Long shaft 20" versus 25"

[ronkS2]

Hey guys had one last question on long shafts 20 vs. 25.

I have been very happy with my 20 inch shaft on this boat, but have found a few great deals on a 25 inch shaft.

Anyone have any first hand knowledge good or bad?

Thanks,
Ron

 

[CrispyCringle]

The shaft length should place the prop just below the transom so the prop gets a good flow of water, unblocked by the hull. Too short and it comes out of the water healed over or in waves. But you dont want it too long either. The dimension is measured from the top of the transom clamps on the motor to the cavitation plate on the lower drive. They dont always come out even. So, a 20" may be 23", plus or minus.

 

[Fred]

Not sure what boat you have but I have a 25” (x)long shaft Yamaha on my H26. I would not want anything shorter. On rough water the prop has surfaced on occasion.

 

[JRT]

I don't think I've ever thought "sure wish my prop shaft was shorter".

 

[Will Gilmore]

Keep in mind that the longer the shaft, the more torque the lower unit puts on the motor mount per HP. Sailboats are designed for small aux motors as an after thought. Most of them have minimal transom construction for such support. If you are using something below the 9HP range on a 24'. It shouldn't be an issue. However, if you are over that, you should be sure to reinforce your mount with a plate that spreads the stresses out.
I'm guessing your question stems from some opportunity for a cheap motor just when your 20" shaft motor is looking and acting old. Longer shafts are not better if you don't need them to get your prop in good water.

-Will (Dragonfly)

 

[JRT]

Will, those are great points. In my case I went to 6hp 4 stroke 25" on my O'day 25 and it works better then the old 7.5 hp 2 stroke 20"

Also the new motor is a Sailpro model so it has the high torque lower and prop too.

 

[ronkS2]

I don't think I've ever thought "sure wish my prop shaft was shorter".

Do you know how long your shaft is?

 

[ronkS2]

I have a 24 foot Hunter water ballast.. Sorry just started typing stream of consciousness last night.
Never thought about the added torque with a longer shaft, great input.

 

[JRT]

Do you know how long your shaft is?

Yes, I bought a Tohatsu 6 hp 4 stroke Sailpro 25" extra long motor from https://onlineoutboards.com/ I really wanted the 25" shaft after a season with the old 20" shaft and a couple of rough returns with the prop coming up even with the motor mount all the way down. With the longer shaft I can start it easily in the second drop position which keeps the pull cord at the top of my stern, and then easily drop it all the way down.

I spent a fair amount of time to pick the 6hp sailpro vs a larger heavier 9.8 hp. My new motor is actually about 10 lbs less then my old one, the 3 gallon tank is nicer then the larger old 5 gallon on so that is more weight reduction in the stern. Finally the sailpro has a different prop and lower gearing unit for torque which works much better then my old motor and is way quieter.

I see you are a Hunter 240, that is at least 400 lbs less then my O'Day 25 and the built in stern mount from the ones I've seen is very beefy. I'd get a the same motor I have if I had one like yours. Online Outboards is the cheapest and free shipping, I paid around $1500 ish for mine.

 

[Rick Webb]

I extended the 20" shaft on my 6hp motor to 25" well worth the expense.

Go with the 25"

 

[topcat0399]

I extended the 20" shaft on my 6hp motor to 25" well worth the expense.

Go with the 25"

+1

Wish I had an x-tra long shaft for those times I am caught in short chop...

 

[Crazy Dave Condon]

On s lake 20 inch shaft is fine but at the coast 25 inch due to wave action. One thing to be concerned about tilt the engine up when you launch and retrieve so it will not drag on the ramp

 

[ronkS2]

Hey guys a real clean Tohatsu fell into my lap this week. It is a 9.8 electric start with a 25 inch shaft. After measuring my previous motor and taking some measurements off the hull, optimum outboard for the hull I think is 25 inches as well. If you check my posts, I ran through how I got to my theory, whether it is right or wrong, hell I am not even sure but it is food for thought.
For new motors I found onlineoutboards.com and boats.net to be best online prices. That being said spoke to my local dealers, one who stocks them and sells at cost. The only reason he even buys them is because he has quotas to meet. They make big money on the 200 and ups so chasing a couple hundred on a 9.8 isn't a worry. Another dealer said go to onlineoutboards.com get there price and that is my price as well. Good thing about this is money stays local. Your only consideration there is sales tax.

 

[CrispyCringle]

Im sure the 25" 9.8 will be fine. My only concern with the really long shafts is getting on and off the trailer. Keep an eye out. I got my outboard for online outboards. No problems. Had free shipping and cant remember if they tax or not. But certainly worth a look if local doesnt work out.

 

[Crazy Dave Condon]

Buying on line when motors were brought to me from those who did not do business with me, my policy my customers came first and in case of warranty I made those folks pay first and when reimbursed by the mfg., I returned there monies. I had a few who tried stunts to include two stolen motors

 

[flynhi4u]

We have a 20 inch shaft now but I would love to have a 25 incher. Seems like several times a year we have wave issues and have to deal with our prop cavitating. Annoying as heck. I looked into all the parts I would need to convert shaft lengths but that is the farthest I have gotten. I am sure the next time it cavitates I will be kicking myself.

Sam