Should I change props on my 28?

[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.

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?

Didn't change the waterline. Here are some photos heading out for the Veterans Appreciation Tournament at Spring Point Marina in Maine last summer loaded down heavy. Then a couple from this winter with the current configuration. The winter photos have all me and my wife's belongings to live aboard for a couple months as well as all the tackle needed down there.

Will report back in a couple weeks once I get her splashed with the tweaked prop.

[Norseman]

Looks good, but no Bimini top for living aboard a couple of months?

[Jaredh]

Looks good, but no Bimini top for living aboard a couple of months?

Nope, no Bimini top for Isla. We do too much fishing on the boat to have the supports or top in the way. With just two of us on board the hardtop provides plenty of shade.

[Norseman]

Looks good, but no Bimini top for living aboard a couple of months?

Nope, no Bimini top for Isla. We do too much fishing on the boat to have the supports or top in the way. With just two of us on board the hardtop provides plenty of shade.

Wow, you guys are busy: No fishing on my boat, it would take away time and energy from me lounging under the Bimini top with a cold beer and a good book.

[hatchetjoe]

Now what should I do???

I had the restored 19x19 prop with a 4 cup put on my boat today. The boat moves significantly faster now at lower RPMs. At 3200 RPM I now get 15.1 kts instead of 11.5 kts, however WOT dropped from 3800 RPM to only 3600 RPM with a gain of only 1 kt from 17 to 18 kts. So it looks like I have gained higher thrust at lower RPM's but I'm over propped.

I did verify that the prop that I took off today was a 4 blade 17.5x17" prop. With the 19x19 the boat runs well, no excess vibration or other problems.

However, since WOT on the Yanmar is supposed to be 3900 to 4000, getting only 3600 is a problem. The question is what to try next? Depending on the hull type I put into the prop calculator on BoatDiesel I get recommendation for a 19" prop with a pitch of 14.1 or 16.7 which is quite a bit lower than the 17" or 18" pitch on 19" props that some of you have recommended above.

How much should I lower the pitch to get a little over 3900 RPMs at WOT if I stay with the 19" prop?

Thanks!

[rcwhite]

In theory 1in of pitch should get you 1-200 Rpm. Talk to your prop shop, they can assist.

There are other things that can impact the engine output that should be checked before going too far with the prop though. Ex throttle cable adjustment, air intake, aftercooler, fuel flow/filters etc.

[hatchetjoe]

Success! I got the new prop on a couple of days ago. It is a Michigan 4-blade DQX, 19 inch with 17 inch pitch and 5 cup. I haven't had good seas to carefully test the change but it looks like I gained about a 25% increase in speed. With full fuel and water it looks like WOT is back to 3900 rpm and 20 kts instead of 17. More importantly my speed at 3,000 rpm increased from 9.5 to 12.4 kts and at 3,200 we went from 11.5 to 14.5 kts. It's hard to describe but the boat also feels like it is moving easier in the water. I'll still have to find a time with less chop and see what it really does with more carefully obtained numbers.

The one down side is that previously I have never had any problem with my depth sounder losing bottom even up to WOT but now it will occasionally lose bottom while we are at 3,200 rpm. If I bring it back to 3,000 RPM it will regain bottom and seems to be very steady. While they were changing the prop I used a soft rag to clean the face of the transducer and the surrounding mounting rim. Maybe it will work better with a coating of algae?

Thanks for everyone advice!

[RobS]

If the ducer is mounted forward try a touch of bow down with the tabs next time you lose bottom, you may get it back

[Norseman]

. More importantly my speed at 3,000 rpm increased from 9.5 to 12.4 kts and at 3,200 we went from 11.5 to 14.5 kts. It's hard to describe but the boat also feels like it is moving easier in the water.

Curious as to what your speed and fuel burn at max cruise RPM is with the new prop? (3600 RPM)

[hatchetjoe]

Thanks for the suggestion Rob, I'll try that next time I'm out.

Norseman, I haven't gotten to take it out and carefully run speeds at different RPM's yet. I'll post them when I think they are accurate.

[Dudley]

My 1995 Albin 28TE came with the beast, the PenINsular engine which got to the point it was very difficult to start. The previous owner would start and warm the engine before I came over to test run it. Once I got it the problems were obvious. At WOT it ran about 17MPH. The previous owner liked to run it at 12mph.
After 18 months I changed to a Yanmar 6LPS-STP. At WOT I got 27 knots. And 2 miles per gallon. At 6 knots I got 6 miles per gallon. I took a 1,600 KM trip from Castine, Maine to Sarasota Florida and burned 800 gallons of fuel back when diesel was $2.00 a gallon. We used the same prop that came with the boat and never hanged the prop. The driveshaft was poorly aligned so the dripless shaft seal went out after 50 hours. A stuffing box was installed and had to be tightened frequently. Finally, I found a mechanic who aligned the engine, changed out the drive shaft coupling and reinstalled a new dripless shaft seal. I pump out about .5 gallons from the bilge a week instead of 5 gallons a day.

[hatchetjoe]

Finally had a chance today to try running my Albin at WOT with the new 19x17 prop. The boat had full fuel, full water, two people aboard. We were heading into a mild headwind (10kt). The engine was a full operating temperature because we had already run about 3 hours down the ICW. WOT was just 3800 rpm at 16.0 kt. This was running into a 2.4 kt tidal current (predicted). I know I should have turned around and run the other way to get an average and tried a few runs with different trim tab setting but the admiral wanted to get home. So it looks like WOT at 3800 rpm is about 18.0 to 18.4 kt. The important thing for me is that I don't think this boat is under propped. With less fuel and water I might get a little more speed and perhaps a few more rpm's. On to the next repair!