Carver 3807 prop size

[baker.p@comcast.net]

Hello to the group, I’ve been looking at an 1988 3807. The boat won’t run over about 3000 rpm on both engines. Gas, 454 Mercruiser with 23x25 props. I don’t have an exact comparison but I have seen other boats of similar size and weight running 22x22. Does anyone know what the 3807 came with originally?

[km1125]

Those props do sound a bit large for the boat, but what reduction gears are on the engines?? That'll make a big difference.

I had 22x22 on a 3607 and it used 2.57 gears (and with Crusader 350HP).

[buster53]

I used to have that exact same boat, 1988, also with Merc 454's....wish I could recall what props I had.
FWIW, I now have a 356 with Crusader 8.1's, putting out 385 HP. Smaller, lighter boat with bigger, more powerful engines, meaning I can swing a bigger prop than the 3807 you are looking at. I'm currently turning 22x26.
As mentioned above, until you know what the transmission gear reduction ratio is, you are really just shooting in the dark.
My ratio is 2.52.

[bud37]

Welcome to the forum......sure sounds like over prop......question, how fast is it at idle in the marina fairway. Of course there is fuel, and tuning/timing etc as well to consider.

To be clear are you saying it won't get up on plane and 3000 is max at that point ?

[baker.p@comcast.net]

Bottom is a little dirty, fuel is probably a little old. I didn’t pay attention to the idle speed. REALLY struggled to get up to 15kts at 3000 rpm full throttle. Admittedly the engines need a going through but I expected slightly better performance. I’m thinking someone over propped it attempting to make a trawler. I sure appreciate all the responses. And thank you for the welcome, I’m sure I’ll have a LOT more questions as I dig into this old boat

[buster53]

when you say the bottom is a little dirty, how little is little? FYI, running gear will get way dirtier than the bottom and a lot quicker, meaning a little dirty bottom means a LOT dirtier running gear. It doesn't take a lot of barnacles to greatly reduce speed.
A couple years ago, my boat went back in the water after winter haul out with fresh bottom paint. Whatever the boat yard used on my running gear didn't work. The bottom was nice and clean, but in the short period of 10 weeks, my running gear loaded up enough to cut 8 MPH off my top speed. In 10 weeks, I went from 35 MPH all the way down to 27.
Yes, I agree you are probably overpropped and that needs attention, but more than likely, you have running gear loaded up with barnacles.

[buster53]

Is this boat the one listed for sale in VA?

[MyPleasure]

Hi, when we were figuring out the proper diameter and pitch props for our 36 Uniflite, the boat was way over propped at 19” X 18” 3 blade props, with 350 cu. in. engines.
Top rpm was 3500, and top speed was 18 knots. I wanted the engines to top out at 4200-4400 rpm with full fuel and water. We worked with the local prop shop, and wound up with 16” X 17” 4 blade props. Top rpm was 4400 rpm, and top speed jumped up to 26 knots.
The prop shop told me that every 1” less diameter equals about 200 more rpm, and every inch less pitch increases rpm by roughly 100 rpm.
Hope this helps.