1995 Yamaha 175 to 150 four stroke repower

[Osprey]

I am looking at repowering my 20' Grady White with a Yamaha 150 four stroke. Boat currently has a carbed 1995 175. This motor provides good horsepower and cruise speed, but is a real gas hog. Opinions on whether new 150 is enough power for this heavy hull? Will range really be 2.5 times or more what it is now? Wondering what others experiences have been with four stroke repowers.

 

[jrod8v92ti]

Re: 1995 Yamaha 175 to 150 four stroke repower

not enough for what you want <br />the marine shop that i work at tried it on about the same hull, when the 150 first came out. it could do the job but . . .needs more p o w e r<br />off came the 150 and on went the F200 durring our "lets do the run in" fishing trip that <br />afternoon it turned out perfect.<br /> fuel injected-still saving fuel <br />200hp- a proven engine thats already had its changes and proven itself, more power <br /><br />boat sold next day to a customer that was at the ramp.

 

[swist]

Re: 1995 Yamaha 175 to 150 four stroke repower

Don't forget if you do a one-for-one replacement (same horsepower) of a two-stroke with a four-stroke, the throttle required to achieve a given speed is guaranteed to increase since you will be adding significant engine weight, although you may get still get better gas mileage.<br /><br />If you make the change and also reduce horsepower, as you are suggesting, you've taken a kind of double whammy and you may need to give the 150 so much gas for equivalent perormance that you wipe out any mileage gain, and then some.<br /><br />Only if you feel your boat was overpowered to begin with might this move make sense.<br /><br />Four stroke is a great idea but until they get lighter** (it is happening - new Honda BF150 is actually lighter than the old BF130), you need to really think this through....<br /><br />** and cheaper. You can buy a LOT of gas for the price of some of these things, particularly the big ones.

 

[Osprey]

Re: 1995 Yamaha 175 to 150 four stroke repower

I have looked at the 200 4 stroke and first impression is this would be physically are very big engine for a 20.5' boat. The boat is rated for up to 235HP. What type of fuel economy would I likely see with a 200?

 

[plot4]

Re: 1995 Yamaha 175 to 150 four stroke repower

How about the fact that YAMAHA list the weight for the 150 hpdi and the f150 at the same 475 lbs.<br />Also the suggested price for the 4-stroke is less than the hpdi.

 

[Steamboat]

Re: 1995 Yamaha 175 to 150 four stroke repower

From recent discussions about repowering with friends, if you keep the same horsepower and compare to a carb motor, a general rule of thumb will be close to the 2-stroke EFI engines gets 25% better economy, 2-stroke HPDI gets 35 % better and the 4-stroke gets 35% (same as HPDI). If you get a lower horsepower engine, the economy will not be the same for the reasons previously posted.