Should I change props on my 28?

[hatchetjoe]

My 2002 Albin 28 has a Yanmar 6LPA STP rated at 315 hp. From what I can gather from the notebook that came with the boat a previous owner was only able to get about 3750 RPM wide open with a 4 blade 19x19 prop. The cup of the prop was not noted. He documented 17.2 kts at 3200 RPM. The prop was worked on with the goal of increasing the RPMs to 3900 - 4000 when wide open. When this was done speed at 3200 RPMs dropped to 15.3 kts and there was excessive vibration between 2600 and 3400 RPMs. Apparently, the pitch had been decreased to about 18 inches. A couple of years later it looks like the prop had been changed to a 4-blade 17.5x18 prop. The speed with this prop was about 15 kts at 3200 and WOT was 3800 PRM and 20 kts.

I am now getting 11.5 kts at 3200 RPM with WOT of 3900 and 17 kts. (When I purchased the boat, the marine surveyor said that the boat tachometer was within 25-50 RPM of his photo tach on the flywheel.) From reading a lot of the discussions on this site my boat seems 2-3 kts slower than many of the rest of you with this engine. My speeds are with about 80% fuel and 2 adults on board. My boat may be about 200 lbs. heavier because of a NextGen 3.5 generator and an AC unit.

I got a second Michigan propeller with the boat that is marked 19x19. I assume it is the prop that originally came with the boat. It has some slight surface pitting but when I took it to a prop shop they said it was in good condition and that they could bring to class 1 specs.
Should I switch to the reworked 19x19 prop in the hope of gaining a couple of knots at cruising speed or do you think I will be overloading the engine? I should add that my boat never seems to actually climb out of the hole and fully plane but maybe I’m expecting too much for this hull shape.

Thank for your help!

[Norseman]

Looks like the boat were over-propped to start with.
My understanding is that 4000 rpm should be obtainable at wot.
315 HP rating at 3800 and max cruise at 3600.
I get 17 knots at 3600 and 10.5 gph.
20.5 knots at 4050 rpm.
With full fuel and 3 guys plus food/drinks for a week, the boat is sluggish but will plane and needs trim tabs and smooth water to a achieve the 17 knots at cruise. Going solo and half fuel is noticeable different.
I have a spare prop freshly tuned and balanced, will probably try it out soon and look for any differences.
Another item on the to-do list is an EGT/pyro (Exhaust Gas Temperature gauge) which shows how hard the motor is working, have heard recommendations of running 80% of max EGT and accept that as max continues. (Although Yanmar says 3600 RPM)

My engine is the 6LP-STE, rated at 300 hp, output is the same however as the 315 hp on 6LPA-STP, but they are measured at a different temperature hence the 15 hp difference.
Got a bit of smoke now and will try the an injection cleaner called Diesel Kleen, it will also raise the cetane level and perhaps make it run slightly better.

[hatchetjoe]

I agree the Yanmar "Engine speed and Propeller Matching" document says WOT on the 6LPA-STP should be 3950-4050. I don't want to overload the engine but cruising at 12 kts is frustrating. I didn't do any better right after the boat was hauled out and the bottom painted.

[Norseman]

I agree the Yanmar "Engine speed and Propeller Matching" document says WOT on the 6LPA-STP should be 3950-4050. I don't want to overload the engine but cruising at 12 kts is frustrating. I didn't do any better right after the boat was hauled out and the bottom painted.

What speed do you get at max continues 3600? (Max cruise RPM)

[Norseman]

Have you taken a moisture meter to the hull and bottom, just to make sure the hull is not water soaked?

[Tree]

Cupping of the prop is critical on the Albin. I’d suggest you need to look at a 19 x 18.5 (maybe 18) with a 5 cup. I am able to swing a 20.5 x 19.5 x 3 cup with no issue and hit WOT with a cruise of 18-19knots and WOT at 24 knots. I have however gone back to the original 19x19 with five cup as I tend to run heavy with four and full fuel.

[Norseman]

Just checked my spare prop, no cupping but the average pitch is 17.96” rather than 17.785” on the primary prop.
Should drop my WOT rpm by 50 and increase the cruise and top speed by 1/2 knot or so, in other words go from slightly underpropped to right on target.

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[rcwhite]

Our 28 had a 19x18 with a 5 cup. Slightly under propped but how the yanmar should run. The earlier ones ran a 19x19 but this was changed in later years to avoid overloading.

This would be a good starting point.

[rcwhite]

Should have included 4 blade:)

[LISal]

i just purchased serenity 1998 28te with 315 yanmar previous owner spent a lot of time at bowsler a sweezy getting prop tuned every year. I put it on this year and it looked like jewelry. I get 20 knt at 2950 and she hits about 3750 wide open at 26 plus knts i believe. I have only opened her up once and let her run up to max speed. I was in the bay almost flat and tide was slightly against. I need to spend some time on here before truly knowing her numbers I will post the maiden voyage video on youtube and give address. On video you will see i am in chop with tide and wind slightly against running 2880 and 20.5 mph. I think the prop makes all the difference... Max gave me two props and the other one he said is fine and looks mint but wont give me the performance of the tuned prop. I plan to continue to give them the prop every winter to condition as CApt. Max did..

[Tree]

i just purchased serenity 1998 28te with 315 yanmar previous owner spent a lot of time at bowsler a sweezy getting prop tuned every year. I put it on this year and it looked like jewelry. I get 20 knt at 2950 and she hits about 3750 wide open at 26 plus knts i believe. I have only opened her up once and let her run up to max speed. I was in the bay almost flat and tide was slightly against. I need to spend some time on here before truly knowing her numbers I will post the maiden voyage video on youtube and give address. On video you will see i am in chop with tide and wind slightly against running 2880 and 20.5 mph. I think the prop makes all the difference... Max gave me two props and the other one he said is fine and looks mint but wont give me the performance of the tuned prop. I plan to continue to give them the prop every winter to condition as CApt. Max did..

Your transmission is different to the standard set up though - you're running a 1.5:1 gearbox if i recall? Golden Nugget for performance that one!

[Jaredh]

Currently having mine adjusted from 19x19 to 19x17. Slight cupping.

When running light I have seen rated RPM, but not when loaded up for tuna fishing with 3 guys on board.

Have added the following to the boat which had increased weight significantly:
6 Man Solas A raft on the roof
Radar mast with lighting
43 Gal Livewell in cockpit
2x Yeti Roadie 20s with ice
Yeti 165 with ~160lbs ice on swim platform
2nd 26lb danforth with 30ft chain and 600ft rode
Fishbox full of ice
4x 130 outfits and other tuna gear
3 guys with overnight gear
Portable Generator on roof
If the trip goes well, a 250lb - 500lb dressed tuna on deck

I am looking forward to running at rated cruise rather than ~3000rpm when heavy and ~2000rpm with a fish on deck.

[Norseman]

. and she hits about 3750 wide open at 26 plus knts i

Looks like you are over-propped?
Yanmar says it should go 3950-4050 at WOT.

[Norseman]

Currently having mine adjusted from 19x19 to 19x17. Slight cupping.

When running light I have seen rated RPM, but not when loaded up for tuna fishing with 3 guys on board.

Have added the following to the boat which had increased weight significantly:
6 Man Solas A raft on the roof
Radar mast with lighting
43 Gal Livewell in cockpit
2x Yeti Roadie 20s with ice
Yeti 165 with ~160lbs ice on swim platform
2nd 26lb danforth with 30ft chain and 600ft rode


Fishbox full of ice
4x 130 outfits and other tuna gear
3 guys with overnight gear
Portable Generator on roof
If the trip goes well, a 250lb - 500lb dressed tuna on deck



I am looking forward to running at rated cruise rather than ~3000rpm when heavy and ~2000rpm with a fish on deck.

Would love to see pictures of your boat with all that stuff on it.
Did you raise the waterline and if so, by how much?

[PilgrimPaul]

Our 28 had a 19x18 with a 5 cup. Slightly under propped but how the yanmar should run. The earlier ones ran a 19x19 but this was changed in later years to avoid overloading.

This would be a good starting point.

I'm right now going to report to the prop shop as to what pitch I want the prop adjusted to for this season...
2000 TE 28 with Yanmar 300 6LP. Ran last year with three blade 21X20.75 with 2 cup. I thinkIi want to "go back" to factory 4 blade 18 X 18 (adjust to 17) with a 5 cup as I am reading this thread. But, Question: what about fresh water? we run in Lake Erie...Any advice would be appreciated. Thanks!