28' TE - what's the best prop?

[Wish You Were Here]

I have a 2006 28' TE Flush Deck w a Volvo 310. I run a 6 pack charter and my only complaint is that it cruises at 11-12 knots. I've spoken to some other Ablin owners who have same model (but no one had a Volvo) who gets 18~22 knots at cruise. Not sure if this is an engine issue or a prop issue. Wondering if I should get a bigger prop or maybe a different pitch prop? Any thoughts or suggestions?

[hatchetjoe]

Hi Swabby,

I’m a newbie so you can take this with a grain of salt and I’m sure others will chime in.

My opinion is that I also have a “slow” 2002 28 TE. As many people have stated on this forum the 28’s were somewhat individually built so there are noticeable variations between boats. One of those variations is the weight of the boat which directly affects the speed vs power balance. From the scale on the Travellift my boat weighs about 11,400 lbs. Part of that is all the stuff I have on board but also the weight of a genset and AC unit plus nearly full fuel. I also suspect that my hull is heavier than some of the other 28’s because of the layup process the day it was made. I have had the hull examined a couple of times and no one has found any indication of water intrusion that would add to weight.

I’ve written about what I tried to get better boat speed which has included two prop changes ($$$$$).
Here is the link about the props: viewtopic.php?f=5&t=11610&p=76236&hilit ... joe#p76236

I now have fresh bottom paint and Propspeed on the latest prop. The new prop and running with only half tank of fuel has increased my speed at 3200 rpm from 11-12 knots to ~14 knots. I haven’t gotten a good day to try WOT with the changes but I suspect that I will now get 3800+ rpm and 16-18 knots.

My bottom line is that the weight of the boat and the bottom running surface are probably the two biggest influences on boat speed and that tweaking the prop may give you an additional 15-20% if the current prop isn’t ideal. Good luck!

[Wish You Were Here]

Thanks Hatchetjoe! I read the other threads and maybe I should provide some more info. Besides the Volvo 310 engine, my prop is 19 x 22. Way different than what I am reading on these threads...maybe its the different with the volvo? I have sent the question to my Volvo tech and I'll respond here about what he has to say.

[Tree]

19 x 22 sounds way off on the pitch by a good three inches. What transmission ration are you running. Ideally with the D6 Volvo I’m guessing you’re running around 2500-2600 rpm?

[Tree]

Hatchetjoe - what cupping do you have on that 19x17? I’d say you are under propped by at least an inch. Cupping of the propellor is very important and makes a world of difference.

[Wish You Were Here]

Thanks for response Tree. My Volvo D6 is running at 3000 rpm cruise at 11-12 knots. WOT is 3500 and I get to about 16 knots. I’m not sure what transmission ration is. Can you explain? I’m ready to purchase a new propeller if there any suggestions?

[Tree]

check the top of your gearbox - i suspect its a Hurth 63A transmission probably 2.05:1

[hatchetjoe]

Hi Tree,

The 19x17 I now have has a 5 cup. This is after trying the original 19x19 prop which only gave me 3500-3600 rpm at WOT.

What I was told was that the Yanmar WOT should be at least 3800 to 4000 rpm. I was advised that I would gain 150-200 rpm for each inch decrease in prop pitch so we discussed 17, 17.5 and 18 inch pitch but finally decided on 17. My first run gave me 3800 rpm at WOT. I'm hoping with new bottom paint I may be up to 3900 but I doubt that I will be over 4000.

Thanks!