What length shaft?

HookedOnMarsh · #1 08-07-2009, 10:44 AM

Ok so it looks like I'm going to have to repower this boat soon. Old Mercury has small chip missing around water jacket where head gasket failed and let water in and ate it out.

My motor is a 30" shaft and the bottom of the cavitation plate is currently almost level with the bottom of the boat. I can get my hands on 25" shaft motors easy, but not 30". I was told my cavitation plate should be 3" above the bottom of the boat. If so then a 25" should work OK.

How many of you are running 25" shafts on 80's era Cuddies? Why would my boat have a 30" shaft? I do notice that when I stop I can take off and get on plane without having to fool with the trim much if at all. I also drink a lot of gas. I guess this all points to my motor is too long?

reelapeelin · #2 08-07-2009, 05:29 PM

Quote:

Originally Posted by HookedOnMarsh

Ok so it looks like I'm going to have to repower this boat soon. Old Mercury has small chip missing around water jacket where head gasket failed and let water in and ate it out.

My motor is a 30" shaft and the bottom of the cavitation plate is currently almost level with the bottom of the boat. I can get my hands on 25" shaft motors easy, but not 30". I was told my cavitation plate should be 3" above the bottom of the boat. If so then a 25" should work OK.

How many of you are running 25" shafts on 80's era Cuddies? Why would my boat have a 30" shaft? I do notice that when I stop I can take off and get on plane without having to fool with the trim much if at all. I also drink a lot of gas. I guess this all points to my motor is too long?

Measure straight down from the top of your transom where the motor bracket fits over it, to bottom of the hull under the drain hole...we have no way of knowing if your tranny has been modified to accept a longer shaft or not, but it DOES sound like your present motor is too long...

HookedOnMarsh · #3 08-07-2009, 06:54 PM

Thanks ReelaPeelin. I just measured it and it measured 25" exactly. Why would they have put such a long motor on it for? That would explain my gas mileage and why it seems I can trim up the motor forever without the prop breaking out the water. Well this sure will make finding a replacement motor much easier. Wish it would be easy on my wallet too, but can't get everything I want.

Here's another question. How can I convert this extra long shaft motor back to a long shaft motor? I see a 5" section in between the tailshaft housing and the lower unit. I guess the lower unit driveshaft would also have to be replaced.