cavitation 205-A

[TXMACK]

Have rcently finished a restore on a 1977 Ranger 205-A Have a 20" shaft 140 hp Johnson also a 1977. I get cavitation and engine over revs just at the plane off point. When I do get it to plane off I can reach 66 mph measured by GPS. Checked the prop even replaced it. Still the same. Found that the boat requires a 25" shaft motor. The Johnson I have is rebuilt and runs great. If I cut the transom down at the mounting point and reinforce and reglass it will it cause problems. The splash well is plenty deep enough. I live outside of Dallas and there are no 25" shaft motors to be found Johnson or otherwise.

 

[UncleWillie]

Re: cavitation 205-A

If the Transom requires a 25" shaft and you are running a 20, you're getting Ventilation because the prop is coming out of the water.
You need a Longer Motor or a Shorter Boat.

 

[TXMACK]

Re: cavitation 205-A

If the Transom requires a 25" shaft and you are running a 20, you're getting Ventilation because the prop is coming out of the water.
You need a Longer Motor or a Shorter Boat.

Yes I said cavitation but you are correct ventilation is the proper term. What I am thinking is cutting the transom down 4" and reinforcing I have plenty of area above water and above the splash well. Just trying to decide if this will work.

 

[NYBo]

Re: cavitation 205-A

You would be better off converting your motor to a 25" shaft.

 

[metriccrescentwrench]

Re: cavitation 205-A

Instead of going through all that trouble I'd think maybe a jack plate might help. It would move the engine aft, so water would have more of a chance to come up to meet the engine. Plus you should be able to drop the height a bit.

HOWEVER, I wonder if by installing a shorter engine than what's intended on your hull you'd be having problems with water intrusion into the cowling etc. (hence the suggestions to convert to a 25" engine).

 

[TXMACK]

Re: cavitation 205-A

Have made my move for better or worse. The 205-A has a straight across transom, the splash well is 10" deep. I cut out 4" off the top of the transom. Lowering the motor 4". Still have 21 inches of transom here. 15" above the water line. Reglassed and will paint in the morning put on water Saturday. I will let you know how it turns out. All the work here was done under the direction of Rod at Gunbarrel Marine Best Boatman on Cedar Creek Lake. I have high hopes he has never steered me wrong. My main problem was the availability of a 25" outboard. None available in my area. Would have had to go to the coast to find one.

 

[crabby captain john]

Re: cavitation 205-A

Removing structure that supports and takes the stress of the motor.....

 

[TXMACK]

Re: cavitation 205-A

Well I have made the cut found that the transom is as solid as the day it was made. Not bad for a 36 year old boat. Fiberglassed and repainted the repair. Put the Boat back on the water and it performed like new. No issues with the structure I have plenty of support for the motor and its stress I checked into that before I made the cut. All in All I am happy with the decision and the performance of the boat.

 

[NYBo]

Re: cavitation 205-A

Thanks for the follow-up. However, the story isn't complete without pictures.