Mid matched drive train components.

[mwph]

"MIS" matched

I came across a boat in my marina that has been repowered. The 8.1 Horizons were not even offered as an original option in the 98 330 DA. I, for the sake of this question, am assuming that the original transmissions and props remain.

So my question(s)...
Are these transmissions going to perform & hold up to the increased horsepower?
Do the same transmissions go into a boat regardless of the engines option chosen (5.7s or 7.4s)?
Shouldnt the props be adjusted to accommodate the engines?
The hull was never intended to hold these engines, are the differences that big of a deal?

I just found the repower choice & any potential ramifications interesting so any opinions or comments are welcomed.

 

[fwebster]

This is a common occurrence during a 7.4L repower since those engines are no longer produced. There isn't enough power difference to require a different drive ratio, but repitched props would likely be necessary.

However, on earlier boats with older transmissions that are not reversable (or have A & B shift lever positions) and have counter-rotating engines, it is normal to find them with new ZF transmissions that might or might now have the same ratio. In fact, my old 390EC was repowered with new EFI 8.1's by its new owner. He chose to replace both transmissions at the same time and went to new 4 bladed props. I ran the boat shortly after the repower and Wow! what a difference. He spent a chunk of money (thanks to an idiot mechanic he used to inspect risers - filled both engines with seawater by using the wrong gaskets), but it made the old girl a completely different boat.