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Low/Poor power performance?

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paulpowell3540

New member
I have a Honds 25hp BF25 (2003) on an aluminium 4.2mtr Quintrex Estuary Angler.
WOT only returns a maximum speed of 14 to 15 knots with two adults on board - is this normal or is there a problem with the motor?
I have used fresh fuel and added F10 carb cleaner - no improvement. The suggested power unit for this boat is 30hp so I know its a little underpowered but would have though it had more guts than this??
Any advice welcome!

[email protected]
 
Ok , you really need to do a compression test. Then check to see if it has spark on all 3 cylinders.----------It may be as simple as a bad spark plug as well.------------How long have you owned the motor ?---Do you run fuel out of carburetors when motor is not in use?------------Any history on maintenance??------------Do you have the correct prop?
 
racerone said:
Ok , you really need to do a compression test. Then check to see if it has spark on all 3 cylinders.----------It may be as simple as a bad spark plug as well.------------How long have you owned the motor ?---Do you run fuel out of carburetors when motor is not in use?------------Any history on maintenance??------------Do you have the correct prop?
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I have had it 4 years (it is about 9 years old) Compression was tested at service - all three cylinders good - It is serviced every 6 months and has new plugs in it. I have tried all positions on the adjusting pin for the pitch - no improvement
I have seen a lot of other boats the same size with 30 or 40HP - never seen a 25 on one yet so I am wondering if its underpowered??
The previous owners were in their mid 70's and bought the rig new just to potter up the river so they only out a 25HP on it>
 
There is something wrong ! ---the boat should do very well with a 25 HP.-----------------I will ask once more, do you run fuel out of the carburetors when done boating ?--------Have you verified spark on all 3 cylinders ?-------Is this something that happenened suddenly ?? ------Is the boat bottom fouled , left in the water all the time ??
 
racerone said:
There is something wrong ! ---the boat should do very well with a 25 HP.-----------------I will ask once more, do you run fuel out of the carburetors when done boating ?--------Have you verified spark on all 3 cylinders ?-------Is this something that happenened suddenly ?? ------Is the boat bottom fouled , left in the water all the time ??
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Thanks for you help - I don't run the fuel out - only at the end of summer when its going into winter store under the carport, so it would have fuel sitting in the carbs sometimes for several months, its performed like this since Ive had it but as its my first boat I assumed this was it! - I don't use it all that much except of late Ive had it on the water a bit more and noticed other similar sized boats with a 25HP doing much more than mine so I started to ask people on the water and they tell me one of two things (1) the carbs need cleaning or (2) you need a bigger engine - Honda 4 strokes are not as good as 2 stroke!! - its a trailer boat so the alluminium hull is fine and clear - Im pretty sure its sparking on all three (new plugs last service) as it runs quiet and smooth - The gear engage/throttle goes from vertical - forward 45 degrees - It accelerates up to a bit over halfway but when I push it down the remainder forward - nothing happens in revs increase or speed.
I am happy to spend money on a carb clean and tune/balance as long as it will perform but I didn't want to do that if it needed a 30 or 40 and I was going to upsize it????
 
paulpowell3540 said:
Thanks for you help - I don't run the fuel out - only at the end of summer when its going into winter store under the carport, so it would have fuel sitting in the carbs sometimes for several months, its performed like this since Ive had it but as its my first boat I assumed this was it! - I don't use it all that much except of late Ive had it on the water a bit more and noticed other similar sized boats with a 25HP doing much more than mine so I started to ask people on the water and they tell me one of two things (1) the carbs need cleaning or (2) you need a bigger engine - Honda 4 strokes are not as good as 2 stroke!! - its a trailer boat so the alluminium hull is fine and clear - Im pretty sure its sparking on all three (new plugs last service) as it runs quiet and smooth - The gear engage/throttle goes from vertical - forward 45 degrees - It accelerates up to a bit over halfway but when I push it down the remainder forward - nothing happens in revs increase or speed.
I am happy to spend money on a carb clean and tune/balance as long as it will perform but I didn't want to do that if it needed a 30 or 40 and I was going to upsize it????
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Also it has always been serviced every six months even if its not being used - I don't know if they do much more than an oil change though?

15 knots is tops and it hovers between 13/15 knots WOT depending on the wind - thats with two adults a battery and 20 lts fuel - I just put in 98 octane fresh stuff - no difference
 
I don't know a thing about the Honda 25, but from everything you have described I would suspect that your prop is too small in terms of diameter, pitch, or both. Hopefully, someone on this thread can tell you how to hook up a tachometer to that engine for an on-water test. Your operator manual will tell you the rpm's your are supposed to be getting at wide-open throttle (WOT - 6000 rpm's for most of the bigger Honda's.) Your engine has a limiter so it will not go over WOT, so that would explain why you get up to speed, but additional throttle doesn't get you going faster. In the meantime, look for folks that have a similar setup and ask them the prop diameter and pitch they are using. If you have a good realtionship with a nearby Honda dealer, they will often loan you a prop or two for testing purposes.
 
I own a BF25 and it pushed along a 13ft Dory hull without any problem once i put the carbs through my ultrasonic cleaner and replaced the carb manifold to engine gasket as it had a leak there. As your hull is aluminium then it`d be much lighter than the fiberglass dory so it shouldn`t struggle at all pushing it along.

Each carb has to be drained after every trip otherwise over time the jets will varnish up and reduce your engines performance and if the carbs are taken off then new gaskets are essential even though they cost a fair bit. Pay particular attention to the emmulsion tubes for tiny hairline cracks as the might not look anything bad but when fuel is forced by at pressure then it sprays everywhere affecting performance again.

In regards to a tacho then get yourself something like this which can be picked up really cheaply and are the same as yamaha`s own one without the name and price tag. http://www.ebay.co.uk/itm/Tach-Hour...71?pt=UK_Motorcycle_Parts&hash=item230f580a2b

Hopefully when you get a tacho then it`ll give you an idea of WOT and what your engine is doing as without one then you`ve no idea really what is going on and essential in regards to re-propping your engine to suit you boats length and weight.

Cheers, Matt.
 
matt.speedtriple said:
I own a BF25 and it pushed along a 13ft Dory hull without any problem once i put the carbs through my ultrasonic cleaner and replaced the carb manifold to engine gasket as it had a leak there. As your hull is aluminium then it`d be much lighter than the fiberglass dory so it shouldn`t struggle at all pushing it along.

Each carb has to be drained after every trip otherwise over time the jets will varnish up and reduce your engines performance and if the carbs are taken off then new gaskets are essential even though they cost a fair bit. Pay particular attention to the emmulsion tubes for tiny hairline cracks as the might not look anything bad but when fuel is forced by at pressure then it sprays everywhere affecting performance again.

In regards to a tacho then get yourself something like this which can be picked up really cheaply and are the same as yamaha`s own one without the name and price tag. http://www.ebay.co.uk/itm/Tach-Hour...71?pt=UK_Motorcycle_Parts&hash=item230f580a2b

Hopefully when you get a tacho then it`ll give you an idea of WOT and what your engine is doing as without one then you`ve no idea really what is going on and essential in regards to re-propping your engine to suit you boats length and weight.

Cheers, Matt.
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Thanks Matt
It seem the motor IS big enough which was my concern - I did not want to spend money having the carbs cleaned/balanced if it were too small but I will now put it in to a Honda dealer and have this done also have the prop checked - come to think of it, it does throw up a big "V" and a lot of wash for very little forward momentum!
 
One other thing occurred to me. Check how your engine ismounted. The anti- cavitation plate should be just skimming the top of thewater at full power. Also, check your trim. If your trim is set too low (proptilted too far inward) that will cause the boat’s bow too low and push morewater than necessary. If it is set too high, that will raise the bow too much.Either will impact performance.
 
Thanks to all who helped - I had a marine mechanic take the carbies off and the bottom one was full of green slime - Its been firing on two instead of three for years!!!!

Now goes like HELL
 
As above and enjoy the new found power from your engine but mind to drain the float bowls after each trip. It only takes a couple of minutes and will save you any further carb problems hopefully.

Cheers, Matt.
 
matt.speedtriple said:
As above and enjoy the new found power from your engine but mind to drain the float bowls after each trip. It only takes a couple of minutes and will save you any further carb problems hopefully.

Cheers, Matt.
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I've heard of this procedure many times and never done it.
my motor runs fine often sitting for a couple of weeks at a time.
Is this really necessary ?
 
dark_star said:
I've heard of this procedure many times and never done it.
my motor runs fine often sitting for a couple of weeks at a time.
Is this really necessary ?
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With modern fuel then yes it is. There`s so many additives now that when it`s left sitting in the float bowls then it`ll start to evaporate and thicken up slowly, the holes in you carbs and jets get restricted although you might not notice it until it`s too late. Hence all the threads about blocked carbs and having to strip them. Better a two minute job draining them, rather than the hassle and cost of stripping carbs and replacing gaskets.

Cheers, Matt.
 
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