75hp vs 90hp

[196thDLR]

I am trying to figure out what the differences are in a 2003 Yamaha 75hp 4S Tiller, vs a 90hp. According to my manuel, the the weight, cylinder displacement, stroke and compression ratio is the same. Does anyone of the FM viewers know?

[196thDLR]

Anyone??

[JohnMickish]

I'm not positive here but guessing simple stuff like injector flow rates, camshaft and programming.

[slammer]

Try this under the boats and motors forum. Might get more answers. I would guess the only differance would be the fuel system since all else is the same.

[marine_man]

It's in the fuel system... the block is exactly the same.

marine_man

[SkunkedAgain]

When I was buying my Suzuki this year, it was the same thing. The 70hp, 80hp, and 90hp motors were all the same block but tweaked differently for more power. It made me wonder what I was exactly paying for (in terms of physical changes) for the 20hp upgrade!

[marine_man]

On an EFI Software Mappings.. and that's probably about it!

marine_man

[solbes]

So a 2008 Yamaha 75 EFI is only different from the 90 in the ECM?

[marine_man]

Very Likely just a different fuel map. Possibly different injectors, but most likely a different programming.

Prior to EFI it was different carbs or restrictor plates, but that's about it.

marine_man

[Black_Bay]

Occasionally the exhaust is different. Some smaller outboards, like 9.9 hp, can be modded to 15 hp by doing that.

[196thDLR]

Thanks for the answers guys. Now, my question is, can the parts be purchased changing an 75hp to a 90hp?

[Black_Bay]

I'd contact Hydro Tech Marine.

[solbes]

Let us know what you find out. My warranty is out in a little less than 2 years, hehe.

[marine_man]

I'm sure you could... especially if you were willing to spend the time comparing part numbers between models, etc.

It might be interesting to get it worked on by a dealer and making sure you get the right parts...

marine_man

[196thDLR]

Thanks again guys. I'll keep you posted when I find anything.

[Gator Slayer]

I read on another forum the only difference is an obstruction in the intake of the 75hp motor. It's a small disc that can be removed. The computer reads the airflow through the intake to determine fuel delivery and the computer "learns" as it goes. Not sure if it's 100% accurate but the guy who said this is an accomplished motor guy and does R&D for some of the MFR's. It's probably worth a look in the intake.

[JohnMickish]

Back in the day when car makes would offer the same engine with multiple HP ratings it was quite involved. Intakes, carbs, heads, compression ratio and cams where often all different.

Would be cool if it where as simple as a ECM change, but whats the cost of an ECM and would you really be saving any money by doing it that way?

[SkunkedAgain]

Gator Slayer, as mnfishingguy said it's probably a combination of things. The guy who was "an accomplished motor guy" probably boiled it down to essentially saying that there is a restrictor plate/disc for simplicity sake.

In the end, I'm sure that a knowledgeable service tech could tweak out a 75hp to a 90hp motor for less than the dealer charges. However, for all that I'll pay the extra cash to just get the 90hp if that's what I want.

[Gator Slayer]

Well the guy is a world champion, world record holder in USA powerboating. He also does R&D for Merc. and has done some testing for the others. If I were you I'd look in the intake and if you find an obstruction pull it. If you get better performace, question solved at no cost. If you think it's not helping then I'd try a dealer. If you would like I can post the question on the "refuge forum" and see if Danny will answer it.

[196thDLR]

GS: Please do so. I greatly appreciate your offer.

[Gator Slayer]

Here's a pic of the metal rest There you go. Worth a try in my book. Let us know how it goes if you do it.

[note from admin: please read forum policy before posting again. thanks!]

[311Hemi]

Well the guy is a world champion, world record holder in USA powerboating. He also does R&D for Merc. and has done some testing for the others. If I were you I'd look in the intake and if you find an obstruction pull it. If you get better performace, question solved at no cost. If you think it's not helping then I'd try a dealer. If you would like I can post the question on the "refuge forum" and see if Danny will answer it.

US-1 does know what he is talking about based on the things I have read from him. I guess if it were me I would think about giving it a shot.

[196thDLR]

GS; I deeply appreciate your help and the responses of everyone else. Thanks again.

[Gator Slayer]

You're welcome. Glad to help. If you go to the thread on refuge forums it's been quite popular. Turns out this trick may work on lots of engines. One caveat. You may need to disconnect the battery to get the ECU to "forget" its memory.

[TROUTTEASER]

That is for an efi engine, correct? 2003 yamahas are carburated, so I'm guessing there is more to it?