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Honda 20hp loose power

jasoncalleja

Regular Contributor
Hi all i have a small problem i don’t know if it’s a common one my Honda bf20 (20hp). After i have been running for some time and i stop for a few seconds i can plane back in seconds but if i stop for a few minutes i can’t get on plain. It is like if the motor is tired or looses power it is propped perfectly. Is this normal or it is something wrong ? Thanks
 
The motor is all the time started i did not turn it off but put on neutral. Could it be because here in Malta we don’t have a good quality fuel? May be i need to add something to the fuel ? and if yes what shall i add ? thanks
 
I do know if low quality fuel would do this.

You did not say if you ever do get up on plane. If so, how long will it take to plane after this happens?

When this happens, try to squeeze the fuel bulb until it is hard to see if it helps. You may be having a fuel delivery problem.

Mike
 
Hi mike and thanks for your reply. This is what is happening i put my dinghy in sea and start the motor i give it chance to reduce revs than i drive it and in 5sec it is on plane and go for a ride and its ok but when i stop and go to neutral for some seconds i can plane again in seconds. if i stop to answer a phone call for a few minutes (engine still started) then i try to go on plain again and it gives me hurt time i will have to go on the front so it can plain. It is like that the motor looses power when it is warm. I have tried squeeze the fuel bulb but it is full of fuel. That is why i thought it may be fuel problem too. What do you think? This thing had never happened before. Do you think i have to check valve settings the out board has about 25hrs. Could it be that when it is warm lose some compression from valves. Thanks Jason
 
I guess it is possible that the valve clearances need adjusting. But I really do not know.

It will have to think about this one. I do not have any immediate answers to the problem.

Maybe Jimmy has some thoughts.

Mike
 
Man! If you have a 20 hp on your dinghy, I want to see your yacht!

It sounds like it could be that the engine is idleing too slowly and "loading" up possibly fouling the plugs. Try bumping up the idle set screw 1/8 to 1/4 turn and see if that doesn't help.

If you are running poor quality fuel, then yes, you may want to add a fuel modifier like Sea Foam or Lucas Fuel Injector Cleaner along with fresh plugs to help keep carbon from forming in the combustion chamber.
 
Hi my friends yes it is running a little bit slow on idling. Do you suggest replace plugs? And bty i only own the 12ft rigid hull dinghy i have no yacht i don’t afford it. If one day i can buy something ells i will buy an extra large rib with some 225 Honda!!!!. That’s my dream. Thanks jason
 
I would try increasing the idle speed first then run the boat as you normally would. For now, you could just remove and inspect the plugs. They should be sort of brown at the end. Not black and not light grey or white.
 
I have increased idle speed and checked plugs they where black and replaced them tomorrow i will try it on the sea and will let you know how it will be. Thanks jason
 
Hi all i have run the out board and i have not noticed any improvement after the replacement of plugs and adjusted the idle speed. I have noticed that after i get it on plane it can revs to 6000rpm but the motor is like if it is lack of power if i find some waves il get of plane like if there is something holding you from the back. One last think if water had entered from the idle exhaust port could it be that it causes this lack of power and if yes what kind of damage could be? Thanks Jason
 
That phrase "feels like something is holding you from the back" while it is turning 6k rpm makes my mind go to the prop. When the hub first starts to fail, it will drive the boat but will slip some as it heats up. Have you hit anything with the prop? Have you checked it lately for fishing line and thrust washer condition? Do you have a spare you can try?

I hope someone else can give you some more ideas.

Other than that, I suppose you could have a fuel quality issue. You said the plugs you replaced were black and that usually indicates a rich mixture or too cold of a heat range but poor fuel volatility would cause incomplete combustion and that could be carboning up the chamber. Is there a source where you might pay a bit more and possibly try some "premium" fuel since you stated before that the fuel in Malta is questionable?
 
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I will check the prop and yes i have another one i will try it i will re check the plugs again to see if they are black again. About the fuel i can’t try different one as here they only bring one type of unleaded fuel. This type of fuel is hi evaporated one i don’t know if it is good or no to be hi evaporated ?
 
Not sure what hi evaporated gas is. It is not something I've heard before. It may be a different way of saying it is oxygenated but that is just a guess.
 
Nothing that I can send. All my pictures and instructions are in a copy protected format. I recommend that you purchase a repair manual from Helminc.com. It is full of valuable information, if you are going to do your own maintenance. Not sure if they ship to Malta

Mike
 
Hi all . First of all i installed a set of hydrofoils and these helped to plain easily all the time. Last Tuesday i tried the motor and drive it in full open throttle but the motor wouldn’t go to 6000rpm as normally it dose i checked the propeller and its ok i checked the cable that it is going gas down and it was ok too all i have noticed that the fuel bulb is not hard all the time although it doesn’t helped it and i don’t know if this is normal while it is running to not be hard. What is your opinion after all this. Thanks for all your information and help Jason
 
What is the bronze adjuster in the carburettor used for ? fuel mix or air mixture? I cleaned the carburettor as i wanted to check if there was any fuel gum but i have not found nothing in i have checked fuel pump and filters pipe line and all the fuel system and seems to be ok. Normally when i have finish using the motor i leave it running out of fuel. Is it good to do this or no? I do this every use. Thanks
 
Not sure what a "bronze adjuster" is. I'm only familiar with the BFD models.Those carbs only have two adjustments: idle fuel circuit and a linkage screw for setting final idle rpm. The idle fuel screws on them have a limiter cap on it so that it cannot be tampered with. You actually have to break it to alter the adjustment from the factory setting. Not sure about yours although I suspect that it is similar except it may not have the limiter cap. I will caution you that cleaning these carbs can be a bit more involved than most people think and if you do disassemble one, you should have, at the very least, replacement "O" rings and seals for reassembly. There is one oring that is critical to the proper operation of the carb and when it is disturbed, it should not be reused.

Running the engine "dry" is a fairly accepted practice but if you live in a hot climate, I don't recommend doing that. Burning a lean mixture creates high combustion chamber temperatures and could lead to the fuel "detonating". This usually results in pre-ignition of the fuel and causes the engine to backfire through the intake which causes valve and carburetor damage. Running the engine until it stalls also does not completely accomplish what you are trying to achieve anyway, which is to drain the fuel from the carburetor bowl. Honda has provided, and now recommends that you use, a drain screw in the float bowl. It is attached to a rubber hose and drains the float chamber COMPLETELY out the hose and away from the engine with a port located just next to the water pee port. Only this method will ensure that any and all sediments in the bottom of the fuel chamber are expelled. Again, your engine may not have this, I don't know.

It is admirable that you try and drain the carb after each run as that does help keep trouble away.
 
The carburettor on my 2008 Honda bf 20 has only 1 adjuster it is of bronze and it is tapered as a needle and yes it has an o ring and it is a flat screw head it is an adjuster for sure and it has the drain screw too as you said .thanks for your reply i will try adjusting it in the sea and check if it will help the problem. Thanks again Jason
 
Yes, I haven't worked on anything later than an '05 so I guess the limiter cap has been dropped...thankfully. That is where they put it, on the idle fuel screw (#4). I'm not sure if that circuit will be the answer to your problem though. It is always a good practice to pull out the adjustment screw and spray carb clean through the passage and then replace the seal. You should open the throttle plate and backflush the passage through the hole in the venturi.

However, I predict that your problem will either be in the accelerator pump circuit (#14 in the diagram) AND/OR the intermediate circuit jet (#18 in the diagram). with the intermediate jet being clogged or damaged or the "O" ring not sealing. That little oring sealing is critical for proper fuel delivery. If you disturb it, replace it using great care not to damage it upon installation.

I have pretty much stopped trying to clean the intermediate jet and just replace it as the internal passage can get a small piece of hard deposit in it and that can be almost impossible to remove completely. It can also get a hairline crack in it and that can be hard to see. If you decide to clean yours, use a magnifying glass for inspection.

The accelerator pump circuit is also pretty critical for this carb to deliver fuel properly. I always backflush this circuit using carb spray and spraying into the small orifice in the brass (or bronze) tube that juts out into the front of the carbureator throat. This requires that you use the plastic straw that comes with the spray can and open the throttle plate. Go through the back side of the carb throat to reach it. I backflush all passages this way. Idle, intermediate, main and accelerator.

Replace the protective boot (#12 cap in the diagram) on the accelerator pump pushrod. If that boot tears, it will allow dirt and moisture into the carb as well as causing a fuel leak that could be a fire hazard.

If you find any scoring of the accelerator piston sleeve or if the check ball at the bottom of the pump circuit is loose or falling out, replace the float chamber. Just consider it a wear item and don't try to fix it. Even with a new chamber, I thoroughly flush all the passages in the chamber. I've gotten new ones out of the package with debris in the vacuum break passage.

I hope that you understand that I am trying to emphasize how absolutely important it is to clean out all of these passages in the main body and in the float bowl/chamber and then to get the new seals in place without damage.

It comes to about $80 for all these parts but you get some really good peace of mind value by replacing them. Sorry about the long post. Good luck.
 
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You don’t have to be sorry for nothing it is a pleasure to me read all this helpful information i don’t have enough worlds to thank you. Thanks again Jason
 
If you can turn your idle mixture screw, it should be set 2 1/8 turns out from it being fully seated.

Just as Jimmy says, if you have bad fuel, one of the most likely problems will be the bowl (#5) and/or the accelerator pump (#14). They have to be ordered separately. I almost always change #18 also, since if it has any blockage, it is impossible to be sure that you get it completely clean. There are small ledges where the tube changes size and carb gunk (a technical term) can get caught in that area then break loose later and clog the small tube. That will screw up idle and transition.

Mike
 
The idle mixture screw is set 4 1/8 turns out from it being fully seated.
it is the adjustment from the factory as i have never touched it. do you think i have to set it as you said 2 1/8 turns? Thanks jason
 
The 2 1/8 turns out is the factory specification and it shouldn't need to be out or in too much from that. If you purchased the engine new, it was either set incorrectly initially, tampered with prior to your purchase or, more likely, the spring has become weak and has allowed the adjustment to back off due to vibration. I would recommend that you replace the needle valve, spring and seal as an assembly and set it to 2 1/8 turns out.
 
The motor is about 12 months and i have opened it from the sealed box and it has about 30 hrs do i have to replace it or gust set it as it has few hrs on it
 
Well then, just set it at 2 1/8 and see what happens. But, if it slowly changes and backs out again, replace the assembly.
 
Hi my friends thanks for all your help tried the outboard and it has gained power again so i think it was fuel problem that was causing it. And for the adjuster it was set correctly i was counting the turns wrong .Thanks a lot Jason
 
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