Long Shaft or Short Shaft - The HuntingPA.com Outdoor Community
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post #1 of 16 (permalink) Old 08-08-2011, 09:26 PM Thread Starter
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Long Shaft or Short Shaft

i just got a boat from a friend and it has a 9.9 short shaft chrysler on it. my question is it seems like when i open it up its sucking air or something. its in the water what i think is plenty just wondering if its not past the bottom of the boat enough. from where the motor hooks on i have 20 1/2" to the very bottom of the boat and the motor is 18 1/2 inches to the top of the popeller. is this good or bad seems to me the whole prop should be past the bottom of the boat. i would like to get a bigger motor and want to know what i should look for in the new motor. thanks

"some might call that sky bustin, i call it optimisam"
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post #2 of 16 (permalink) Old 08-08-2011, 11:53 PM
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Re: Long Shaft or Short Shaft

Just my opinion. Short shaft motors are best with transom height to about 17 inches max. 20 inch transom height is a long shaft size.

If you want you COULD cut 4 inches off the transom and reinforce the top of the transom and use your motor. Lots cheaper than getting a long shaft.

Don't know your motor but there are conversion kits available for most motors. You get a 4 inch extension that goes between the lower unit and top shaft housing. also you get new gaskets and longer vertical drive shaft. It takes about 3 hours to convert.
a new motor is not $$$ effective, but an easy solution.

You understanding of the cavitation problem is right on, correct.
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post #3 of 16 (permalink) Old 08-09-2011, 02:36 AM Thread Starter
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Re: Long Shaft or Short Shaft

thats what i thought. i just figured since its just a small 15' fishing boat it would be a short shaft. well it will get me through this year. i plan on going to a 15 18 or 20 can i still disguise a 20 hp to be a 9.9 or is that going overboard a bit. it would be nice to have one that does it all. i wanna fish 10 hp lakes but still want to hit the rivers to. well thanks for the help.

"some might call that sky bustin, i call it optimisam"
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post #4 of 16 (permalink) Old 08-09-2011, 10:13 AM
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Re: Long Shaft or Short Shaft

don't attempt to "disguise" a larger motor for a smaller one. The "vin number has a code which will tell the LEO what HP it really is, and depending on where you intend to use the boat, they are watching that issue real hard. I know of at least six people fined for that at Glendale. Also, check the regs for the lakes you intend to go on. Lots of them have changed the hp limits due to the jet motors needing more hp to get the same propulsion as a lesser hp prop engine.

I gotta go agitate the techies!
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post #5 of 16 (permalink) Old 08-09-2011, 12:13 PM
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Re: Long Shaft or Short Shaft

I could never understand the guys that "disguise" or hop up a fishing boat motor, change decals, etc. If I am out fishing, I want to relax, I want to be out there as long as I can, and I don't care how long it takes to get from one end of the lake to the other. Just my take on the issue !

"Be nice, until its time to not be nice" (Patrick Swayze...Roadhouse)
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post #6 of 16 (permalink) Old 08-09-2011, 01:10 PM
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Re: Long Shaft or Short Shaft

Joe +1
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post #7 of 16 (permalink) Old 08-09-2011, 09:19 PM
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Re: Long Shaft or Short Shaft

my brothers has a bigger carb, 9.9 to a 15. it would have cost more to replace the shot carb with the original 9.9 than it did to buy the 15. of course we didn't fish restricted dams either

if you bought it, a trucker brought it
2F
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post #8 of 16 (permalink) Old 08-10-2011, 12:14 AM
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Re: Long Shaft or Short Shaft

The anti-cavition plate (the flat horizontal plate above the prop) should at the same level as the keel of the boat (or up to a 1/2" or so above it) when the motor is down in the running position. Where does your cavitation plate sit in relation to the lowest point on the hull?
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post #9 of 16 (permalink) Old 08-10-2011, 12:40 AM Thread Starter
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Re: Long Shaft or Short Shaft

joe im with you but if you have ever tryed to go up the mon or ohio with a 9.9 and you would understand. sometimes you need to go a long distance fast so theres more time for fishing. i just want a motor to do it all thats all im looking for. i think its silly to have to change my motor everytime i go out.

"some might call that sky bustin, i call it optimisam"
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post #10 of 16 (permalink) Old 08-10-2011, 01:15 AM
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Re: Long Shaft or Short Shaft

I see your point, you should just tell the wife you need two boats, I can put in a good word for you!

"Be nice, until its time to not be nice" (Patrick Swayze...Roadhouse)
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