difference between honda bf75/90

[breezeblock]

heres a bit of a question for tonight what is the difference between hondas bf75d and 90d engines i have had a look at both their specs and they are identical in every way but that doesn't tell me why their outputs are different so is it camshafts head design rev limit or what

[jyasaki]

Can I be the first to say "15"?

I think (I am not at all sure of this) that the ignition/injection map is different. Done to fill the hp niche for different power levels.

jky

[jeffstevens763@g]

I was told that a yam 13 hp was made for a certain market and the Rev limiting screw was adjusted to make it a 15 hp again. I would guess the CDI would be different as said, I know the Suzukis in the 90 hp range I think 80,90,100 1500 cc are the same engine so tuned to increase hp.from the manufacturers point of view easy to make the same engine with slight changes to gain 10 hp I suppose?

[breezeblock]

spoke to the dealer today and he reckoned that it was ecu and injectors so it sounds cost prohibitive

[jeffstevens763@g]

what kind of dosh they talking out of interest

[breezeblock]

2k approx for ecu and 300 each for injectors

[jeffstevens763@g]

Honda 80 £7935 100 £8165 new Ron hale marine prices thats getting well up toward those prices for the bits

[breezeblock]

yes i know thats why i am thinking sell the old boat with engine complete and fit new engine onto new boat with the cash from the sale

[alystra]

I have a year 2010 BF90. The manual, which covers the BF75 too, says the 75 is a standard OHC engine, while the 90 is OHC VTEC. I was told that until you get beyond 4.500 rpm, there is little difference between them in torque/power.

[breezeblock]

Originally Posted by alystra

I have a year 2010 BF90. The manual, which covers the BF75 too, says the 75 is a standard OHC engine, while the 90 is OHC VTEC. I was told that until you get beyond 4.500 rpm, there is little difference between them in torque/power.

how do you find the 90 on your humber what length is it

[alystra]

[QUOTE=breezeblock;727934]how do you find the 90 on your humber what length is it[/QUOTE

Destroyer 5.3 metres. The boat was originally supplied with a Mercury 90hp four stroke in 2000. I broke the gearbox on that. :-(

Compared to the Mercury, the Honda is considerably lighter, which upset the balance of the boat noticeably. (ISTR Humber vary the position of the console and tank to get the correct fore and aft CoG and mine is placed well forward to balance the heavy Mercury) I corrected the trim by stowing the little dinghy I carry aft instead of forward.

The Honda is much quieter. Optimum revs. for economy seem to be 4200-4400, about 500 higher than the Merc. The Honda seems to have less torque at low speeds, but you can feel the 'punch' when the VTEC kicks in around 4,500 rpm. At high speeds it is less thirsty, but fuel consumption seems about the same, or only slightly better, than the Merc at cruising speed.

I usually cruise at between 4200 and 4400 rpm, giving between 23 and 25 knots. My average fuel consumption is 1.40 miles per litre, 0.71 litres per mile, 8.42 litres per hour.

I'm not sure I like the separate trim and tilt rams, compared to the Mercs single ram, but that's a minor niggle. There are lots of fish farms around here, and Honda is the engine of choice for all their small craft.

I'm very pleased with mine.

[breezeblock]

[QUOTE=alystra;728004]

Originally Posted by breezeblock

how do you find the 90 on your humber what length is it[/QUOTE

Destroyer 5.3 metres. The boat was originally supplied with a Mercury 90hp four stroke in 2000. I broke the gearbox on that. :-(

Compared to the Mercury, the Honda is considerably lighter, which upset the balance of the boat noticeably. (ISTR Humber vary the position of the console and tank to get the correct fore and aft CoG and mine is placed well forward to balance the heavy Mercury) I corrected the trim by stowing the little dinghy I carry aft instead of forward.

The Honda is much quieter. Optimum revs. for economy seem to be 4200-4400, about 500 higher than the Merc. The Honda seems to have less torque at low speeds, but you can feel the 'punch' when the VTEC kicks in around 4,500 rpm. At high speeds it is less thirsty, but fuel consumption seems about the same, or only slightly better, than the Merc at cruising speed.

I usually cruise at between 4200 and 4400 rpm, giving between 23 and 25 knots. My average fuel consumption is 1.40 miles per litre, 0.71 litres per mile, 8.42 litres per hour.

I'm not sure I like the separate trim and tilt rams, compared to the Mercs single ram, but that's a minor niggle. There are lots of fish farms around here, and Honda is the engine of choice for all their small craft.

I'm very pleased with mine.

what is the performance like as i am unsure that the bf75 will have enough oomph

[alystra]

[QUOTE=breezeblock;728048]

Originally Posted by alystra

what is the performance like as i am unsure that the bf75 will have enough oomph

Max speed I've managed, with a lot of gear aboard, (camping stuff, boat tent, 80 litres fuel, heavy ground tackle) is 39 knots. I hardly ever go there.

I changed the prop to a Solas Rubex 13.2 x 19 inch pitch. This is perfect for the boat as I use it, but with four people aboard including me, she takes a while to get over the hump and on the plane. With five hefty passengers plus me, she won't get going. Even at full throttle, the revs. won't climb high enough to get any power.

However, with the supplied Honda 17 inch pitch prop she took off like lightning, was under propped for my usual load, and would have probably managed the five heavy chaps quite well. It's that experience that makes me think that, compared to the Mercury, this engine doesn't have as much torque at low revs. At medium and high revs. I think the Honda is better and more responsive - but that may be because it's the engine I chose.