33 SF w/ Merc 8.1s performance

jdrc · Post by **jdrc** » Sun Aug 23, 2009 7:17 pm

Does anyone here have a 33 SF with Mercruiser 8.1s (375 hp)? If so can I get some performance #s? Thanks

Rick · Post by **Rick** » Mon Aug 24, 2009 3:01 am

Welcome aboard ! Bob Stansell repowered his but I haven't seen a post from him in a while. You might want to search through a few pages here. I looked at the first 6 and didn't see anything. Capt'n Gene has 8.1's too but he owns one of the newer FBC's. Rick Ticket 85 SF Merc 454 MPI's Falmouth, MA

Post by **dougl33** » Mon Aug 24, 2009 5:44 am

Depending on the how the boat is loaded, I would expect a cruise of 22-23 knots at 3500-3600rpms burning 30-32gph. Top end should be 29-30 knots at 4600+rpms.

Rick · Post by **Rick** » Mon Aug 24, 2009 6:30 am

BTW, if going with the 8.1's....I'd seriously look at the Crusaders instead of the Merc's. Better engine period. But I don't know what the price difference is. Rick Ticket 85 SF Merc 454 MPI's Falmouth, MA

Post by **dougl33** » Mon Aug 24, 2009 8:22 am

I agree.

captgene · Post by **captgene** » Mon Aug 24, 2009 10:14 am

And I really agree. So will Tim Stamm. I did extensive research Merc vs. Crusader. Crusader is hands down a better conversion. I know some 8.1 Merc owners with 200 hrs replaced risers, manifolds and other $$$$ parts. I'll easily have 400 hrs at the end of the summer. Other than oil & filter maint. I've spent $0. (Hope that doesn't jinks me) Gene Dugan Boca Raton, Fl. "Nauti Marie" 1989 33 FBC 2007 8.1 Crusaders

otf · Post by **otf** » Mon Aug 24, 2009 3:56 pm

Capt Gene, any regrets on the gas upgrades? Maybe I am just too cheap, but I really have a hard time with the idea of the diesel money. Hopefully not a concern for another year, maybe more as the original Crusaders are running strong still.

Rick · Post by **Rick** » Tue Aug 25, 2009 4:39 am

Does anyone know how they're getting for 8.1's these days ? Last I heard, they were upwards of $20K.....which is flirting with diesel costs. The power and no smoke of the 8.1's makes them suitable for a lot of guys but it seems the cost benefit is slowly going away. Isn't it ironic that Rudolf Diesel threw himself overboard on a cruise ship because he was sick of all the paperwork ? Rick Ticket 85 SF Merc 454 MPI's Falmouth, MA

IRGuy · Post by **IRGuy** » Tue Aug 25, 2009 6:29 am

Rick.... You are correct about diesel pricing. I can get "remanufactured" 330 HP Cummins 6Bs for just about $20,000, with harnesses, gauges, etc, and with standard new engine warrantees.

otf · Post by **otf** » Tue Aug 25, 2009 8:21 am

interesting

amarok · Post by **amarok** » Wed Aug 26, 2009 4:56 am

Here is Bob Stansil's post! Posted - 08/07/2007 : 4:36:25 PM ________________________________________ I have a 86 33sf that I repowered with Merc 8.1's two seasons ago. The engines are Smartcraft which allows you to get very accurate readings on lots of things including fuel burn. Depending on sea conditions these are average numbers. 3000 rpm-19knts-26gph, 3200rpm-21knts-30gph, 3400rpm-22knts-34gph, 3600rpm-23knts-36gph. In muy opinion the boat does not like 19 - 20 knots and you use the trim tabs extensively. At 22knts the tab use is reduced and at 23 knots ionly use the tabs to correct side to side balance. The boat really likes 23 and above as it is completely up on the strakes and the bow comes down. As I said it is effected by load and sea state. Bob Stansell 86 SF "Apres Ski" Cohasset, MA

captgene · Post by **captgene** » Wed Aug 26, 2009 5:30 am

Scott, No regrets on the 8.1 Crusaders. When I bought this boat, I figured in 2 yrs. the old Merc 454s would be done, but they ran 7 yrs. The reliability was almost zero, but still running. Of coarse I always wanted to go to diesel, but when I did the math, the 8.1s were the most affordable. In South Fl. we still have non E-10 available. The numbers Doug posted are about right on. I can cruise at 21-22 kts and burn 30 gal/hr. I think I paid $13K ea. for the engines and the Hurth gears. Crusader thru in the Cruise control and Murphy computers for cost. They wanted somebody to have them to show. I wouldn't have been able to afford them otherwise. Being friends with the Crusader dealer and doing most of the work myself helped a lot too. Gene Dugan Boca Raton, Fl. "Nauti Marie" 1989 33 FBC 2007 8.1 Crusaders

Bob S · Post by **Bob S** » Wed Aug 26, 2009 8:17 am

JDRC I noticed that some reposted my performance figures. Thanks as I have been away. As far as the Merc 8.1's are concerned they have been great. I mentioned on the site last year I had one problem that Merc stepedp up and took care of even though they were out of warranty. It was a faulty fuel cooler and they sent a new one no charge. The performance # really haven't changed and if I were to do it again I wouldn't hesitate to go gas. I think the 33 is right at the threshold where it can use gas or diesel. For me the gas install was far more economical and the boat runs fantastic. I would be happy to show you the install if your are local in the Boston South Shore area. Boat is for sale by the way so if you are looking for for a very clean and completely redone 33 SF let me know.

jdrc · Post by **jdrc** » Wed Aug 26, 2009 7:26 pm

Thanks for the feedback! Your fuel burn was about what I expected, but the performance is a little better than I expected. A few months ago I purchased a 1981 33 SF that was badly neglected, but the price was right. The 454 Crusaders that were in it are shot. I picked up a pair of Merc 8.1s with 220 hrs for $8,000/pair. Looks like my B 28 may be sold so the 33 project is about to go into high gear! Hopefully in time for the next Rendezvous. Bob, mind if I ask what tranny, ratio, dia./pitch ? I was planning on using ZF 63A 2:1 w/20x20 wheels. Thanks, Jeff

Post by **dougl33** » Thu Aug 27, 2009 4:38 am

Jeff, Where are you located?