2 stroke 4 stroke ?s

[settnhooks]

I have a 1975 Evinrude 9.9 2 stroke, runs great. But, I want to cruise a good distance without going deaf or loosing the feeling in my left arm. Plus given the age of the motor, despite it running great, still doesnt give me a lot of confidence to go real far. So Im in the market but have some questions... I have searched but my questions are a little specific to my situation.

-Is an newer (5 years old non DFI/FI) 2 stroke 9.9 or 15 going to be quieter than my old 75 rude 2 stroke? A coworkers friend said his 15hp 2 stk Yamaha is really quiet and he would let it go for 500!! Crazy deal so I might not pass it up regardless of matching my exact wants... bieng best of both worlds

-Will a 4 stroke 15hp not be any faster than a 9.9 2 stroke given weight, RPMs and hole shot?

-Does anyone even make a 9.9 2 stroke with DFI/EFI? Seems like they all start in the 15 to 30 hp range.

Thanks for any replies.

 

[Sea Rider]

Re: 2 stroke 4 stroke ?s

Some answers & Welcome to the Forums...

-2 strokes old or new are noisier, not unconfortable though to ear, than 4 strokes.
-A 15 HP 4 strokes is slight faster, has better hole shot, pushes more weight than a 2 strokes 9.9.
-Weights about 10 KG more compared to a 2 strokes 9.9/15 HP
-Check that Yamy 15, good deal, if possible test and compare to your actual 9.9.
-Keep that beloved 9.9 oldie as spare, you never know...

Happy Boating

 

[settnhooks]

Re: 2 stroke 4 stroke ?s

Some answers & Welcome to the Forums...

-2 strokes old or new are noisier, not unconfortable though to ear, than 4 strokes.
-A 15 HP 4 strokes is slight faster, has better hole shot, pushes more weight than a 2 strokes 9.9.
-Weights about 10 KG more compared to a 2 strokes 9.9/15 HP
-Check that Yamy 15, good deal, if possible test and compare to your actual 9.9.
-Keep that beloved 9.9 oldie as spare, you never know...

Happy Boating

Thanks for the info Sea Rider.

Have there been any advancements in the cowling to sound proof the loudness of more modern two strokes or it is marignal at best and will still be pretty loud?

Do you really think a 15hp 4 stroke will have a better hole shot than a 9.9 2 stroke? I kind of thought they might be about the same, especially given that it will be adding an additional 45-50 lbs to a 1436 aluminum jon and RPMs will be lower. Again, 500 for a 5 year old 15 2 stroke may be too good to pass up and I will learn to love the loudness.

 

[whofan]

Re: 2 stroke 4 stroke ?s

I have used a Honda fourstroke 15hp and its the cats meow for a small motor.

If I had a line on a good used Yamaha 15 for $500 I`d jump right on it.

 

[robert graham]

Re: 2 stroke 4 stroke ?s

Most modern outboards are quieter than say, Grandpa's Johnson Seahorse 10HP with the cast aluminum cowling back there vibrating! My 90HP 2 stroke Yamaha seems to make about the same decibels at normal running RPM's as my son's 115HP 4 stroke, but at idle or low RPM's the 4 strokes are noticeably quieter! If your buddy's 15HP 2 stroke motor is in good running condition, then you better jump on that one...I think you'd love it! Good Luck!

 

[Sea Rider]

Re: 2 stroke 4 stroke ?s

To take the best out of that future Yam 15 HP, place an induction tach, go full throttle with minimum loaded weight on that jon, check tech specs for min and max rpm parameters for that engine at wot (wide open thottle) if in middle reading, you will be ok. Or try a less pitch prop that gives same middle rpm if near minimum at wot.

Happy Boating

 

[steelespike]

Re: 2 stroke 4 stroke ?s

4 strokes are good motors but usually heavy and have many,many moving parts.
A 2 stroke has more lowend power an has 5 moving parts.
All modern outboards the power head is isolated from the chassis and steering
tiller. I have a feeling your old timer prrobably has lost it isolation dampers
And perhaps the intake silencer is gone.
The only thing that would keep me away from the Yamaha would be if the nearest servicing dealer was a couple of hours drive awauy.

 

[Silvertip]

Re: 2 stroke 4 stroke ?s

Since your area of interest seems to be Yamaha, go to their web site and look at PERFORMANCE BULLETINS. Pick the technology (2 or 4-stroke), HP range, boat manufacturer and boat type and look at the test reports. They not only list fuel consumption at various speeds and rpm, but they also list noise levels at those speeds. When you compare two stroke noise levels to comparable 4-stroke engines you will find that at wide open throttle there is really very little difference. I also find it odd that lately some of the noise levels are no longer showing up in those tests. Gee -- I wonder why? You will also see that in some cases the two strokes actually have better fuel economy numbers (not by much) but there are instances where that happens. Lastly, when comparing fuel economy, make sure you compare those numbers at SPEED, not rpm. The reason for that is that four strokes fire on every other round of the crankshaft whereas a two stroke fires every round. That also means the two stroke is almost always pushing the boat faster than a four stroke at the same rpm so. Therefore comparing economy at the same rpm is skewed. The four stroke will always show better but it is also pushing the boat slower.

 

[settnhooks]

Re: 2 stroke 4 stroke ?s

Tons of great info, thanks everyone. The pros of the 2 stroke are outweighing the 4, and I've got a possible good deal in the making. and I might be able to keep my 75 rude, win win. I'll post some pics of Jon and new motor when I get it.
Thanks again for all the input, great site!

 

[cyclops2]

Re: 2 stroke 4 stroke ?s

Something to remember.

My 9.9 Evinrude has a LOUD resonance sound at about 1/4 throttle. Worse than WOT !!

A 15 hp pushing your boat at the same speeds WILL BE QUITER. Less of a load on the engine. Mileage will be better.
You could play with props as mentioned, to keep the WOT in the correct range.