I recently purchased my Scarab 26 (502 Merc, Bravo 1, 1.5 gear, 25 pitch prop, clean bottom, no paint) and had it surveyed. Surveyor did a compression check and sea trial w/out me present. Both were strong.
He was able to get boat to 63-65 MPH and run the engine up to 4800 RPM. He recommended a more modern prop (vs the old Mirage) and a upgraded exhaust with no water entering the exhaust until the transom to avoid reversion. Good suggestions.
I took the boat for a run with everything fresh from the surveyor and good/new oil levels all around on a 67 degree fall day with water temps at 65.
I topped out at 50 mph and 4100-4200 RPMs with 65 gallons of fuel, plus me and two other adults w/ light gear.
This is my first stern drive. I never adjusted the drive trim (was full down the whole time) and left the trim tabs up and out of the way. Light puttering around saw cooling temps at 115-120 and running at 4000 rpm for a while showed 175 deg F and no more.
Accel was snap on and engine pulled hard and sounded mean and healthy right til 4200 RPM. I was getting just about 50 out of her at this point.
Any opinions? Did I lose RPM because of the drive being down? Am I overpropped at 25 pitch?
I will call the surveyor, but I know you guys know your stuff around here, so I like to have as many opinions as possible.
You need to get the bow up. trim it about half on your gauge, and 25 3 blade is a good prop for your boat, the blade has to be a round ear witch means it is bow lifter not a stern lifter, when you see the tach going up and no more speed trim it done a touch. the ride off a 24 baravo 1 four blade might be be nicer , but you would loose top end have fun
Definitely caused by not trimming the drive.
In my 22' Scarab I could barely get to 50 without trimming. Once you start adjusting the trim to bring the bow up...you'll see (and feel) your speedo climb really quickly.
There probably isn't anything wrong with the boat...don't worry.
Thanks for the input! (forgot to note: prop is 3-blade, older Mirage original)
My ears and other senses were telling me the engine/drive was doing all the right things, as far as working and being mechanically sound and fit. Every mechanical input was what one would want to hear/feel/sense.
I'm not out to run red-line all the time... but I figure that I need to establish that the 502 can redline so that I know all is set up properly.
I will have a chance to play with the trim later this week and get a feel for it. I can't tell you how many other boaters around me are only partial resources. While some know to trim it out, they don't even bother to ask about other engine characteristics or even the prop.
I like the boards here, because if I give all the background info, you guys know I've eliminated other variables. It's nice to know the prop is of proper pitch and that only the lack of me trimming it out seems to be an issue.
I will report back!
Last edited by Philster : 10-12-2009 at 10:58 AM.
Reason: more info
I have a 1997 Scarab 26 with the same 502 MPI and I am spinning a 23 pitch Mirage Plus and just ran it last weekend with two people in the boat and a half a tank of fuel the boat ran 68-69 on the factory speedo. Mine runs about 4900 RPM at wide open throttle trimmed out. If the engine is stock and with WhisperFlow exhaust I think the 25 pitch might be a bit to much. I tried a 4 blade Bravo 1 and in my opinion didn't do much. It had better mid range punch but the boat seems to need more bow lift and the 3 blade seems to do that better. Congratulations looks like a real clean boat. I have owned mine for 8 years and it has been a great boat!
This is all great info. Hey, while we are at it, my tach is slipping/detaching. Is my only option to go thru the panel below the steering wheel? If so, how is it supposed to be re-attached?
I have the same boat and usually when I am running I keep the trim at about 3.5 on the gauge above your throttle and shifter, my speedo and temp gauges also started seperating, the only suggestion that I have is to replace them, the part that is seperating is actually the gasket dryrotting and once the seal is broken you will start getting condensation and the gauge will not work correctly.
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