Performance Boats Forum banner

1 - 6 of 6 Posts

·
Registered
Joined
·
2,034 Posts
Discussion Starter #1
Hey, Jim... care to jump in the mix on this one???
I have a 1968 Donzi 2+2 18' barrelback v-drive. It has a SBC in it. I assume it had some BB ford or something originally. Anyway, it has trim tabs and the tabs have to be down quite a bit at speed to keep it from porpising. The shaft angle is 9 or 10*. (been a while since I checked) This seems pretty steep. Tops out at 50 ish.
I have not played with prop position. It is getting ripped apart to recore the deck. Now is the time to change shaft angle if it is a good idea.
What do you think?
Wags

It will get a 383, alum intake, and lose a bunch of weight in the process. The current engine has the circulating pump, raw water pump, iron intake, etc. All that crap is going. Cam driven water pump. velvet drive trans in it too.
 

·
Registered
Joined
·
2,034 Posts
Discussion Starter #2
Tech help? Nothing?
How about this... what is the propshaft angle on most daycruisers?
Wags
 

·
Boat Test GURU
Joined
·
516 Posts
Set the strut angle at 7 degrees if you can. You are still going to get some hop at the top end but should be much less. Make sure the bottom does not have a hook anywhere as this adds to the hop.

JW
 

·
Registered
Joined
·
2,034 Posts
Discussion Starter #4
Thanks Jim. I think I can do close to 7.
The v-drive is already pretty low in the hull, Can't go forward with it because of fuel tank location, but I should be able to get close.
Prop is about 1" from bottom of hull, so I can gain a slight amount there.
Thanks
Wags

I will flip it and do the bottom when the deck is off too.
 

·
Registered
Joined
·
369 Posts
My '67 Donzi 18 2+3 V-Drive also has a small block (Ford), though most of the V-Drive Donzis had big block Fords. The big engine options were only offered with V-Drives, as the stern drives of the '60s could not handle the torque.

My boat handles the same way, especially with passengers in the back seat. I don't have trim tabs, but there are times when I wish I did. The porpoising seems to diminish with the application of more throttle, though. Rough water with a full back seat does get to be a bit wearing. I don't really want to add trim tabs to the transom, so I'm actually contemplating installing one of those "fat sack" water bladders in the bow for ballast. It's what the tuna tower wakeboarding skiboats use in their stern to make a huge wake for the wakeboarders to play on. You can find them at Overton's.

Eric
 

·
Registered
Joined
·
369 Posts
Just curious to know what prop you're running. I've had my best results with an O.J. 12x16 3 blade. I'd like to try more pitch but I can't find anything higher than a 16 pitch in a 12" dia. prop.
 
1 - 6 of 6 Posts
Top