with something a little more modern.

The pipe is Ali and I bought it over 20years ago when I was at college from my local RC shop. It was well used in the early days but then its sat collecting dust so as I said in reply to Danny's post I will start there first. Didnt realise it could be dismantled but I will certainly have a close look when I get back home and see if I can un-screw the top plate.

Once I get that sorted i will turn my attention to the tuning - would be realy nice to have a decent run out of it again. Not expect to break any speed records, just have a couple of hours fun on the Loch side when I feel like it.

Cheers
Dave
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