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Yamaha 90 2 stroke

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Yamaha 90 2 stroke

Postby mitch184 » Wed Feb 07, 2018 3:32 pm

Yamaha 90hp 2 stroke jet. Anyone running one? I think they did offer a 90/65 for couple years, but most are the 90 powerhead and decal with a pump.

If so, how big of a boat and how fast does it run?

Thanks
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Re: Yamaha 90 2 stroke

Postby Stof » Sat Feb 10, 2018 10:04 am

I have a 18 foot open boat with a 2005 65/90 Yamaha tiller. It goes 30 at tide open with just me in the boat and fishes one other well when side drifting. It will run 3 people up river max the motor has been super reliable even though it was sank while running. That is max hp for my hull or I would go bigger.
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Re: Yamaha 90 2 stroke

Postby mitch184 » Sun Feb 11, 2018 8:42 pm

Thanks. And it is/was the 2 stroke?

What kind of 18' foot boat? Alumaweld? Any idea on the weight of it?
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Re: Yamaha 90 2 stroke

Postby Stof » Mon Feb 12, 2018 1:17 am

Yes
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Re: Yamaha 90 2 stroke

Postby mitch184 » Tue Feb 13, 2018 4:44 pm

Thanks. I sent you a PM for more details
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Re: Yamaha 90 2 stroke

Postby handyandy » Tue Feb 27, 2018 12:14 pm

one of the best two strokes made power to weight wise.
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Re: Yamaha 90 2 stroke

Postby mitch184 » Wed Feb 28, 2018 5:16 pm

Yes Sir. It's shame none of the manufacturers have come out with anything even remotely close to that weight since. A < 300# 90 HP outboard would clean up on the market right now.
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Re: Yamaha 90 2 stroke

Postby handyandy » Thu Mar 01, 2018 9:12 am

it was one of the weaker 90hp as it was the lowest displacement one where as omc 4cyl 90's shared the same block/displacement with the 115hp's so they were big 90's the yamaha 90 was the same block/displacement as the 3 cyl 75hp of the time, but none the less a great engine I would like to have one if I could ever get my hands on a cheap one, but people always want a lot for a decent one let alone the cost of a tiller and jet pump for it. I'm not saying it's a weak motor just stating that compared to other 90's that weighed more at the time it's because the most other 90's were essentially detuned 115's. Hard to beat a good simple inline 3cyl two stroke.
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Re: Yamaha 90 2 stroke

Postby mitch184 » Thu Mar 01, 2018 3:44 pm

They are a weaker 90. I seen 84-85hp brought up. Plus it doesn't hit that until a little higher RPM than a jet usually lets it spin up. I think that's more the reason why people think they are weak. The Merc 90 makes a little over 90hp but at only 4900-5000. So all that power is available with a jet.

You're right about hard to find a cheap one. I'm looking at selling my low hours 115 Optimax and I'm afraid it'd be a wash to put a Yami 90 on there!
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Re: Yamaha 90 2 stroke

Postby Crawdad Johnny » Fri Mar 02, 2018 7:56 am

Mitch - I'm curious as to why you are considering selling your low-hours 115hp Optimax?
17 Ft Wooldridge Alaskan
150/105HP Mercury Optimax, Flow-Tec Quick Steering
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Re: Yamaha 90 2 stroke

Postby mitch184 » Mon Mar 05, 2018 10:47 am

Shave some weight off the boat. Mainly a small river boat, floating shallow is more important that going fast. Save around 200lbs by switching. Motor, battery, wiring, etc.

Just an idea if the right deal came along. And I realize that the 115 Opti's are the best 115 ever built. Power and fuel consumption wise. Just more than I need and honestly all those moving parts scare me a little.

"Low Hours" being around 250 for a 2009 motor.
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Re: Yamaha 90 2 stroke

Postby handyandy » Tue May 01, 2018 10:36 am

the yamaha 90's are darn good engines, I'd like to have one with a tiller and jet on it would be a great motor for a 1854 to 1860 size boat. But I'm to cheap for what people usually want out of let alone most I find are props and I'd have to convert it. But darn good motors and they can be modded pretty well to make some good power for their relative size. But if you already have a 115 opti I don't know that I'd bother switching unless you just want a simpler and lighter engine. It won't push the boat as well.
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Re: Yamaha 90 2 stroke

Postby Stof » Tue May 01, 2018 6:16 pm

handyandy wrote:the yamaha 90's are darn good engines, I'd like to have one with a tiller and jet on it would be a great motor for a 1854 to 1860 size boat. But I'm to cheap for what people usually want out of let alone most I find are props and I'd have to convert it. But darn good motors and they can be modded pretty well to make some good power for their relative size. But if you already have a 115 opti I don't know that I'd bother switching unless you just want a simpler and lighter engine. It won't push the boat as well.


What are these modes you speak of ?
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Re: Yamaha 90 2 stroke

Postby handyandy » Wed May 02, 2018 6:31 am

Shave the head a little for more compression, better reeds like chris carsons, bigger jets in the carb, better exhaust tuner, some porting if you want to tear into it. Hydro Tec marine does some good work on yamie power heads. They sell a pretty easy to install kit, or you can send them a powerhead and do some port work. https://www.shop.hydrotecmarine.com/pro ... tegoryId=2
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Re: Yamaha 90 2 stroke

Postby mitch184 » Wed May 02, 2018 4:06 pm

Oh yeah, once I track a 90 down, it won't stay stock.

Bump the compression, light porting and timing adjusted, CCM reeds, one size bigger jets in the carb, lightened flywheel, etc. Match that to a pump with a lightened 4 blade impeller and worked over housing and I'm guessing I'll be seeing basically the same performance as I'm seeing now with the 115. Once you factor in the weight loss too. Will have mid housing cut down to a 15" shaft if I put a tunnel in at the same time.

The once the tunnel goes in and thermolite floors installed.... it'll be right where I want it.
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Re: Yamaha 90 2 stroke

Postby handyandy » Thu May 03, 2018 6:14 am

I'm not a big tunnel fan, but that's just me. I'd like a yammie 90, but they're usually to rich for my blood. Cutting a mid is a bit of work not sure that I'd mess with that, but I could see why you would want to with how high the transom would be with a tunnel.
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Re: Yamaha 90 2 stroke

Postby handyandy » Thu May 03, 2018 6:19 am

etec 90 is about as close as you can come anymore now in terms of size and weight to old yammie two stroke 90. But the yammie is still a decent bit lighter, have to admit if I went for a newer engine it would be an etec 90, something about inline 3 engines just simple and easy.
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Re: Yamaha 90 2 stroke

Postby mitch184 » Thu May 03, 2018 9:12 am

I'd agree, if I HAD to go brand new, etec 90 would be my only option until someone builds a 4 stroke of equivalent weight. Mercury is getting close.

Cutting the mid's, for a jet, is actually fairly basic if you find the right guy. There's a guy in Louisiana I'm working with about getting a motor built. Plus when you shorten the mid, you could swap out to the smaller trim/tilt, which saves another 20-25lbs I believe, if you wanted. 110hp out of a 240lb motor..... what's not to like about that.. :)

Why are you not a fan of the tunnels? Just out of curiosity... I've had a couple of both and have my own drawbacks, but curious to see what yours are.
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Re: Yamaha 90 2 stroke

Postby handyandy » Fri May 04, 2018 8:24 am

Cause I've mostly had flat bottoms which if set up right with no tunnel the shoe barely hangs down any I've hardly had issues hitting the shoe, when I have I imagine I would have hit with a tunnel as well. The protection tunnels provide tend to sacrifice some speed, and seem to usually increase the time to plane out it. Boats initially designed with a tunnel seem to do well, but most I've seen added in after the fact always seem to be rather performance robbing. Bigger boats with big obj seem to be much better with them, but seems any smaller rig running a 60/40 are usually a decent bit slower than a similar rig without a tunnel. Just been my experience and personal observations, I know there are advantages a tunnel provides. I've never personally never really needed those advantages enough to sacrifice the performance loss by adding a tunnel. To me it seems unless you really need a tunnel I wouldn't want one. That's just my opinion based off what I've seen and experienced, I'm not dogging anyone with a tunnel, as I'm fully aware of the benefits a good tunnel can add.
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Re: Yamaha 90 2 stroke

Postby mitch184 » Fri May 04, 2018 12:32 pm

People talk about a deeper draft, but when floating at rest, but it's truly only about 1/4" deeper worst case. At REST.....HOWEVER.... when getting on plane and only the back end of the boat is in the water.... that's where that additional draft becomes greater. Hence the slower holeshot unless you adjust to compensate.

In my case, I add a transom wedge to help try and help with holeshot. However, by the time you trim all the way out when running, your're right, the pump doesn't actually hang down much below the bottom.

Would be interesting to have the same boat both with and without a tunnel to see the differences.
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