Interpreting a propeller balance report

[Bob Waters]

Hello All,
I had my propellers checked, repaired and balanced at Wilmington Propellers in Jan, 2016. The report said the propellers were 2″ off. I’m having a hard time interpreting the report for each prop.

The Propellers are Michigan Hy-Torq, 18X24, 4 blade, #7 cup, 1 3/8 bore. The engines are Yanmar 4LHA-DTE @ 200 HP. The gears are ZF 450 A, 2.0 reduction. The boat is a Henriques 28 Express. The factory Tachs read about 150 high at 3,000 rpm, so tach at 3,000 rpm and photo tach is at 2850.

Fully loaded, the engines go to 3,500 in flat seas. I interpret this to be 3350 rpm with tach error correction. Fully loaded is with 3 people and bait tank full. At light load, eg. bait tank empty and 2 people, the rpm hits 3550 and I think the governors are limiting the rpm. I think the current propeller setup is close. I run the engines at 3,000 (2850 real rpm), when conditions permit and speed is between 20.5 to 21.5 knots at full load. At light load, speed is 22.5 kts.

Mechanically, everything is good with the engines. They have 1550 hours, all service is up to date.

I think I need to take a little out of the propellers. The question is whether to adjust the current props or buy new. I looking at ACME props, but do not know what size to start at. I’m ready to do a haul out and now is the time to make the decision.

Topic

[Bob Waters]

Bill,

The boost hit about 28 when I pegged the throttle and then dropped down to 23 to 25 psi.
I’m used to the boost numbers for the 230/240 STP engine, in which boost was 30+ at WOT and 18/19 at 3,000.

Thanks,
Bob

[Bill Fuller]

A question for Rob or Tony or both.

I am only familiar with the 4LHA-“S” motors. What should the WOT boost be on the “D” motor?
I assumed that it would (probably erroneously) be above 30 psi like the “S” motors.

That along with his boost numbers at 2850 (3,000), which are not bad, is why I thought his numbers seemed a bit off. So, what should Bobs boost be at WOT?

And I agree, a reduction of pitch and probably cup would seem to be in order.

Bill

[Tony Athens]

Bob,

I’ve stayed out of this for a reason———–Rob really is good on stuff like this…………….Learn and listen–He’ll guide you right………………..

Tony

[Bob Waters]

Rob, Yes. You hit it right on the mark.
Thanks

[Rob Schepis]

So you need a true 150rpm bump, I had originally mentioned that same 1″ pitch and cup down from #7 to #5 (reducing effective pitch). That should get you in range..

[Bob Waters]

I got my brother on the boat and did some testing with the following conditions: 80 gallon bait tank full, down 40 gallons of fuel, 2 fat guys, no ice chest. A loaded fishing trip may add 600 pounds of weight with full fuel tanks and one more fat guy.
1- The photo tach verifies that the Aetna tachs are accurate with 3 or 4 rpm of each other.
2- WOT rpm, using the Aetna gauge reveals that Port is 3310 rpm and Star board is 3324nrpm.
3- High Idle is: Port 3737 rpm and Star board is: 3715 rpm.
4- Boost at WOT is Port: 23.5 psi. Star board is: 25
5- Boost at 2850 rpm, which is the 3,000 rpm that I cruise using the Yanmar tach read is, Port 13.5 psi. Star board is 15 psi.

I think I need to take 1″ of pitch off the wheels and go to a #5 cup. Just a guess. Wheels are 18 X 24, #7 cup. Hy Torq brand, reconditioned to ISO 1940 G2.5 tolerences.

What do the others think?

[Bob Waters]

Phil,

I agree that Basin is top notch. Derek is very helpful. It is worth the wait.

Bob

[Philip]

Bob…

There is a reason Basin has a backlog. They aren’t the cheapest but they do it right and stand behind their work. I have always been treated like family there…

Phil

[Bob Waters]

Bill,
I used 127 teeth to set the dip switches.
I have not photo tached the Aetna gauges yet, but I will.
I did check high idle some time ago. I do not remember the value, but I will recheck. Good idea.
I need to get my brother to the boat to help out. My aetna tachs are on the tower.
My haul out is scheduled for July, ugh. Basin Marine is busy. The yard in DP is a rip off. I will not haul out there.

Thank you for the great ideas. I will post when I have more info.

Bob

[Bill Fuller]

Bob,
For some reason the numbers seem a bit “off” to me.
Have you photo tached the Aetna gauges, both engines?
How many teeth did you tell the Aetna tachs to count?
Have you checked the high idle?
Maybe wait for better conditions to get a better set of readings before doing anything.
Let us know.
Bill

[Bob Waters]

Bill,
I installed Aetna Digital Tachometers and Tony’s dual engine boost gauge.
I have attached a spreadsheet of data I collected. The seas were pretty rough during the test. I was on board and 80 gallon bait tank was full. My fully loaded weight will be a little higher than this test.
The Yanmar Tachs were at 3,000. Aetna Tachs read: port- 2786 and Starboard-2820. Boost is:Port 14 psi& Startboard-15 psi.
WOT. Yanmar 1475 for both engines. Aetna: Port 3208. Starboard 3270. Boost: Port 24 psi. Starboard 25 psi.

I’m considering taking 1″ of pitch off each propeller. What do you think?

[Bob Waters]

Hello,
I was at the boat after the rain let up. My camera had a dead battery, so I used my cell phone. I know that is not preferred. I was only able to get clear pictures of the port engine. I will attempt to get the starboard tomorrow with a real camera.

[Bob Waters]

Bill.

I will take some pictures and post them.

Bob

[Bill Fuller]

Bob,
If its not too much trouble, post some pictures, especially the air side of the turbo.
Bill

[Bob Waters]

Hi Bill,

Like you, I love these engines. In fact, I searched for this model year for these engines and the engine room layout. The engine room was built for Volvo 41 series. When Henriques switched to Yanmar 4LHA, they kept the bulk heads in the same place. There is so much room to crawl around the engines, it is very easy to service.
I do not have boost gauges yet. The engines run so well and the fuel economy to great that I did not see a need yet. The exhaust manifold has some discoloration next to the turbo indicating that the engines are producing proper load, I just do not know what actual boost is. The only down side to the boat is a small dash and areas to run wires and hoses for boost gauges.
High idle if I remember is WOT not under load. It is 3,900+. That was with the factory tach. I need to get my brother to the boat and run the photo tach again. I got some numbers but my teen age son was at the throttles and I do not think he was accurate enough with his adjustments.

[Bob Waters]

Hi George, Manny was the sales agent when I purchased the boat 2.5 years ago. He was on board for the survey and there was a question about the propeller size made by the surveyor. The owner quotes 20″ diameter. I found the original size in a binder aboard the boat. Manny then verified that those were correct when it left the factory. It would not hurt to reach out to Manny again. He is a wealth of information.
I agree that every owner is part of the family. I wish I could afford a 35, but I like the fuel economy I get with the 28.

Bob

[Bill Fuller]

Bob,

I know you have been running 4LHAs for a long time so you are well aware of what they should or shouldn’t do.

The way I see the prop scans is that both props are now “balanced”. Anything under the tolerance, 8.3 gem-inch, meets the ISO spec and is balanced. Its just that the first prop is a bit better.

If it were me, I would take an inch out of these props and go forward. Assuming a couple of things, first a couple of questions.

What is you high idle RPM?
Do you have boost gauges?
If so, what is your boost reading when the tach reads 3000 RPM under your normal load conditions?

If your boost at 3000 RPM is around 15-16 psi, I would not change anything. If it is getting up around 20-22+ psi, then you definitely need to reduce pitch.

Anyway, that’s the way I see it.

Let us know what you decide to do, and if possible, answer my three questions.

Bill

[George Forrer]

Are those the original props that came on that boat from new? If not give Henriques a call Manny will tell you what it left the factory with. I have known quiet a few Henriques owners when you buy one of there boats new or used you are like family now. George
Sorry I missed that line where you said you spoke to the factory.

[Bob Waters]

Thanks Rob. I see that the final vibration and overall tolerance are close to identical for each wheel.
The final unbalance are so different. I will call Wilmington.

[Rob Schepis]

Bob,

Keeping each report independent of one another if you look at the initial vs final on the vibration and the unbalance you can see the deltas btwn the befores and afters. Not sure as to comparing LH report to the RH report, best is to speak to them or another prop shop that offers Dynamic Balancing.

[Author]

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