A B28 Moppie Question

[SoBoSlow]

New to the board but, I have poked around B31 a number of times in the past and love the boats...Thank you Patrick for helping me join.

The reason I needed to join now is, I think I have found the perfect boat for all my needs (right now...since I am not yet ready for a full on B31). Before I pull the trigger I need to finish up a little bit of fact gathering. There is one piece of information I cannot find that I hope the collective experience of B31 can provide some wisdom on.

Does anyone have the stats on a Bertram 28 MOPPIE: Cruise and MPG?

Only data point I can find is one for sale on THT from 2008. Owner reported 200 diesels doing 90 miles round trip and 8 hours of trolling burning 80 gallons. This seems to be roughly in line with similar twin diesel small express boats: Carolina Classic, Henriques and Albemarle. All of which similarly powered would come in at 22-25 kts and 1-1.5 mpg/nmpg.

However, the difference between MPG and NMPG and 1 and 1.5 per makes a big difference on a 240 gallon tank with @ 90-110 miles to some of the far off spots I would like to be able to hit. So, I'd love to dial the data in a little more.

The boat that got me thinking this way is a 1992 with a small tower and twin 230 Volvos with 1050 hours (if you wanted to share thoughts there as well). Don't know if this one proves out to be "the" boat but, it should be pretty close.

Thanks for any help.

[Kevin]

Welcome to the site.
I think your numbers are pretty close for estimation purposes. Rub rail down the hulls should be the same. It all comes down to total weight and how it is distributed along with wind drag(tower) and bottom condition. Two identically powered B28s could have very different cruise speeds. I am on the lower end of the diesel horse power spectrum but I believe cruise a bit faster than average.
Good luck with the hunt.

[Yannis]

I also have B28 FB, yet I shouldn't think the numbers would be so different for a moppie.
I burn 2.6 liters per nm at 2700 rpm on 2X240 Yanmars with 300 hours, doing around 22 knots.
Good luck.

[Hyena Love]

B28 FBC, Yanmar 230/240's. Half tower, no curtains, but loaded relatively heavy.

Conservative estimate of around 1.5 nmpg at cruise. Cruise is 21-23 depending sea conditions and weight.

My typical 14 hour day, engines running all the time, sloppy 2 to 3's, with a run of 60 nm out, mixed bottom fishing and trolling, and then run home burns b/w 85 and 100 gallons.

[Bill Fuller]

I would think the Volvos would do you very nicely in the B28 Moppie. I have the same setup as Yannis and Hyena Love but a few more hours. Half tower with eissinglas all around, 100 gallon live well and the 162 gallon fuel tank (which means about 150 gallons of fuel). And loaded very heavy. Just last year I removed my auxiliary tanks because I never needed them. I now have 4,061 hours on the Yanmars, so I have a pretty good idea what the boat does. I run a bit slower than Hyena Love, typically 17-20 knots, which I think give a little better economy. But I always have the ability to kick it up to 23 (about 2900 RPM) knots if needed. I normally average 1.7-2.2 nmpg depending on the distance, sea conditions, and amount of trolling vs. running. The nice thing about the diesels is you can run at hull speed or trolling speed and get something close to 4 nmpg. Since I retired a couple of years ago the boat is seeing more hours. Also the fishing is in a cycle where I haven't needed to make any 100 mile runs. Over the last 25 years my average distance has probably been 60-80 miles but last year more fishing closer with more time trolling. So last year from May 2014 to May 2015 my boat traveled 4,560 nautical miles with an overall average fuel burn of just about 2 nmpg. As another example, all local fishing within 25 miles of home, I fueled on Tuesday, the GPS said I had traveled 174 nautical miles and I burned 78.9 gallons of diesel. or about 2.2 nmpg.

I think all of us with 28 FBCs agree that you would likely do a bit better than we do with the Moppie. It should be a real nice boat.

Good luck if you decide to go that route.

Bill

[Yannis]

I now have 4,061 hours on the Yanmars, so I have a pretty good idea what the boat does. I run a bit slower than Hyena Love, typically 17-20 knots, which I think give a little better economy

Quite remarkable Bill. I also agree that a few hundred rpm's less, offer substantial fuel economy. I have been advised by Yanmar mechanics though, that these motors like to be pushed to around 3000 rpm's. And that if you run them slow, you should at least push them to 3000 during the last 10-15 minutes so that they get rid of buildups. Right or wrong, I don't have the technical skills to confirm this theory.
You cannot put bigger motors in a 28 without engine room modifications and these 4LHA STP,s take up all height available to the point that the engine cover reinforcements have been shaved off (with cover flexing becoming an issue I will soon have to address). Also, the exhaust tube (all the way from motor to stern) is almost parallel to the sea level so that your turbos are affected by moisture; I added risers for that reason, as well as stainless (not rubber) exhaust terminals that are made at an angle so that they be closed when motors are shut.