prop and heigth 57 big twin 35 electric

[stevenj]

25930 big twin 35 electric.

Iwill try and not ramble, OEM parts manual calls for prop #277617 I currently
have a #304825 ,the best I can read from the back of the prop,the first digit hard to read but pretty sure it is a 3. Is the prop one in the same ?

Next ? is reguarding motor heigth. my anti cav plate is about 2" above the
bottom of the hull, 3 or so if going from the bottom rib.





the transom measures 20 inches, If I have to I will start the search for necessary parts to extend this motor.

I could cut a drop in the transom but would only get maybe 2 inches
which should get the plate to the bottom of the boat. the 5 inch extension
would put the cav plate about 3" below without building up the transom.

This motor is on an 04 mirrocraft 14 footer.










opinions please

thanks Steve

 

[freddyray21]

Re: prop and heigth 57 big twin 35 electric

from the looks of the water line on the boat I think you will be fine where it is at. I had mine down a bit lower and ended up raising it up a bit. As long at it it pumping water you will be fine.

 

[steelespike]

Re: prop and heigth 57 big twin 35 electric

Pretty sure you are going to have ventilation problems and it may not pump water. The water pickup is in the leading edge of the exhaust snout.You could give it a try with a temporary setup.
I think the best solution is an extension.It is normal to run thses old timers a little deeper than newer motors.If necessary you could raise the motor almost an inch without any modification.Netting a 4 inch drop.

 

[samo_ott]

Re: prop and heigth 57 big twin 35 electric

I'm sure you will have problems. I just had the same issue with my '54 big twin. Read this thread.

http://forums.iboats.com/showthread.php?t=264157

That stock engine is built for a 15" transom, not a 20. I'd cut the transom down or lengthen the engine. I had to cut my transom. It helped a lot the 2" and yours looks worse than mine.

And the stock prop should be 10 1/8 x 13 1/4 I believe.

 

[tmcalavy]

Re: prop and heigth 57 big twin 35 electric

I agree on extending the lower, based on your hull design. I found everything necessary to make my stock 57 Big Twin 35hp a long leg on the AOMCI free classifieds, at www.aomci.org
Put a wanted ad in there and wait. You'll need the 5-inch housing extension, longer driveshaft and 5-inch shift shaft connector. I've got a Big Twin and a 57 Johnson FD-11 18hp as twins on my boat. Made both long shafts and now get great traction/bite. Waiting on a clutch dog for the Big Twin and I'll be off to the lake again soon.

 

[samo_ott]

Re: prop and heigth 57 big twin 35 electric

tmcalavy, if you have two old 2 strokers on the back does that mean you have a 4 stroke then?

 

[tashasdaddy]

Re: prop and heigth 57 big twin 35 electric

you have a 17 inch motor for a 15 inch transom. you need the extention.

 

[F_R]

Re: prop and heigth 57 big twin 35 electric

In 1957, boats were made of wood and had keels. Motors were made to run with the A/V plate well under water. They will cavitate and ventilate like crazy if you try to run them high. If you use a straight-edge to extend your boat bottom out to the motor, it should come about half way between the plate and the bulge above it. You can use spacers to jack it up from there till you get to the point of cavitation. As everybody has already told you, you have a short shaft motor on a long shaft transom and it won't work. Extend the motor, don't cut the boat.

 

[stevenj]

Re: prop and heigth 57 big twin 35 electric

Thanks for the replies, according to the concensus I shall start the search for extension parts.

 

[tmcalavy]

Re: prop and heigth 57 big twin 35 electric

Hey samo...don't know: never have run a 4-stroke, but sure do like the sound of the twin 2-strokes. Should be a lot of fun when I get a new clutch dog in the Big Twin. I was surprised how much extra umph the 18hp added with the twin set up. Next project is to get the Texas Maid painted and start working on a 56 Lark 30 I have in the shop. If it pans out, I may try twin Big Twins.

 

[freddyray21]

Re: prop and heigth 57 big twin 35 electric

I am going to respectfully disagree. In looking at the pic the water line is well above the water pump an the cav plate is just a bit above the bottom edge. I would take it out and run it first and see. If it is pumping water and not cavitating then it should be fine.

 

[larky]

Re: prop and heigth 57 big twin 35 electric

I think that water line is from the boat "at rest" not on plane. so on plane it may well be below the water inlet of the outboard.

 

[tmcalavy]

Re: prop and heigth 57 big twin 35 electric

If that hull tapered off to flat at the stern, I'd say he's in the ballpark. But since it tapers to a V and the point of the V is below the cav plate and probably pushing water away...I'd play it safe and put the motor lower somehow.