speed od not working

[calvin007]

speed od not working,speed od in dash is not the problem.can anyone tell me how air pressure accumulates from the lower unit to make the speed od work.and there is not a hole in the line.i need to know if i have to disassemable the lower unit to fix the problem.

 

[Bt Doctur]

water enters thru a small hole in the drive or speedo pickup that is transom mounted. Water pressure causes air pressure to built, moving the speedo needle.

 

[calvin007]

thanks doc...the speed od tube runs thur the bell house down into the back part of the upper unit.ther is no pitot mounted on the hull.