C-28 prop

[Martin610]

Hi Guys,

I think its time to get my propeller off the boat and have it scanned. No damage that I can see but it's never been off the boat and my top end is a little low. I'm turning 3300 max, might be a little under spec.

I don't have a prop puller or the expertise so I going to get some help. I do have a shop that can scan it for me and make adjustments if it needs any.

The only spec I could find for the prop is "19x20" Acme 304. Of course its a 4 blade. Is that the correct specification for a 2013 C-28 with Volvo D4-260?

Any updates to the prop specs since the boat was built that I should know of?

Any help is appreciated.

-martin

 

[Automaticman865]

Martin,
Have a 2012 Cw-28 and was unable to get the engine rpms up to 3500. Original prop was a 19 x 23 and was getting 3300 rpms. We changed out the prop to 19 x 21 and now all is good. Beginning of the season I am able to hit 3600 and at the end of the season usually get to 3500 or in worse case 3450. Also on the east coast just north of Boston. Some years the bottom growth is horrendous and other years its close to nothing. It doesnt take much to slow down the boat.

Stuart

 

[BB marine]

The only spec I could find for the prop is "19x20" Acme 304. Of course its a 4 blade. Is that the correct specification for a 2013 C-28 with Volvo D4-260?

I'm surprised at the propeller spec. and the performance numbers. It seems that the prop you are running should give you higher rpm. The C28 owners that I have talked to were or are still running ( 19 x 23 no cup 1.50 # 2318). This prop in my opinion causes over propping as soon as you fuel up and add equipment. Most owners did not see 3400 rpm which is the minimum max recommended rpm for the D4 260.( 3500 +150/-100). The prop that seems to be the right fit ( 19 X 21 no cup 1.5) This is the opinion's of C28 owners that changed to this prop are seeing the performance Stuart is experiencing.

The question to ask is... how clean was the bottom when you were only getting 3300 rpm? What equipment do you have on board? Dingy ,outboard and extra gear, how many people do you normally cruise with onboard. The difference in performance numbers (RPM and WOT performance) Changes quite a bit with additional load with a non-planing hull that operates at planing speeds.

If the bottom was dirty and you are using the rpm numbers based on that. I would not change prop sizing. If the numbers are with a clean bottom and the boat is equipped with gear and passengers the way you normally boat. Then having the prop tuned to your boating needs would be the right move.

The prop shop that is going to have scan and adjust your prop would be the best source to advise. Another source is the ACME propellers.

 

[Martin610]

Hi Stuart, Hi Brian,

Thanks for the comeback. I am not sure I have a 19x20 on my boat, I was looking to see what normally comes with the boat.

I was getting 3300 at the end of the season with just me on board, no dingy, close to full tank of fuel. I think I have 85 gallons on board.

Bottom did have some growth, the prop itself had barnacles on it. Bad year for growth here in NJ.

Since I'm trying to get it off and have it scanned, just want to make sure I'm propped correctly in the first place. To Brian's and Stuart's point, I may not have the right prop currently. Glad to have that input, thank you.

Looking at the ACME web site, I don't see a listing for a 19x21 with 0 cup. I may have missed it.

Stuart, there are two props that are spec'd close to what you have. The ACME 2778 with .015 cup, and the ACME 892 with .075 cup. Do you remember which one worked for you?

Thanks.

 

[mferguson]

This is what I have on my 2018:

Prop: ACME #2318, 19.0 x 23.0, 4 blade, RH, no cup.

Still get 3480 - 3500R WOT with it - but in fresh water, and a painted but clean hull.

Mike

 

[Martin610]

Thanks Mike, that helps me. I'm not that far off the mark, especially since my hull was far from clean. I might be OK where I am.

 

[Automaticman865]

My boat also came with the ACME #2318 and if you pull the prop it will info stamped on the hub.
Looking at the info I had written I believe the prop is a 19x21 1.50 shaft .045 which is closet to the ACME #1906 yet there is also something about modifying the cup removing .030 to end up as .015 cup.
Btw this was around 6 years ago and the prop and speed has remained constant over the years.

Stuart

 

[Martin610]

Updating an older post. Finally got the old propeller off. It was a bear for my mechanic to deal with. Turns out the keyway was bent and it fought him the whole way. Either myself or the PO must have touched bottom at some point. You couldn't tell by looking at the prop.

I gave the mechanic a nice tip, I liked how he approached the job. He didn't want to use much heat, didn't want to use an impact wrench. Took care not to damage anything.

Now that its off I could read the markings, it's marked 19x23.

The prop shop that I took it to (which is owned by an experienced guy) didn't seem to think I needed to change anything if I was getting 3300 RPM close to full fuel tank with plenty of barnacles.

-martin

 

[BB marine]

A couple of thoughts. (1) The prop key would not bend from an impact. The key would bend if the prop was not installed properly. I have seen props damaged and shafts bent and the key is straight as an arrow. The key must be fitted properly when the prop is installed on the shaft. The first mistake most technicians do when installing a prop is put the key in the key way, slide the prop on to the shaft and tighten it. The technician has no idea if the key is fit properly in the keyway on the shaft and the prop. The proper way of fitting the key, confirm it fits snug in the key way in the shaft and then confirm a proper fit in the prop hub. Next, remove the key, clean the shaft taper and confirm that the taper is clean and there are no high spots, inspect the prop hub bore, clean and no high spots. Now fit the prop on to the shaft taper and by hand push the prop on to the taper. Use a marker and mark the shaft where the prop hub landed on the shaft. This is the draw mark. Remove the prop, install the key in the shaft key way. Now slide the prop onto the shaft push it onto the taper. The prop hub should be in the same location has it was when you checked the draw without the key. Now tighten the prop nut. When properly tightened the prop hub should advance over the line that you made on the shaft. Tightening the nut will advance the hub on the taper. It doesn't need to advance much (.020.) + If the prop is installed correctly the key will not bend.

(2) Your original post was you were not able to get 3300 rpm WOT. You posted that in January. When you launched the boat I would assume that you had a clean bottom. The D4 is rated at 3500 rpm 260 hp. iI properly propped it should turn 3650 WOT full fuel, full water, normal gear on board, average passenger load, clean bottom and calm seas. The reason to prop the engine this way, when there is growth on the hull in the middle of the season or you load extra gear or passengers on board the engine will still operate in spec. The Volvo spec for the D4 is 3500 + 150 rpm - 100. If properly propped there is 250 rpm to accommodate extra loads, disturbed waters, and a dirty bottom.

 

[armor]

Before you mess with the prop, try playing with the trim tabs while at wide open throttle. I’ve found that on mine I can only hit 3500 RPM with the tabs about 0-25% extended. Too much bow down tab and I can’t get up to full rpm and speed at wide open, but it is happy running with full tab extension at 3200 rpm.

 

[S@LTD]

Thanks Martin for starting this discussion. I too can get 3600 RPM with full water tank and yacht ready for a trip as long as there is no more than 50 gallons of fuel. I have a clean bottom with no bottom paint. Always wondered if I was alone getting only 3300 when we have a full tank which is where we keep it most of the time.

To my knowledge we have never hit anything so sounds like I may want to consider dropping to a 19x21 when we do our drive shaft alignment.

 

[Martin610]

Brian and everyone, thanks for the responses.

Just to clarify, my original post was in January, but the test run was done in November of the previous year. Bottom and prop were both very dirty. I had the trim tabs all the way down. Didn't think to try with less tab angle.

My mechanic thought the prop had hit bottom. But to Brian's point, the key is captured (and supported) on both sides by the shaft and prop. Doesn't make sense that prop would look fine and the key bent from an impact.

I was going to reinstall it myself. Brian, thanks for the detailed procedure, very helpful.

My mechanic said I should use nickel anti seize on the parts when I re-install. Does that sound right? He also said the torque value is 50 foot pounds.

Never having done this before, I can use all the help I can get. And I do appreciate it.

-martin

 

[BB marine]

I have never used Anti-size products on underwater hardware. I don't know if it is an old wise tale or truth to stay way from anti-size on under water components. Reason, the metal in the formula. Right or wrong I don't use it. I use a thin layer of a quality marine grease. I was a Mercury Marine service technician for years so I have always used Quicksilver products. There are plenty of good marine grease to choose from. Just apply a thin layer to the shaft taper and prop hub. I do apply grease to the shaft threads.

As far as the proper torque for tightening the prop nut. I have never seen a torque. 50 lbs is probably ok. That should be enough to hold the prop on to the taper and to stop the prop from coming loose when in reverse. That said, I have always been more aggressive. I tighten the prop nut to 100 lbs. If it lands where the cotter pin hole lines up that is tight enough. If not I move the nut clockwise (tighten until the holes line up. The rule of thumb is tighten the nut as tight as you can with a hand wrench. I like consistency so I use the torque wrench. Surprisingly when I remove the nut after a season of cruising the nut is not that tight. It is still snug but not nearly 100 lbs of torque is needed to remove it. The prop actually advances slightly on the taper. The key is having good clean fit prop to shaft and properly installed key in the keyway's.

I pull the prop off the shaft for inspection of the shaft, shaft taper, prop and nut yearly. If done on an annual basis it is a five minute job to remove and 15 minutes to install. In the event that I do damage a prop while cruising I know that the removal of the damaged prop and installation of my spare prop can easily be done in the water. I have an extra key that stays with the spare prop and have fitted it to the shaft in the event I need to do this in the water. Knock on wood!! I have never used my spares for emergency.

When I owned my Cutwater C26 I had one prop that was for normal cruising ( original 17 X17 .105 cup ) and one that I had reduced the cup ( cup reduced to .075). I then put the original cup back into the blades and removed 1" of pitch (17 X16 105 cup). When we were loaded for cruising I could use the 17 X16 and still turn recommended above 4000 rpm 18.5 kts. When not cruising and extended cruising equipment removed the 17 X17 1.05 would work great 4130 rpm 20.5 kts I just sold that prop after selling my Cutwater. I'm am now looking for a pair of 18 X 23 four blade props to use has (boat loaded) spares for my Mainship 34 Pilot. I'm running 18 X 25 now 4LHA STP 240 hp Yanmar rated @ 3300 WOT but recommended to turn 3450 rpm WOT. I'm turnin 3400 rpm now but when we are loaded for cruising full water 80 Gallons and full Fuel 250 gallons and all extra gear on board I know I will be over propped. The small displacement high Hp diesel engines like to run hard but need to be propped correctly to maintain longevity. I consider the 4LHA Yanmar comparable to the D4 Volvo Penta both designed for marine use.

 

[mikey]

wanted to buy: for a 2014 c28 cutwater a 19X 21 no cup 1.5,4 blade,,bronze RH prop,nut,key,anode, in Vancouver BC

 

[mikey]

grease on the shaft threads Brian? I would think locktite holding the prop nut to the shaft would be better. The main function and concern of the prop nut and cotter pin is to fix the prop to the shaft ,removing the nut is a secondary concern.

 

[mikey]

I had to remove the prop from a c28 after tightening it on with about 100 ft lbs. after running the boat for 2 days the prop nut was not all that tight, nor was the prop difficult to remove. I'm thinking after a prop and nut is tightened to 100 ft lbs of torque, run the boat for a few days then retighten to that 100 ft lbs.

 

[BB marine]

grease on the shaft threads Brian? I would think locktite holding the prop nut to the shaft would be better. The main function and concern of the prop nut and cotter pin is to fix the prop to the shaft ,removing the nut is a secondary concern.

Not really. If a cotter pin Stainless steel of proper size is installed the nut will never come of. The nut is used to advance the prop hub onto the prop shaft taper. Normally 100 ft pounds torque will give the proper standoff (advancement onto the taper). If the shaft taper is clean and the prop hub taper is clean (No nicks, gouges, high spots) and the key fit is not causing any type of interference. The prop should be locked on to the shaft after tightening the nut. Yes it may advance .0005 to .001 inch when power is applied, which may take some stretch out of the shaft threads but the nut should still be secure. Between the cotter pin and a snug nut there should never be an issue of the nut becoming loose.

I had to remove the prop from a c28 after tightening it on with about 100 ft lbs. after running the boat for 2 days the prop nut was not all that tight, nor was the prop difficult to remove. I'm thinking after a prop and nut is tightened to 100 ft lbs of torque, run the boat for a few days then retighten to that 100 ft lbs.

My gut tells me that you most likely did not have a good fit when you installed the prop. Fit the prop to the shaft first with out the key. Make sure you have a good fit. Mark the shaft at full hub advancement. The prop should be snug and hard to pull of the taper with using your hands. Now install the key. The prop hub should land in the same location. If it does not the key is causing an interference. If there is key interference and you tighten the nut the standoff advancement is not right. The results is a loose prop that is not properly seated on the shaft and a loose nut. I have seen boat owners and some inexperienced technicians install props that have become loose and actually rattling on the shaft causing a vibration.
If properly installed it is a one and done process.

If you feel comfortable putting loctite on your shaft threads there is nothing wrong with that. For me I use grease. I have never had an issue with a nut falling off a shaft that I installed or a prop coming loose. I have had issues with removing nuts off shafts after they have been on for a number of years. The grease I believe helps.

 

[S. Todd]

I have been using Marine grease (typically Mercruiser 101) on my prop shafts and prop nuts since 1983 and like Brian have never had a negative issue doing so. The props are definitely easier to remove than when ungreased.

 

[mikey]

thanks for your detailed info Brian, always helpful

 

[piglet 2013]

Took Piglet (C28 2013 ) out today after fresh bottom paint, prop speed applied and lengthened trim tabs by 3". I had 65 gal of fuel aboard and no water 2 people aboard. Calm on the Pamlico sound today Trimmed out at 3550 rpm ran 30mph. Best I could do before bottom and trim tab extension was 24mph.3450 rpm. I had the drop fins installed previously but felt they were not enough, adding the 3" was easy and way worth the effort. Spring is here, time to get off the forums and go boating!!!