Am I overpropped?

[mjfoster1974]

I’m sure this topic has come up many times before but rather than read a million posts I’d rather ask about my specific situation. I’m the proud new owner of a 2005 Sea Ray Sundancer 420 with a pair of 400 hour 6cta 8.3’s with 450hp. I was told that around 280 hours the Starboard engine ate a valve and was repaired by a local Cummins repair facility and Cummins covered some of the repair despite being out of warranty. As i investigated further I learned about a potential over propping situation. I asked the previous/original owner if he had any prop work done before or after the issue and he said no. My question is how do I know if I’m over propped? Can someone there tell me if I share certain data with you? Yesterday was the last cruise of the year for me due to being up north. So I took it to the fuel dock and topped off both tanks. I took it for a cruise and made the following notes for reference. I hope it helps. @ Idle (600 rpm) 5.85 mph 1000 rpm 9.7 mph 1500 rpm 11.8 mph 2000 rpm 20.5 mph 2200 rpm 25 mph 2500 rpm 29.6 mph 2650 rpm 31.2 mph Any insight is greatly appreciated.   Sincerely, Mike Foster

Topic

[Tony Athens]

Get your tachs checked for accuracy.

Do it at the dock, engine warm at a steady state 2500 RPM.. Write it down..

Then check WOT no-load RPM by just “looking at the tach”  for a second or three.. If they are accurate and you are making full mechanical throttle,  you should see right at 2900-2950RPM on the needles. Write it down. 

There are very early 450 diamonds ( 430 BHP /2600 minimum rated RPM) 

 

 

[Steve Lewis]

MF,

I just looked at the pictures.  If those turbos are original then I would say that you are in pretty good shape as it pertains to Over Prop’d.  I have a color scale and yours are on the Vanilla pudding end of the scale.  My 480CE’s are more Butterscotch and have 700+ hours.  The really bad end of the scale looks like chocolate pudding…..

How long do you plan on keeping the boat and what sort of use do you plan on?  If you are a day boater that is not going to put that many hours on then you would be fine to leave it alone in my opinion.  If you are more like me and my wife and plan on cruising mid to long distances and put hundreds or even a thousand or two on the clock then I would advise to dial the props back 1 inch.  How are you measuring RPM accurately?  Do you have a photo/laser tach?  This question also pertains to the coolant temps.  Those analog gauges are not that accurate.  My smartcraft display shows coolant temps as 161F and 167F.  But if I were to use the analog gauges and put a number on the temps, they would be higher than what is on smartcraft display.

170F on these engines is not bad on its own.  You should have 160F thermostats like I do.  We are having our Cylinder Heads replaced with the upgraded heads and since things will be taken apart I am going to order 2 of the SMX raw water pumps that replace the Sherwoods that came from the factory.  I am interested in seeing if that evens the temps out a bit.  We are in the great lakes(Lake Erie) and our fresh water is about 78F at the warmest so I have good cooling water.  I am also having the AC and HX serviced again as they will be off the engine for the head work and we might as well have that done again even though it has only been 2 seasons.  If your water pumps are starting to wear you could see your coolant temps start to creep up over time. If your AC and/or HX are “mucked up” then that could restrict cooling water flow.  You will know immediately in the spring after you have them serviced.  If you are worried about the coolant temps then you could wait to see the results of the AC and HX service and see if your temps come down a bit.  If they don’t then you can evaluated the SMX water pumps for next layup or some time in the future as you monitor coolant temps.

We have had modifications done to our boat with longevity and reliability in mind.  SMX Double/Double fuel filtration, SMX Water pumps, Prop pitch reduction, new heads, EGT gauges, blasting and repainting the hull bottom and a few other things.  We plan on continuing our cruising and I do not want to worry about things.  We wanted a 48 Sundancer but that did not workout so we made the deliberate choice of going with this 460 that is very clean and then put some money into tuning up the mechanicals and such.

That 420 is a nice boat and depending on what your plans are, there are a couple of things that you can do to dial it in.  The Exhaust Gas Temp gauges are a low cost way of monitoring your engines.  Since you do not get fuel burn like I do you can watch your EGT as a correlation to load.  I had the electronics guy install the dials and the wires.  I could not figure out the wire routing from the dash back to the engine compartment.  So I had him do it while he was doing the other electronics wire runs.  I could not get the plugs out of the turbo flange so we had our mechanic do that at the same time he replaced our strbd starter.  I installed the probes and connected the wires.  I credit those EGT gauges with saving my hide one time. 

It reads like you have done your homework so just keep on doing what you are doing and dial it in based on how you are going to use the boat.  Post any questions and the forum will help out.

[mjfoster1974]

Pictures

Thanks for the information. Yes I have the mechanical Diamond Series engines. I purchased the boat this past May and my short list of things to do in this off season are… New Elbows (they’re original) Service aftercoolers and heat exchangers. I know the elbows are originals and manufactured by Dangelo and I couldn’t find any service records on aftercoolers or heat exchanger’s.  The engines run at 170 degrees and I feel that’s a bit high compared to others I know with same engines. As far as the props are concerned do you think I should have them worked to get to the 2730 or is it to small a delta?

[Steve Lewis]

MF,

Sea Ray over prop’s their boats.  It is the degree of over prop that is in question.  Assuming that you have the Diamond 450’s and not the 480CE’s(both were options for that model year) then you are pretty close to being prop’d right.  You are ~100rpm shy.  You are correct that this topic has been answered a million times for others, the concepts are the same and you apply them to your situation.  So I wrote a document consolidating the collective wisdom on Prop tuning.  If you have the Diamond 450’s focus on the “Mechanical Diesel” reference.  If you have the 480CE like I do then you can get fuel burn from Smartcrap display.

On a mechanical diesel, Tony recommends being able to achieve 105% of rated RPM on a full load.  Yours are rated 2600rpm so that means ~2730rpm WOT.  You report 2650rpm

Read the attached to learn all about it and post some pictures of your engine compartment.  That boat came with the “Doomed to Fail” wet exhaust elbows from the factory.  If you are in salt water you will want to have those checked.  If you are in fresh water then the clock is longer but still should be checked.

Familiarize yourself with aftercooler maintenance which is compulsory reading.  Check out Tony’s Tips and do some reading while your boat is on the hard.

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