2950 rpm, 14-15 kts, 10-11 gal per hour, light chop

[tomcat rio]

does that sound about right to you folks with peninsular 300/310 engines in an ablin 28 TE?
it has an zf63iv with a 2.00:1 ration and a 4 blade 18x26 nibral prop.
...
as far as i'm concerned, a flowscan is a must.
thanks

[chiefrcd]

Can't comment on the peninsular diesel but I can vouch for the flow scan. I can't imagine not having it. There are several other brands out there, but regardless...its sure nice to glance down and see exactly what you are burning or to fill up and keep records to the gallon.

[jcollins]

does that sound about right to you folks with peninsular 300/310 engines in an ablin 28 TE?
it has an zf63iv with a 2.00:1 ration and a 4 blade 18x26 nibral prop.
...
as far as i'm concerned, a flowscan is a must.
thanks

Tomcat,
I have the Peninsular. At 2950 I'm 19-20. Fuel flow? I don't know. I don't have a flowscan. My average is 4-5 but I cruise alot around 2500-2700 RPM. For the prop I have a 3 blade 18x18 Nibral.

[tomcat rio]

...what is the transmission type and gear ratio?
i don't think i have the proper prop.
the previous prop was a 3 bladed 18x19..it was faster for a given rpm, but fuel flow was way higher.

[Elizabeth Ann]

Something else to consider. Afterglow does not have a pilot house. Less weight, less wind resistance. This may have some minimal affect.

[tomcat rio]

but i'm not sure that would account for a 4 kt speed advantage.... i think most boats wind up with a less than optimum prop/transmission ratio combination. the only way to get the best combo is to swap hardware around which at least in the case of transmission ratios, isn't practical. even a prop change, if it works will rarely save the enough fuel to pay for itself.
there is a calculator over at boatdiesel.com..its a start, but not perfect by a long stretch.
..
i think basically, an increase in pitch is the same as a reduction in ratio fro the transmission.
in any case, its a black art.

[Elizabeth Ann]

Yeah, I doubt it would account for a 4-5 knt difference either. Anyway, I think I have a recent issue of Motorboating home where they examined the difference btw. 4- and 3-bladed props. I think the 3 bladed prop was faster. I'll look for it later today.

[Elizabeth Ann]

Tomcat,

I found the article. It's in this months Motorboating, August 2006, pg 78. You may still be able to find it on the news stand. I went to thier website, and although searching under props gave a bunch of reading material, this article wasn't found.

The article refers the readers to Michigan Wheel (www.miwheel.com) for a 'prop-it-right' analysis. To sum up the conclusions on a 28' Bertram with newly installed twin Yanmar 260hp. A four blade prop delivers more power and smoothenss. At 3900 rpm The 3 blade cruised at 35mph and the 4 blade at 33mph. Overall 4 blades did not improve low end speed and were slower at WOT.

They tested a 3-blade (19x21) and (2) 4-blade (19x20 and 20x19). Both 4-blades delivered similar results except the 19x20 saw a minimal loss in engine RPM.

-EA

[tomcat rio]

....i might just get a spare 18x18 three blade and stick it on next year. there should be a noticeable difference one way or the other.
thanks
ed

[Tuxedo]

Prop sizing is really not rocket science. You want a prop that allows your engine to turn at least 50 rpm over it's rated rpm in the worse conditions (hot, humid, loaded boat, dirty bottom). Anything less will severely reduce the life of the engine. The Cummins expert over at boatdiesel preaches and preaches and preaches this.

Use a photo tach when testing, tachs are notoriously wrong.

That said, your speed and fuel usage sounds way off. I confessed on this board earlier that I was an Albin dealer in the mid-90s. Seems the Peninsular engines came with a 1.75:1 reduction and 18x17 props, but that was many dead brain cells ago.

[tomcat rio]

prop changes till you get the right numbers. in new york the marinas get a little over $100.00 hour..
..
in the long run, it might make more sense to just do one change during the winter haulout and collect a lot of data for comparison.

[Tuxedo]

prop changes till you get the right numbers. in new york the marinas get a little over $100.00 hour..
..
in the long run, it might make more sense to just do one change during the winter haulout and collect a lot of data for comparison.

Cheaper than an engine.

Seriously, what at you turning at WOT? For every 100 rpm low, take an inch off the pitch. Down here, divers will change the prop for less than the cost of a short haul.

Albin uses, or used to, H&H propeller, and back in the day, they would always work with me on prop sizing. Also, Michigan Wheel has a good prop sizing tool on their web site.

First thing I'd do is find what you're turning at WOT with a photo tach, then call H&H, ask for the Albin rep and ask him for advice.

[jcollins]

Good Morning Guys,
I was trying to keep track of RPM/speed this weekend. I should have written in down. I will make a point to do so next weekend. I did fill up Friday and GPH is around 4. Leaving the marina I opened up to 3400 and was running just below 25. 2700 RPM was 19. I think 2200 was 14-15. I will have Sharon help me with a little chart next week. Over 3000 I am running hot. Just below 200. Finally took care of the slow fuel fill problem. I'll post on the other thread.
I didn't think about the convertible vs. pilot house. Your right.

[tomcat rio]

...transmission ratio?
at wot, i can approach 4000 rpm ( 400 above red line).
i don't stay there long enough to let the speed stabalize.