Yamaha 90 vs Yamaha 115

Great forum! I am looking at building a Glen-l boat and researching power options. It will be a 20 foot cruiser and I guess it should displace approximately 3000 pounds. They say it can handle 175 hp, will plane with 40 hp and that 80 hp will provide adequate performance. I wont be pulling skiers and my main purpose will be cruising. I’m disinterested in hole-shot performance. I am primarily interested in fuel economy on a per mile basis.<br /><br />Any opinions here will be greatly appreciated. It will use one outboard engine. The Yamaha four strokes seem a good choice. I am wondering if the 115 might actually provide better economy than the 90. It has 9.5% more displacement but 28% more power. I guess the slightly higher compression ratio has something to do with that. I just wonder if I can find the best economic cruise speed at a lower power setting with the 115.<br /><br />Or perhaps someone knows of more thrifty engines than Yamaha. Thanks.

Re: Yamaha 90 vs Yamaha 115

Welcome to iboats.<br /><br />I think you'd be satisfied with the 90, but I think you'd like the 115 more. The 90 is carbed which has pros and cons. The 115 is an EFI which performs better under varying conditions. It should also run slightly more efficiently although the increased cubes will eat a tiny bit more gas.

Re: Yamaha 90 vs Yamaha 115

Hi,<br />Is it the CS-20 You plan to build?<br /> http://www.glen-l.com/designs/cruiser/cs20.html <br /><br />What is the recommended speed ranges for this boat? Cruise speed and max recommended speed?<br /><br />My best guess: a 90 hp 4-stroke (or 2-stroke) will work as long as You do not load the boat with to much people and gear. If You plan to often be more people onboard I would personally step up to 115 hp to get on plan easy and while up on plane be able to cruise at reasonably RPM like 4000-4500 RPM and that way keep both noise and fuel consumption down. A 90 hp will have to work harder (more noise and more RPM mean more fuel).<br /><br />I have a Yamaha F115 EFI 4-stroke myself (I have used it two seasons now). I use it with a DC/Bowrider, 19 ft. The fuelconsumption is reasonable at cruising speed regardless if 1-2 persons or 4-5 persons onboard.<br />The Yamaha F90 4-stroke is for 2005 avaliable with EFI (Electronic Fuel Injection).<br />Just visit Yamaha US website If You want to read some basic info about them.<br />The Yamaha F115 came out on the market in 1999 so You should be able to find a second hand at a reasonable price (but I do not think there are that many second hand out there) so You can keep down the cost. A new Yamaha F115 2005 is rather expensive.<br /><br />Photo of my boat and the Yamaha F115:<br />

Re: Yamaha 90 vs Yamaha 115

Thanks for the help Willy and Bo. Bo your boat seems to be designed for the same mission as the CS-20 that I'm looking to build. It's a good comparison. Since you're happy with the Yamaha 115 EFI I'm sure I will be too. This site shows the prospective build project. <br /><br /> http://www.glen-l.com/designs/cruiser/cs20.html