Prop scan scheduled for Carver 405

[dsolo]

Based on new owner maintenance recommendations from the forum, I plan on taking props to Holland Propellers, Holland Michigan, for a free scan. A short discussion with one of the techs prompt many questions regarding the boats performance. Below are the questions asked by the tech:

What prop is currently on boat?
I gave him the bill of material description, but I honestly don't know for sure.

What is the WOT rpms?
I indicated the short time I operated the vessel I got up to 4400 rpms

What speed was achieved at WOT?
With wind 32-34 mph

How responsive is handling at idle?
Good with little and no currant, need more toddle with wind and I imagine currant? He seemed to zero in on the boats responsiveness at idle, 800-850 rpms.

Questions went on regarding props closest measurements to hull, strut, and rudder.

He then asked if I know of the new technologies in propeller engineering? My answer was no but I understand things evolve.

So what am I getting into?
What should I expect taking in 20 year old props?
What should I be getting with the above performance questions?

Any help from the group will make me more prepared for the visit. I really don't want to walk out of there with new props if it is not necessary. I also do know enough to make judgement on pitch changes to help at idle.

[dsolo]

That last sentence should read" I do not know enough to determine changes to prop pitch for low RPMs performance.

[tomschauer]

If you are getting 32-34 mph with a 404 and 454 engines, I believe you are doing really well. I would leave the props on the boat and spend the money somewhere else.

[tomschauer]

Sorry, a 405.

[RGrew176]

Source of the post That last sentence should read" I do not know enough to determine changes to prop pitch for low RPMs performance.

Wow, I think that is pretty good performance. I have a 3007 Aft Cabin with twin 270 Crusaders and my top speed is only 25 MPH turning 18" dia 18 pitch props. I would absolutely love to get 34 MPH out of my boat. I really don't think you need to change anything.

[tomschauer]

I can get about 31-32mph out of my 355 on slack tide, cruise is about 23- 25 mph at 3200- 3300 rpm.. The 405 is about 7000# heavier. Before we bought our 355 we were interested in a 405 but one of the reasons we didn't buy it was it was quite a bit slower. Cruise about 19 mph top about 26.

[Lyndon670]

I am stunned that you are getting that speed....into wind no less. Is that speed from a speedometer or GPS. If it is GPS - I'm agree - don't frigging touch those props.....

Just looking at your location, you are in fresh water as well, which makes it even more shocking....you typically loose 3-4kts compared to a similar boat in salt water.

[Carver370]

It is my experience that the prop scan will rarely end up free. There will always be something the props "need" for about $500.

If your props don't show any visible damage, I would leave them be. You aren't going to go any faster and changing the pitch isn't going to do anything drastically to change how the boat idles around the dock. Gas motors are notoriously slow idlers around the dock.

My 1994 370 (the older version of your boat) runs 32-32 mph per gps speed at wide open. Carbed 454 Crusaders as well. I had a free scan done once and they said o was 2" out in pitch. I had them do it and I went from 32-32 mph down to 29 wide open and lost 250 rpm off the top. Brought them back and told them to change it back to how it was and now I'm back to where I need to be.

[dsolo]

WOW, maybe I should leave well enough alone? My speed at WOT was with wind and read from the speedo. Based on what I read here I must question that reading.
At 3200 RPM I get +20 mph, and that reading is GPS.

The props were acid washed at pull-out and are very clean. Detailed inspection could not find any dings, cracks, or shape deformation. I will have to look for the size/pitch markings. I truly do not know what they are. Two previous owners kinda mix things up.

I will save the 240 miles (round trip) and continue with my list of maintenance and discoveries. Boy there are plenty.

Thanks again to all. Your a life line in this project.

PS, I'm having a ball! Love this stuff.

Dan

[Viper]

Do you have any vibration at any speed, or experiencing a feeling while underway that something isn't quite right but you can't put your finger on it like a slight vibration or rumble or whine? I ask this not just because of the props but they are part of an equation and the topic here.

Simply looking at the props will not reveal slight distortions. I can sometimes feel each blade and know when its out even with no signs of impact but have been surprised to find numerous times after a scan that some I thought were okay were indeed off by quite a bit.

The scan will give you visual, on a bar graph spec parameters and whether your props' measurements fall within them. With that in hand, a good prop shop will explain any negative effects and how bad they may be based on the readings, and whether it's something you should be worried about or have addressed/corrected. If you take them in, you should expect that they will need work as is usually the case so you're prepared for the expense. If they are close to spec, thank them for the scan, grab your props, and walk away. I do it all the time but I don't have to go 240 miles! In your case, if no corrections are needed, it's time and money for the drive, and labour to re and re the props if you get the marina to do that for you. If they are way off spec, then you have a decision to make and shouldn't feel pressured into doing anything right there and then, but you'll know it's something you'll have to address eventually. Just don't let them do anything without explaining the effects the fix will have on your performance. If you're happy with the performance, then tell them you want the repairs but don't want anything changed. By going through this process, you can then confidently cross the props off your bucket list.

While the opportunity is available, I would scan them. I use the service quit often. If nothing else, it will give you peace of mind. Whether that peace of mind is worth a 240 mile trip to you is something only you can decide. A scan will also serve to verify that which is stamped on the prop as there's no telling what a previous owner or prop shop did. This information can also be used to compare with the original Carver spec. While you're under the boat, dial the shafts, check shaft alignment through the strut and stern tube, and check the strut bearing.