Blow out

[hallett19]

I have a 1970 16.5 Hondo with a 1986 Merc 115 on a land and sea jack plate. Motor is mounted on the last holes and jack plate all the way up. I am trying differnt props from a 14x20 chopper to a 14x24 small ear chopper. Prop shaft is pretty even with the bottom, my tach is 6 grand tach and with the 20 chopper on it the 115 puts the tach well past the 6 grand mark. The 24 runs about 58, 5900 and at times hits 6 grand I'm getting mid 60's on the gps but on occasion the boat takes a hard turn to the left. I'm guessing this is blow out. Will a blow out ring fix this? if so will a blow out ring for 2.0 fit the 115 ? I have to drop the jack plate a bit to help eliminate this. This boat is used for short coarse circle racing so I want to get all i can out of it. Any help would be great.

Thanks

Tim

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[Capt.Insane-o]

Does the motor have a bad crab angle at speed? i.e. motor is not straight. If this is so try a torque tab on the skeg.

[hallett19]

It may have some positive trim not much. I'm trying to keep the prop shaft straight as possible. When it make s that wicked turn all you can do is get out of the throttle, its like theres no steering.

[Mr. Demeanor]

Make a note of your steering wheel position in a straight line at a slow speed (maybe 30mph) and then see where it is at at 60mph. That will tell you how bad your crabbing the engine at speed. If you have cable steering you can just get the engine straight and mark the top of the steering wheel with a peice of tape. If the engine is crabbing it will blow out at slower speeds. Do you have a torque tamer on the skeg?

[hallett19]

No torq tamer on the skeg. I'm running hydraulic steering.

[patchesII]

The torque tab is there to counteract the natural crabbing angle of the case running through the water. All the hydraulic steering is doing is giving you the "leverage" to overcome what the motor is trying to tell you. You still need a torque tab on it