Pacific Trawler performance

Baker said:

Usually when turbos go bad there is black smoke due to the lack of boost and over fueling. Was that not the case?

Click to expand...

I think because the turbos don't significantly boost the Hp over the NA motors the fuel flow is not that great of difference...

Baker- I got your message and skimmed through this. Lots of words and I admit I have not digested every argument.

Regarding the OP's boat, a few things stand out. Running 9kts at 1900 at 5gph on a 30k 40ft boat is pushing it well past hull speed. With max available hp of 225 that thing is not going to plane or semi plane. Any additional hp beyond 1900 is simply going dig more hole and make more wake.

It looks like it is overpropped. Might be intentional by some PO. No problem running this way, but not too good if you try to push it past say 1700.

You could change the prop to get to 2600 but there really is not any benefit to doing this. Due to the boat, anything above 8kts is a no-go zone and rather pointless to prop for operation there.

Keep the same prop and don't try to cheat hull speed and the engine will be fine.

I have sea trialed many trawlers that are intentionally overpropped. I make a note of it, make sure the buyer understands what it means regarding operation, and that is it. If engine is otherwise healthy, no big deal.

In the op's case, one thing that seems a little off is that with a max of 2000, the flowscan is reading 5gph at 1900. That is about 90hp. I would expect it to be higher than that. And would expect black smoke at 2000.

Might be worth putting a boost gauge on. Boost will be pretty low there, but should be some, maybe 5psi. It won't go to spec if engine can't get to 2600, but it should show some.

If engine is running fine, I would not spend a lot of time and money chasing that last 600rpm. It is not practical to run over 1700, why do battle to get there.

Hi Tengee,

My Pacific Trawler 40, hull #37, is equipped with the John Deere 6076AFM30, specified by John Deere at 300 hp at 2400 RPM. Interesting that they were probably delivered within months of each other, but with different engines from JD??? Although I haven't weighed my boat, I do not doubt it weighs within a few hundred pounds of yours, as mine also includes 65 gal of water and 65 gal of fuel in the swim step.

My transmission is a Twin-Disc, with a ratio of 2:1. Interesting that yours is 2.45:1, which complicates things a bit. In addition, mine is specified at 2400 WOT at no-load, versus your 2600. Some performance results of MY hull, which carries a 25" x 23" five-blade prop, are as follows:

1200 RPM=7.1 knots
1600=9
1800=9.3
2000=10
2200=11
2400=11.8

In my personal opinion, propellor calculators cannot be expected to provide an exact match to hull/engine combinations. They simply get you in the ballpark. Your existing propellor is close, but (again, in my opinion) apears to be over-pitched. As reducing propellor diameter is a one-way street, it would be my suggestion to de-pitch your prop two inches, and try again.

Yes, you can live with an over-pitched prop. Many operators do so, but you run the risk of overfueling the engine at WOT, and having to explain to your next owner (and providing some cash at sale to correct the situation) why the engine will not achieve WOT of 2600 RPM. And yes, anything over about 7.5 knots is in excess of hull speed on our hulls, but so what? For what it's worth, my fuel burn at 1600 RPM is 4.2 gph. That's low enough for me. Still gives my about 800 nm range, not including reserve.

Hope you enjoy your new boat. Mine's a peach.

Regards,

Pete

Thanks for the great reply, Pete. It is the type of response I was hoping for when I originally posted the thread. I did converse via email with another owner named Mike who reported that he owned hull #37. Is yours possibly hull #39?

Anyway, I am strongly leaning toward the prop being over-pitched. Once the boat is hauled this fall, I am going to have the prop inspected to qualify the exact diameter and pitch. Then look to determine the necessary adjustments. I realize the first adjustment may not give the exact results we're looking for but hopefully, we'll be closer to the specified RPM. I do not plan to live with the current situation, since I believe the engine should be run and achieve its designed specifications.

It is interesting that you have a larger engine and a 5-blade prop but are still getting results that are similar to what I believe we should achieve with our boat, with the correct prop that is. I did talk with the builder and he said that they put a few JD's into some of the boats but I didn't know they were different sizes. I guess they were still doing some experimenting with the power packages after adding the integral swim platform and extra tanks.

Our boat has the added fuel tank back aft (165 gal.) giving us a total of 600 gal. There is no water tank. We currently run the engine at 1,700 burning around 3-3.5 gal./hour doing around 8 knots. Gives us a decent range.

Thanks again for your response, Pete. We have really enjoyed our boat so far and look forward to many years of good cruising on her.

Jim

Hi Jim,

Oops, yup, mine's hull #39. And FYI, I have my prop at the Prop Shop as we speak, and have asked them to note the EXACT pitch and diameter on the invoice. The info I previously provided (25" dia x 23" pitch) is marked on the hub, but who knows the actual numbers. Will find out soon, and update accordingly.

Not to hijack your thread, but interesting that you have a 165 gal fuel tank in the swimstep, vs my 65 gal fuel and 65 gal water, for a total of 465 gal of fuel and 265 gal water. My water tank in the swimstep feeds the manual head, which means I don't have to monkey with solenoids and backflow preventers on my ship's water system to provide safe fresh water flushes. In my install, the tanks are separated by about 36", which leaves a 2nd lazarette.

Looks like these boats were far from cookie-cutter boats, as I have yet to see two that are identical. Via the grape vine, it seems like the builder might have been a little TOO generous with buyer-requested mods, which may have contributed to the brand's demise. Too bad. There's some features on the Pacific Trawler that I very much value vs both the Nordic and American Trawler lines. Doubt I could afford a new one if Pacific Trawler were still in business, and glad I've got mine. Enjoy!

Regards,

Pete

Thanks for the response, Pete. Interesting set up for the freshwater feed to the head. Should I ever run into problems with the aft tank and need to make a change, adding a water tank back there that would be exclusively for the head would be a good idea.

Before buying our boat, we looked very seriously at the Nordic and American Tugs. We were on several of them and came close to buying. However, we have actually found many features in the PT40 that we like much better than the other tugs. Granted she has only one stateroom but the extra room gained in the salon, galley and the up head makes her a much better boat for us. Being a more custom boat, I have found that the quality of build is actually equal to or better. Nice to hear you have similar feelings about your boat.

Jim

Hi Jim,

Final numbers on my propellor, as it's back from the Prop Shop. Mine is 25" dia x 23.5" pitch, RH, 5-blade. Hope this info helps.

Regards,

Pete

Hi Pete - Thanks for following up and sending the prop numbers. Very helpful. I will pass these dimensions off to the prop guy for comparison.

Jim

Hearsay marine engineer/architect rule of thumb prop/engine/transmission/hull specification test......No load RPM divided by full throatle loaded RPM over distance should be around ratio of .75. (2750/2000=.727) Close enough. With that result I would be content.

After learning that another boat that is almost identical to ours had a 26x23 prop and was able to reach 2600 RPM's, I decided to revisit the thought that the diesel engine may be the cause of the low PRM's. The engine was again fully checked out with gauges connected to the fuel side and exhaust side with it under no-load and load conditions. The mechanic said the engine was performing "perfectly." We next tried adjusting the high-pressure pump stops under load and the throttle cable as well. Once again, the highest under-load RPM we could achieve was 2200.

The only remaining option was to remove the high-pressure pump to have it cleaned and recalibrated. Once the pump was removed and brought back to the shop, it was found to have a device on it called an aneroid. Basically, an aneroid mechanically controls the fuel levels so the proper fuel/air ratio is maintained during the throttling up process. This aneroid was frozen stuck in a position which did not allow the fuel quantity needed to reach the higher engine RPM's to pass through the pump.

The aneroid was replaced, the pump was cleaned, recalibrated and replaced. At sea trial the engine came up to 2600 RPM and matched the performance ratings for the engine. We put eight hours on the engine over the weekend and it performed as designed. A good learning experience for all involved.

Well done!!! Glad you got it figured out!!! Two years of problem solving!!! Well at least no damage was being done while operating the boat like that. It was simply just not allowing you fuel!

What an interesting result , been reading the entire thread , who knew about 'aneroid' in injector pumps? Apparently nobody! On the forum or mechanics , even the ones that said it was fuel staved. You learn somthing new everyday.
The PT 40's certainly look like interesting trawlers, well built and in the US too.
Is there a thread on the demise of the builder or other details.
Thanks a lot. Warren