Originally Posted by tfsilver
I recently purchased a Lagoon 42 TPI cat
. She is a great cat and I am currently retrofitting her. The next job on my list is to repower her. She currently has two 30 HP 3cyl Perkins diesels with shaft drive an fixed props. She currently motors at about 7 knots which is a bit slow for her size. I think that the props are too small.
My plan is to repower her with new 30 HP Yanmars again with shaft drive but now folding props.
I am interested to see if anyone has done this or has any comments.
I switched from fixed props to folding props on my Privilege
37 and speed increased from 5.5kts to 7kts under power at 2200 RPMs. The diameter and pitch
are the critical factors rather than the type (fixed, folding or feathering). I was able to increase diameter and that made a huge difference. Under sail, the folding props have greatly improved performance and I really like design and durability (Flex-o-fold). A good prop vendor should be able to compute the correct diameter and pitch for your boat
based on displacement
, engine HP, and shaft RPM.
Are the Perkins engines worn out? If not, it might be worth your while to experiment
with props before you spend mega bucks on repowering. Even if you do get new engines, the props should still be OK. If your shaft RPM on new engines/transmissions change, however, you may have to change pitch. Flex-o-fold or other vendors may allow you to swap blades for a different pitch if required which is a simple operation.
I have friends with a 37' TPI lagoon
and they seem to like their Perkins diesels just fine and recently repowered one side with another Perkins. Not sure it would be worth the bucks to switch to Yanmars unless the Perkins are really tired.
Happy sailing on your TPI 42. They are great boats.