90hp yamaha vs. 70hp evinrude

[JKTrevecca]

Considering upgrading to more power. I currently have a 94 70hp evinrude 2-stroke on a 16 foot deep v smokercraft. I could swap (for little to no money) for a 98 90hp yamaha 2-stroke. Any thoughts on the differences in reliability of these two? I currently get 37-38 MPH top speed on the 70hp. How much more could I expect from the 90hp?

Thanks in advance!

-- Jason

 

[robert graham]

Well, I've been running a 1999 C90 since I bought it new and it's got plenty of power for my 1870 Jon boat....never a problem with this motor....You'd probably notice quite a difference from your 70HP motor....the older 2 stroke carbed motors just seem to pull stronger than the 4 strokes, especially from a standing start....at least they sound stronger.....

 

[smittylv1]

C90 Yammie is an awesome motor, especially coming out of the hole...but the fuel economy is terrible compared to a four stroke.

 

[robert graham]

C90 Yammie is an awesome motor, especially coming out of the hole...but the fuel economy is terrible compared to a four stroke.

Yep, they like the gas....that's why I usually cruise in the 3500 RPM range....simple/dependable motors!.....

 

[JKTrevecca]

Well I went and looked at the boat/motor today. The motor serial # ends in a "j" which tells me it's a 1986, not a 1998 model year. I tested the compression cold and got 115, 115, and 120. I primed it, choked it, and it started immediately. Goes into gear fwd and reverse as expected. But........ It started to miss on 1 cyl after running for a little while. If I squeeze the bulb a couple times, it smooths back out. This tells me it's not getting fuel and after it burns the fuel in the bowl from being primed, it's missing.


The motor looks great and comes with guages, full controls, and the boat and trailer. I need to decide if I'm going to go for it and trust I can remedy the fuel supply issue. The owner has a receipt from 3/2014 from a legit marina that rebuilt the carbs, replaced the fuel line, and changed the lower unit oil. It runs fine until it starts missing.

Any thought/idea's/suggestions? Is what I'm describing a sign that it could have been run hot at some point or does is sound 100% fuel related?

Thanks!

 

[robert graham]

Well I went and looked at the boat/motor today. The motor serial # ends in a "j" which tells me it's a 1986, not a 1998 model year. I tested the compression cold and got 115, 115, and 120. I primed it, choked it, and it started immediately. Goes into gear fwd and reverse as expected. But........ It started to miss on 1 cyl after running for a little while. If I squeeze the bulb a couple times, it smooths back out. This tells me it's not getting fuel and after it burns the fuel in the bowl from being primed, it's missing. The motor looks great and comes with guages, full controls, and the boat and trailer. I need to decide if I'm going to go for it and trust I can remedy the fuel supply issue. The owner has a receipt from 3/2014 from a legit marina that rebuilt the carbs, replaced the fuel line, and changed the lower unit oil. It runs fine until it starts missing. Any thought/idea's/suggestions? Is what I'm describing a sign that it could have been run hot at some point or does is sound 100% fuel related? Thanks!

May just be a bad fuel pump diaphragm....easy check/easy fix....

 

[99yam40]

buying a motor with a problem and hoping for an easy fix is not the smart thing to do.

If it was easy why does he not fix it to begin with