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Old 08-16-2016, 12:59 PM   #1
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Pacific Trawler performance

Hi - I am a new member to the forum and new owner of a 2000 Pacific Trawler 40, hull number 35. After 35 years of sailing, my wife and I decided to try a different kind of boating. We recently purchased our boat and even though it's only been a few months, we really love her. There is an issue with our boat, however, that I'd like to get some input from other PT owners in regards to the design and performance of their boat.

During the sea trial the we found that the engine would not achieve the specified RPM's. We have a John Deere 6068, 225 HP that is supposed to reach 2,600 RPM but we were only able to get 2,000 RPM under load. With no load, the engine comes up to 2,750 RPM, which is expected. There was no black exhaust at full throttle, so everyone expected the problem to be fuel related. The engine was also running a bit warmer than normal, close to 200 F. The bottom was freshly painted and clean.

To start with, we had a diesel mechanic look into the over temperature issue. He found the heat exchanger was partially plugged and had a partially collapsed exhaust hose. He felt the collapsed exhaust hose was most likely causing a restriction, which was the reason for the low RPM. The cooling system was cleaned and the exhaust hose replaced. We did another sea trial and the over heating situation was corrected but there was no improvement in the RPM's. Figuring the engine was not getting enough fuel, we changed the fuel filter on the engine and then attached a hose directly to the filter port and into a fresh can of fuel. The thought was to eliminate any possible fuel restrictions in the fuel line before the filter or bad fuel as being a possible cause. There was no improvement in the RPM's. The yard believed, therefore, that it was a prop issue or possibly the weight of the boat. They hauled the boat and verified that the prop was as listed (26 X 24) and the weight as advertised, which was 30,000 pounds loaded (listed at 26,000 empty).

We spoke to a local John Deere dealer and he felt it was most likely a lack of fuel that was causing the low RPM issue. He said that if he could get aboard, he would fix the problem. The boat was in Maine and our local JD mechanic was near where we planned to moor the boat in Massachusetts, so we went ahead with the purchase planning to have them troubleshoot the problem once the boat was home. We did place funds in an escrow account with the broker to be used to fix the RPM issue.

The boat ran fine on the trip down to Massachusetts, running at 1,900 RPM at a speed between 8.5 and 9 knots, which we expected. Once we got the boat home, we had the local JD mechanic aboard. He ran a series of tests along with a sea trial and felt that there was nothing wrong with the engine and that it was performing as would be expected. He brought the wrong fitting to test the pressure of the fuel at the engine filter, so we scheduled another visit. Upon his return, we tested the fuel pressures and did a few other tests and again he felt the engine was fine. His conclusion was that the pitch of the prop was probably incorrect and was causing the low RPM issue.

In the meantime I talked with three different propeller shops to get their thoughts. All three agreed that the 26 X 24 prop was the correct size and pitch for the boat, based on the design specs of the boat. They thought it was probably a lack of fuel that was the cause of the problem. So essentially, the engine guys feel it's a prop problem and the prop guys feel it's a fuel problem.

I figured the next best step, other than fiddling with the prop pitch, was to reach out to other Pacific Trawler owners to learn about the specifics of their boats to see how they compare to our boat. Hopefully, knowing these specs will help us to better understand what might be causing the low RPM's. Please understand that we are not hoping for a 12 knot boat but rather want to make sure the engine is performing as designed and at the correct RPM.

The specs of our boat are as follows:

- Pacific Trawler 40 with the open transom and integral swim platform. We also have the added fuel tank under the platform deck of around 185 gal.

- Weight is 30,000 pounds, fully loaded.

- Engine John Deere 6068, 225 HP, 2,600 RPM.

- Prop is 26" diameter, 24" pitch

- Speed at 2,000 RPM is around 9 knots, which is the maximum speed.

- Floscan reads 3.5 gal/hour at 1,700 RPM at 8 knots. Around 5 gal/hour at 1,900 RPM.

I would appreciate any information other PT owners might have that would help us diagnose this problem.

Thanks and I look forward to hearing from you.

Jim
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Old 08-16-2016, 04:38 PM   #2
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Tengee,

Welcome to the forum, I will bet that you will have your answer in a short while from the very informative and sharing Pacific Trawler owners a couple I have met. In the mean while, you didn't mention the gear ratio of your boat.

As I am one of those who is over propped by design and desire a couple of the comments you make are open to question. If at 2000 RPM,(WOT) out of a 2600 manufacture goal,and no black smoke, the conclusion of this being a fuel issue gains positive thoughts.
Overloading the engine employing a over sized wheel will generally provide. as an expected result, a ton of black smoke.

Now I am not an knowledgeable person on the performance of these boats, so I may be off base. to my knowledge these are operated at a hull speed of around 7-8 knots in the 1600-1700 RPM range. That you are achieving speeds in the excess of 9 knots plus under your current status surprises me though I don't offer and doubt;

Were you to find that due to a different gear ratio over those of the three that run the same size wheel then the over propped issue would be suspect in spite of no black smoke.

In our case over propping allows us to obtain hull speed of 6.5-7 knots at 1350-1400 RPM with still a 500 RPM buffer to WOT . We enjoy this over propping for the quietness of running. We may have a slightly higher fuel burn as a result as it is 1.5 GPH where as others with the same power (4-236 Perkins) same gear ratio but smaller wheel claim 1 GPH running at a higher RPMs but under less strain on the power train.

Will be interesting to follow the conversation.


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Old 08-16-2016, 05:41 PM   #3
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Thanks for your response, Al. After pressing the send button, I remembered that I did not include the gear ratio, which is 2.45:1.

I agree that the lack of black exhaust has added a twist to this puzzle. Every diesel mechanic I've spoken to is surprised when they hear this fact. Besides black exhaust, an overloaded engine's temperature will also rise. This is not happening either. The engine runs consistently between 180 and 185 F. It does not exceed 185 F at WOT, which in this case is 2000 RPM.

I was told to stay away from running near WOT and keep the engine at or below 1800, since the engine is being over-stressed at 2000. I would agree if it were an over-prop situation but is it?

Jim
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Old 08-16-2016, 06:56 PM   #4
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Sounds like a question for boatdiesel.com
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Old 08-16-2016, 09:00 PM   #5
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Any reason why the rpm gauge may be faulty?
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Old 08-17-2016, 02:46 AM   #6
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Air intakes clogged or pump timing?

Engines need all 3 regardless of fuel type... Diesels love fuel to a point..if no black smoke maybe not getting enough fuel/air/timing or in the right ratio?

My Cummins ISB (I know different engine) is a clean burning pussy cat on oem fuel delivery but a beast when overfueled...it also spews black smoke like nobody's business...
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Old 08-17-2016, 04:23 AM   #7
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Governor issues?
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Old 08-17-2016, 05:01 AM   #8
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I agree with the above.

Sounds to me to be certainly an over propped boat.

if your going 2 knots above hull speed, your engine is doing the required work.

The only indication of an engine issue is the lack of black smoke at full power, BUT that to me does not rule out over propping.

But all your mechanics are certainly happy.

I would not worry about it and I still don't like the idea of WOT in other than cases of I need to get the hell out of here NOW
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Old 08-17-2016, 05:48 AM   #9
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Thank you all for your thoughts.

In response, the flybridge and pilothouse tachometers match. The mechanic verified that both were correct with a timing light.

Air filters and turbo were checked. Both determined to be fine.

Timing ratios were also checked as well as the governor.

Another thought came to mind which I thought I'd pass along. Under no load, the RPM steadily increases with the increase in throttle. Under load, the RPM reaches 2000 with 10-15% of the throttle still remaining. The final 10-15% of the throttle movement has no effect on the RPM's.
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Old 08-17-2016, 10:59 AM   #10
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I have an update. Another Pacific Trawler 40 owner, who owns the same boat with the same engine was kind enough to respond to an email inquiry. His boat has a 24 X 22 prop and has achieved the correct engine RPM of 2,600. He also recalls a sea trial speed of 11-12 knots. This information is all good news since I believe it is the missing piece to our puzzle.

I would like to thank all who have responded and would still gladly accept information from other PT owners in regards to their boat's specs.

Jim
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Old 08-17-2016, 01:20 PM   #11
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Quote:
Originally Posted by Tengee View Post
I have an update. Another Pacific Trawler 40 owner, who owns the same boat with the same engine was kind enough to respond to an email inquiry. His boat has a 24 X 22 prop and has achieved the correct engine RPM of 2,600. He also recalls a sea trial speed of 11-12 knots. This information is all good news since I believe it is the missing piece to our puzzle.
I am really in disbelief all these prop shops told you the 26 x 24 was the right prop if indeed a 24 x 22 is the RIGHT prop.
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Old 08-18-2016, 08:19 AM   #12
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It does seem odd. From what I've learned however, determining the correct prop size and pitch is not an exact science. The boat specs are fed into a computer program and the suggested prop specs are spit out. If the wheel does not perform as expected, some experimentation follows. On a boat like ours, a displacement or semi-displacement hull, the shops seem to feel as close to a "square prop" is a good starting point. In other words 26"x 26" or 24"x 24", etc. From there the tweeking begins.

In our case, using the known specs of the boat, a 26"x 24" was determined to be the correct size. Being a semi-custom design however, there are some unknowns. I spoke with the boat builder and he said he recalled (it's been 15 years, so he was going off memory) there was a cavitation issue on some boats and at some point in time, they lowered the prop shaft to give more clearance around the prop. Was this considered in the calculations done by the computer program? Possibly not. One shop said the 26"x 24" was correct but then he said the computer also determined a 26" x 19" was correct. He felt that this couldn't be correct, even though it was specified by the computer.

From what I've read, reducing the prop diameter 1" will increase RPM by 500. Every inch reduction in pitch will increase RPM by 200. This would seem to be an easy way to exactly modify a wheel and eliminate experimentation. However, the shops told me that this is a very, very general rule of thumb and other variables, like prop configuration, boat speed, prop materials, etc. will cause unexpected results.

Why does our boat potentially have the wrong size prop, I don't know. The boat must have performed as designed at the initial sea trials, otherwise the engine manufacturer would not have warranted the engine. Was there a change in diameter and pitch at the request of the previous owner for a reason? Again, I don't know since the boat's history is not available.

When passing along what I've learned about a wheel size that works on another boat with the same specs as ours, the prop shop recommended dropping the diameter by an inch and the pitch by two inches, then see what the results are. If a further reduction is required, then that will be the next step. It's easier to remove material than add it back on. This is the direction we will go...at least for now...
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Old 08-18-2016, 08:41 AM   #13
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Tengee, for future reference, he powerplant section of this forum or even the general section would have got you more action on this thread by more knowledgeable people.

You are definitely overpropped. That should have been your first rabbit hole, not your last. How did your boat get there?? There are numerous reasons. It was likely properly propped when it left the factory. But boats gain weight. They gain it by the crap their owners put on the boat. The gain it by filling all fluids to full. They gain it by the water absorption into the laminate of the hull....yes, all glass boats absorb water.

Is your boat 30,000 pounds on paper or 30,000 pounds as measured by a scale??? I am thinking it is a spec and not actual weight. That spec weight means absolutely NOTHING!!!! You need actual weight for prop calculators. And prop calculators just get you in the general vicinity. They are not exact. You are putting WAY TOO MUCH weight on the prop calculator and ignoring reality. The reality is your boat is likely heavier than the spec weight. And the reality is your engine is not making rated ROM. And the reality is the number one cause for not making rated RPM is having too much prop pitch or diameter.

The lack of black smoke and the lack of increasing COOLANT temperatures mean nothing. Yes, black smoke means the engine is overfueling. But an engine can run for quite awhile being overloaded without black smoke and without heat indications on the coolant gauge. Now if you had an exhaust temperature gauge, THAT is where you would find your increase in temperature. An overloaded engine WILL have hotter EGT readings. And it is that hotter gas temps that indicate hotter cylinder/combustion temps that will cause damage to your engine over time.

A very highly recommend you enroll over at Boatdiesel.com and do some reading. At the very least, go to www.sbmar.com and check out "Tony's Tips". His is Cummins related but a ton of that stuff relates to any diesel.

Check out this article in particular:

http://www.sbmar.com/articles/engine...ngine-loading/
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Old 08-18-2016, 08:51 AM   #14
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Boat was weighed on a scale at 30,000 pounds.
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Old 08-18-2016, 08:58 AM   #15
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Quote:
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Boat was weighed on a scale at 30,000 pounds.
Still...that is just one parameter. Take what I said into account and read that article. You are assuming a lot based on weights and formulas when the reality is staring you in the face. You are overpropeed!!! That article is based on higher output engines running at high loads, but it has a lot of information that still applies here.
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Old 08-18-2016, 09:09 AM   #16
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These are quotes from the article and the point I was trying to make:

<<Concerning this propping issue, let me add this to the subject. Using “EXACT MATH” to figure the correct prop size, does not apply, and even further, will never apply, and at best, will only guide the boat owner, builder, or architect, etc, to a reasonable starting point in his endeavors to get the best performance vs a combination of engine life and all of the other variables that affect vessel operation.>>

<<The “EXACT MATH” that typically comes from prop calculators, graphs, architects, builders, etc. when figuring a prop size is much more likely to lead to “running on the edge” or worse, than yielding the correct prop size to insure good engine life in relation to performance. Nothing can replace “on board” engine monitoring and the understanding of (all) engine operational parameters during normal operation…NOTHING!>>

IOW, prop calculators, et al., are THEORY and the are not REALITY. Deal in REALITY(actual engine indications,etc.) to get to where you need to go. You are getting too hung up on the calculators and what the broker said and what the mechanic said. You will soon become very surprised out how little those people know about YOUR engine and YOUR boat.
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Old 08-18-2016, 10:36 PM   #17
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Hi Mr. Baker,
I did visit and read the article and in the past several similar articles that leave me with frustrations. I am flumxed still after reading this one in conjunction of past forum discussions.

I again will use our boat as the example. Factory weight was advertised at 10,000# Now the first head shaker is each owner purchinging this model was given the responsibility for the options of selecting fuel/water tankage, engine selection and gear ration. So it would appear the factor weight as you indicated,really has little bearing on the final first time into the water weight.

Two boats- Ours was equipped with 100 gallon fuel, 48 gallon water. second boat has 200 gallons fuel and 100 gallons water. Our boat had a 700# Perkins 4-154 and the second a 1300# Perkins 4-236. Our gear was 3:1 and the second was 2:1. each with a different weight.
Obviously ours had a large weight discrepancy when compared to the second boat. (Later here you will read of modifications)


Enter the new owner, (me). It was obvious in the first venture into 3 foot seas and 20 knot wind that this boat was so out of balance stability wise as to make me regret the purchase.
After many conversations including the forum, we added 1000# of lead Note, these boats came with 1500 lead incased keels so that is a set factor.

When we changed the 4-154 out for a 4-236 we also changed from 3:1 to 2:1 gear. Total weight change was a positive 700/750# increase.

The prop on the 4-154 (24x16 3 blade) was mated correctly, the engine turned the required 3000RPM at WOT. the max speed at that setting netted a knot and half over the comfortable setting of 2150 and 6.3-6.5 knots, hull speed by calculation being 6.9 knots. ( turning at 2400 gave the hull speed but also a notable increase in cabin sound as well fuel burn. 1 gallon per hour to 1.5 gallon per hour)


We then made a change from the 4-154 as the main seal on these engines and twice changed at $1500.00 on ours, leak and leak badly.) we chose to replace the engine with a 4-236 which added 600# to the mix.

Now here is the rub reflected somewhat in the discussion. We retained the prop (24x16 three blade) from the 4-154 (3:1 gear) and installed a 2:1 gear retaining this prop. The result was a max WOT of 2000 RPM. obviously over propped.
Take you pick, there are three fractory ratings for this Perkins engine. 2500 RPM for continues heavy duty (what ever that means) 2800 RPM for intermendate duty and 3000 for I guess call it 'Light duty" what ever,
we choose to use the 2500 RPM as it represents 2000 RPM the more aggressive application. So- we are then 500 RPM under that number (over propped). By all measurements, we are so far out of wack as to the 'Norm' and yet, yet,
Mr. Baker, all seems to be in tune. We have since the engine swap and the 1000# of lead ingots, added yet another 400# of ingots. Guess what, we are maintain the 6.5-7 knots at the 13.50-1400 RPM with 500 RPM to spare to WOT. It would seem we should be effecting engine failure. yet again, our operating temp is 160 degrees, I am not sure about the exhaust temp, but guessing by conversation, that our operating temp being as low has some equation to any and all temperature factors.
Our fuel burn is 1.5 gallon per hour.
When we tested at WOT 2000 RPM for a period, we met the original increase of 1.5 knots of the 4-154, lots of black smoke, lots!!! And sound, my God! The noise.
With the 4-236 at 1400 RPM out cabin db's is 71 dbs.

In conclusion, while adhering to recommendations such as the site you offer and admitted factors by formulas being subject to question, the actual results as reported should be worth consideration? Would welcome your input on this submission. Where are the results wrong?

Thanks Mr.Baker.
Al


Not choosing to be argumentative, rather, unable to stand by with real life experience that includes so many of the topic related to what is 'Right' and what is 'Wrong'. the 'Gospel' is so many times open to interpretation I suppose.
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Old 08-19-2016, 12:03 AM   #18
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I am firmly in your camp. I also have a deliberately over-propped boat. This is also due to an change in engines. I went from a pair of Volvo TMD40s rated at 145hp to a pair of TAMD41s rated at 200 hp. I kept the same props, and at the same rpm, gained some fuel efficiency in addition to the extra hp. My cruising speed increased by 1 knot, to 8.2.
My mechanic, a Volvo specialist, who sold me the engines and supervised the installation, recommended over-propping, to gain further fuel efficiency and run quieter. I added 4" of pitch, bringing my cruise rpm from 2700 to 2100. The fuel efficiency gains were about 5%, on top of a 10% gain from the direct injection engines, part of which I gave up to cruise 1kn faster.
These engines are rated to top out at 3600 rpm, so my mechanic says they will last a lot longer now that I am running them slower.
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Old 08-19-2016, 02:34 AM   #19
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Tengee-it seems you have checked just about everything, and the consensus here at least is that you may be overpropped. But you never mentioned whether you actually had the prop checked to make sure it is indeed 26x24? It certainly wouldn't hurt to find an inexpensive 24x22 and give it a try.
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Old 08-19-2016, 07:58 AM   #20
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Agreed. The prop is stamped 26x24 but I won't be able to verify that until the boat is hauled this fall.
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