Honda 75 to 90 hp boost

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phatmanmike

Captain
Joined
Oct 24, 2003
Messages
3,869
Re: Honda 75 to 90 hp boost

its actually cheaper to sell it and go buy a 90hp.<br /><br />good luck, but you will fail my friend, many have had this idea. all were wrong
 
Triton II

Triton II

Commander
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Nov 23, 2004
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Re: Honda 75 to 90 hp boost

good luck, but you will fail my friend, many have had this idea. all were wrong
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Why? I'd love to know MOB, so please enlighten us. It would seem simple given the basic specs of both motors.<br /><br />BF75:<br /><br />ENGINE<br /> <br />Type: 4-stroke SOHC 4-cylinders<br /> <br />Displacement: 1590cc<br /> <br />Bore & Stroke: 75 x 90 mm <br /> <br />Full Throttle RPM Range: 5000-6000 RPM<br /> <br />Rated Power: 75HP @ 5,500 RPM<br /> <br />Cooling System: Water cooled<br /> <br />Induction: 4 Carburettors<br /> <br />Ignition System: Capacitor Discharge (CDI)<br /> <br />Starting System: Electric<br /> <br />Exhaust: Through Prop<br /> <br /><br />BF90:<br />ENGINE<br /> <br />Type: 4-stroke SOHC 4-cylinders<br /> <br />Displacement: 1590cc<br /> <br />Bore & Stroke: 75 x 90 mm <br /> <br />Full Throttle RPM Range: 5000-6000 RPM<br /> <br />Rated Power: 90HP @ 5,500 RPM<br /> <br />Cooling System: Water cooled<br /> <br />Induction: 4 Carburettors<br /> <br />Ignition System: Capacitor Discharge (CDI)<br /> <br />Starting System: Electric<br /> <br />Exhaust: Through Prop<br /> <br />Apart from the quoted power output they seem to have the same capacity etc. So some info would be helpful (I'm considering a Honda BF90 so this is a genuine question).
 
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Joe Merchant

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Jan 11, 2005
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Re: Honda 75 to 90 hp boost

I know you can do that little trick to a 40 to 50. I was told by a mechanic that it would cost about 1500 bucks. But the dealer wouldn't touch it afterwards as far as warranty or service. <br /><br />Maybe an option on an older engine. ??
 
Silvertip

Silvertip

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Sep 22, 2003
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28,762
Re: Honda 75 to 90 hp boost

Every car manufacturer has at least one base engine but can get several horsepower ratings from that engine by manipulating cam lift and duration, valve sizes, intake air flow, compression, carburetion, ignition, and exhaust and that's just the major components. Outboard manufacturers do similar things. Every manufacturer usually has two or three horsepower ratings for a block with the same displacement. It's not just decals and 10 bucks worth of carb jets. If it were that simple, dealers would sell none of the larger engines as everyone would by the smaller one and simply "hop it up". It is very inexpensive for the factory to make these changes during the production process. It is very expensive to make the mods after the fact.
 
MajBach

MajBach

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Jun 21, 2003
Messages
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Re: Honda 75 to 90 hp boost

Different cams if memory serves, for starters. But there are experts here that would know this for certain. IT is true, it's not just a decal that sets them apart. Look at MErc old 2-strokes: they had one block for their 115 all the way up to 250hp. It may be just general interest for you, but I'm sure many would agree that these forums are often the best source for info as they are baed on experiences, not knowledge and opinions alone. Go with that and understand you are but one of many that has posed this question before - the answer is still the same.
 
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phatmanmike

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Joined
Oct 24, 2003
Messages
3,869
Re: Honda 75 to 90 hp boost

Go with that and understand you are but one of many that has posed this question before - the answer is still the same.
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But the dealer wouldn't touch it afterwards as far as warranty or service. <br />
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If it were that simple, dealers would sell none of the larger engines as everyone would by the smaller one and simply "hop it up"
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i could not have said it better myself. thank you
 
I

ivar

Petty Officer 1st Class
Joined
Jul 30, 2002
Messages
208
Re: Honda 75 to 90 hp boost

Originally posted by MajBach:<br /> Look at MErc old 2-strokes: they had one block for their 115 all the way up to 250hp.
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Really? As far as i know, 90-140 used the IL6 block while the larger engines used 2.0L or 2.5L V6 blocks.
 
MajBach

MajBach

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Jun 21, 2003
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Re: Honda 75 to 90 hp boost

Thats what I thought too until I saw specs for a buddy's 100 hp (mid-80s).
 
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OBMD

Seaman Apprentice
Joined
Sep 2, 2001
Messages
46
Re: Honda 75 to 90 hp boost

I ran the part numbers. Cam is the same. ECM is the same. Carbs are different and cost almost $1800 retail. Trade the 75 for a 90.
 
N

Navigator

Chief Petty Officer
Joined
Feb 6, 2001
Messages
517
Re: Honda 75 to 90 hp boost

Dont forget the valves? On the 40 to 50, the valve size changed as well, thus making it too expensive to enact the upgrade. I assume the 75 to 90 probably has the same change too. The best way is to get the microfische and compare part numbers.<br /><br />Nav :cool:
 
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