Advice? 8 hp vs 9.9 Yamaha 4 stroke

[hobopacket]

I retract that. I think the newer 2 strokes can idle for a while. My older ones you have to run up after a bit to clear all the oil off the plugs.

[alansmith]

As the gents said...if you can get a 2 stroke it is a much lighter engine than the piggy 4 strokes....

However...my 2 cents on four strokes. I am in Nazi California where you can't even think about bringing a 2 stroke on Lake Tahoe. Don't even get started on guns in California...smile...

Another fact to consider if you are going 4 stroke versus 2 stroke. Like the guys mentioned above...many motors are built on the same motor and they change the horsepower with chips and injection settings. So, i just went through this whole array of measurements of the cowling head, weight of unit, features, and cost. I ended up buying the Suzuki versus Honda, Yamaha, Nissan, Tohatsu, Merc....because i wanted a fuel injected system and by pass most of the crap that happens with carbs. I also wanted a high thrust unit which was only offered by Yami and Zook. It came down to Yami and Zook. Then the cost was cheaper with Zook then Yamaha. I got the 9.8, fuel injected, can rinse out motor with a port on the starboard side of engine without doing the earmuff thingy. I actually use this motor on my 28 foot Sharpie so i also got the power hydraulic tilt so that i can pull the prop out of the water when i am sailing. She ain't a light weight thing. I think maybe 110lbs. I started her up a couple of days ago after sitting with stabilized gas sitting in her since August. I have electric start and rope start. Two pulls on the rope (heh, it's winter and i needed the exercise) and she came to life and idled like a purring little kitten. The Yamaha's out here on the west coast can't be bought with combo of electric with rope pull start. I said BS on that stupid idea. Battery gone tits up and you can't start your engine....insane.

[Kashmir cat]

I've used an 8 hp 2-stroke Yamaha and a 9.8 hp 2-stroke Nissan AND a 9.8 hp 4-stroke Nissan on a 9 foot, 88 pound inflatable "sport boat". While an 8hp will plane up me (210 pounds) and my wife (much lighter), it won't plane up me and my equally obese buddy. Both the 9.8s will plane up me and my buddy, or one fat man, his wife, and 2 dogs. Figure 5 hp per person for planing. Have fun and watch your weight.

[Neziak]

I remember reading about the ability to change propellers with a different pitch to enable easier planing. I can’t find the post anymore so would be interested in the advantages and disadvantages. I have a Yamaha F9.9 with the original propeller.

[a64pilot]

If your bogging down and can’t get onto plane, going to a lower pitch prop will let the motor turn up in RPM and may get you onto plane.
However what you have done is put the engine into a lower gear so to speak, so your going to have to be smart enough not to over rev the thing once your on plane, unless the thing was overpropped to begin with, then your correcting it. Factory prop is a best guess for an average boat, they can’t possibly fit one prop that works for everything. Mine was underpropped for instance, it would jump onto plane like a drag Boat, then hit the rev limiter real soon.
Think of driving a car around in second gear, you can now pull the hill, just your limited a slower speed once over the hill.
This is assuming the engine was propped correctly to begin with.
Propping a speed boat is identical to propping a sailboat. At an average load of weight holding the motor wide open should just just allow it to reach its max RPM with the boat on plane if it’s a planing boat.
If it exceeds max RPM, increase pitch, doesn’t, decrease pitch.