90 or 70 hp 4 stroke motor for 170cc

[mikey416d]

i am in the process of purchasing a 170 dc with a 70 yamaha 2s.
i could also have a yamaha 60 4s put on instead.Do not want to add the extra weight
but worried about polution.Some Help?

[JETPILOT]

Originally Posted by mikey416d

i am in the process of purchasing a 170 dc with a 70 yamaha 2s.
i could also have a yamaha 60 4s put on instead.Do not want to add the extra weight
but worried about polution.Some Help?

I know your looking at yamaha but have a good look at the Etec as an option because I think they produce less emissions that 4 stroke.More power responce and less weight...

Cheers Paul

[Ron's 195DC]

Both the Yamaha 4s and the Evinrude E-tec score a "three star" on the the California CARB rating scale. So emmisions are both "ultra low". The reason why I went with the Yamaha is because the local Triumph dealer carried them. The other option was a Honda, but that dealer was about 70 miles away. I really don't think you can go wrong either way. All are excellent engines, with proven technology. If I were you, I'd go with an engine that can be serviced locally.

Good Luck,
Ron

[Ron's 195DC]

Opps, Sorry. I forgot to add that the Yamaha HPDI 2 stroke has a CARB rating of "two star". So a Yamaha 4s or an E-tec are cleaner burners.

[jconstab]

I have a 50hp Yamaha 4 stroke on my 17" and while it gets me around, I consider this boat to be underpowered. WOT by myself I run 30mph and with 2 people around 26-27. The plus is I don't burn much gas but it is harder on the motor when you have to run it full speed all the time.

A 70 hp should have plenty of power and still be gas-efficient. The 70 should be more than enough power, good on gas, light-weight, and less money.

Seems to me like a 90hp would be a lot of power for that little boat. The weight difference isn't that great but I don't think you would really need the extra 20hp.

[Deltaviller]

and 1 aboard, 1/2 tank fuel. This is with a hydrofoil on the motor plate. I think the hydrofoil might be increasing my top end 3 mph because reviews Ive seen online call for a top end of 32 or 33 with this motor. I have been very very pleased with hydrofoil, installed by dealer when I bought the boat as a no cost option, at least not itemized. I am on plane at a little over 3000 rpm, also quicker than with no hydrofoil, I suspect.

Anybody else have thoughts on these hydrofoils, pros or cons?

Also, are the yamaha speedos considered accurate or do they perhaps have a built in error maybe + 10 percent? I know Japanese motorcycle speedos read high, thats why I ask.

[fridaysoff]

Deltaviller,
Speedometers on boats are usually unreliable. GPS speed is more accurate. I had a 2004 170CC with a 60HP Yamaha 4 stroke. I could get 37 MPH (GPS) with 1 adult, full tank of fuel. I put a Bob's machine shop Stabilizer plate on my motor. I really liked it. I don't think it added any speed to the boat but it allowed me to plane at a slower speed which was good on rough water days. I think it looked a lot better on the engine.It had a smaller profile that the whale tail looking hydrofoils. Price was about the same.
John D.

[Deltaviller]

Thanks for the info Fridaysoff. You are doing well with your 60 hp at 37 mph on a GPS! Must have a barnacle free bottom, maybe teflon coated even. With a couple weeks growth of barnacles, my top speed drops down to 26 mph or so indicated. I kind of enjoy scraping them off for some strange reason, at least in the summer when the waters warm so I havent used bottom paint. Takes less than an hour to scrap them off every 3 days or so. Other times I just pull it up on the trailer to avoid buildup.

[Deltaviller]

On the subject of 70 or 90 hp 4 strokes for the 170, I'd watch the weight so you don't overload the back end for optimal attitude/angle in the water. Although with a hydrofoil on the motor you could probably compensate for the added weight, raising the stern some at speed.

I'd look at the Nissan 90 if I was to consider turning my 170 into the fastest boat it could be. I think it weighs in around 315. 2 stroke but direct fuel injected and 2 star rated environmentally.

[Ozy Mark]

Hi All,
It was always a big decision as to what motor to fit to any new boat. Lets see Fuel Consumption, Emmision, Noise, power to weight, Performance, Warranty. Thats why I chose a Evinrude E-tec 75HP. Plus NO run in time, No service for 3 Years, and 3 years warranty. Its power curve is just awesome allowing me to use it as a skii boat as well. 17" SS prop stock and at you can select pitch to suit speed or power. 15 Pitch sits at around 5500RPM (great power) and 17Pitch sits at 5100RPM (great top end speed). Also have a specific prop being made for just skiing by Solas props here in Australia. I fished alot with a Yamaha 60 on a 17' alley boat and it always suffered with cavitation in the rough as it got sucked back into swell at low speeds. With the Evinrude E-tec it has so much bottom end power it can push that 17" prop and overcome that swell. Thats confidence! And finally, apart from voiding your warranty putting a 90HP on the back of a new 17DC, the power curves on the Evinrude E-tec 75 and 90 are so close its not worth all the extra dollars for very little end gain.

Hope this may help someone who is on the doorstep of engine decision time, as its 130Hrs in and still running like the day I got it

Cheers
Very Happy
Ozy Mark