Props

[joeslenzak@gmail.com]

Hi - I'm new to the Carver Forum.
I have a 2002 410 Sport Sedan. The props were changed out at some point by the original owner. It has twin Cummins diesels (370 hp). It struggles to get on plane unless I turn the steering wheel and then it seems break free and come onto plane. Current props are 24x29. I am trying to find out what the original props were on this boat. I think the replacement prop pitch may be too much.

[buster53]

You may be over propped. What is your WOT RPM and what is the engine mfg’s recommended max RPM? We need the answer to those 2 questions before any recommendations can be made.

[bud37]

Welcome to the forum...... to add to the above,....maybe you have but, make sure your trim tabs are working as they should and bottom is not fouled.

[bud37]

One other add....have you got any black smoke from one engine or both ?....see that thing about turning the wheel is interesting. On the sea trial was all ok ?

There are a few things to cross off before the prop consideration.

[KyleR]

We have a 2002 396 with the twin Cummins 6bta 370HP diesels too. I found the original delivery paperwork when we bought our boat and it came standard with 24x29 props. I know it's not the same boat as yours, but very similar and of the same vintage. The delivery paperwork said it hit 3050rpm on the water at delivery.

However, that was for an empty boat with probably not a lot of fuel or water and no personal items. When we bought the boat in 2022 it would only make 2700rpm ar WOT with a clean bottom and none of our "stuff". After two years and fully loaded with a not-so-clean bottom, it only made 2400 rpm at WOT. Obviously WAY overloaded so we basically ran it like a trawler for the last year+ to keep the engine from working so hard.

We just launched today after a month in the yard and now have a very clean bottom and we swapped out the props out for 24×25.5, so we'll see what happens. We're staying on anchor for a few days to chill out and recover but I'll post back once we run it up.

Anyway, long story short, you definitely sound overpropped. Those engines should be able to spin at 3100-3150rpm, under load, at WOT.

Kyle

[joeslenzak@gmail.com]

Thanks Kyle for the info. I don't have the WOT RPM, but I know it will do at least 2800. My typical running speed is 2400 rpm @ approx 19-29 mph. Bottom is clean
Let me know how the new props perform

Joe

[KyleR]

So my first round numbers were 2995rpm on port, 3050rpm on starboard, at WOT. This was with 24x25.5 props, freshly serviced aftercoolers/heat exchangers (per Seaboard method), freshly sanded/painted bottom, 12-15mph cross winds, light chop in the water, in 20-25ft deep water, and the boat weighing in right at 37,000lbs (per the boatyard travel lift scale). I really think on flat water with calm winds I will be able to hit the recommended 3100-3150rpm. This is the best these engines have run since we bought the boat so I'm pretty pleased.

One other thing I noticed was that my throttle levers at the helm were pegged against the dash, so there may have still been additional throttle movement available at the engine if I tweak the cable mounts. I'll be exploring over the next week or so.

[joeslenzak@gmail.com]

Thanks Kyle - Since I don't have WOT rpm data for now I'm going to get the props redone and leave the pitch. I'll test it out in the Summer and gather some data to see where my motors run.

[Chocura370]

You may be over propped. What is your WOT RPM and what is the engine mfg’s recommended max RPM? We need the answer to those 2 questions before any recommendations can be made.

I have same question & situation going on with my ‘93 370 Voyager. I’ve been reading all the post on this topic, and repeatedly see this same question being asked:

“What is your WOT RPM and what is the engine mfg’s recommended max RPM? We need the answer to those 2 questions before any recommendations can be made”

I don’t know how to find the answers, my props are damaged. The engines are original equipment Mercruiser 7.4 gas. How do I know what the max RPM should be? Basically Chevy big block……. I don’t think anything over 3500 rpm continuous would be good for these engines.

Also, most boats at my club all have 3 blade props but min are four blades. Why? What difference does it make?

I pulled the damaged props today. They are roughly 18 inch diameter, shaft size 1-3/8”, stamp on the hub says 18p 21.5. Is there anyone here who will kildy help me figure this out?

[buster53]

Certainly not an expert here:
I believe those engines should max out in the 43-4500 range. No, you don’t run them continuously at that speed, but you do need to open them up from time to time to make sure you are getting full RPM’s
Take your props to a good prop shop. They will fix whatever is wrong and give them back to you looking brand new. They can also give you advice as to what is best for your boat if what you have aren’t the right ones