290sundancer
New Member
What size diameter prop should I have on 1990 270DA, I found the pitch on Sea Ray site its 19(should the diameter be 14, 14.5, 15)
Prop size?
- Thread starter 290sundancer
- Start date
CAGE RATTLER
New Member
I havent been on the site very much (to busy fishing) and i see this a lil older thread, but from my findings (thanks to other members here) is the larger diameter on the bravo1 the better.
I put in a new 496 MAG MPI in my 255 amberjack this season and had to dial in my prop for it. I ended up with a 19P Mirage plus stainless steel prop and if you havent tried a SS prop on your boat, demo one and you'll be amazed!! The difference between SS and aluminum was incredible.
Not sure what HP your 7.4 is but i would suggest trying a 17 or 18 pitch mirage plus and then adjust from there after doing a WOT test run.
I put in a new 496 MAG MPI in my 255 amberjack this season and had to dial in my prop for it. I ended up with a 19P Mirage plus stainless steel prop and if you havent tried a SS prop on your boat, demo one and you'll be amazed!! The difference between SS and aluminum was incredible.
Not sure what HP your 7.4 is but i would suggest trying a 17 or 18 pitch mirage plus and then adjust from there after doing a WOT test run.
EricW
Member
- Mar 16, 2008
- 354
- Boat Info
- 1994 290 Sundancer
- Engines
- Twin 2005 220hp 4.3 MPI's FWC w/ Alpha 1 Gen IIs
+1. With a 7.4, Bravo I combo on a 270, you should run an SS prop with at least 15" diameter. Like Rick said, the Merc Mirage Plus 15.25x19 is a great choice. A Merc "Revolution 4" 4 blade might even perform a bit better, but expensive.
If you're on a budget (and who isn't) Mercury's "economy" Thunderbolt SS prop is an excellent choice. Same exact dimensions as the Mirage Plus, but no polished finish. New, the Thunderbolt costs about $150 less than the Mirage Plus.
If you're on a budget (and who isn't) Mercury's "economy" Thunderbolt SS prop is an excellent choice. Same exact dimensions as the Mirage Plus, but no polished finish. New, the Thunderbolt costs about $150 less than the Mirage Plus.
CV-23
Active Member
- Jun 25, 2010
- 1,891
- Boat Info
- 1990 270 Sundancer, 2003 Ford Excursion 4x4 Limited
- Engines
- 454 merCruiser w/Bravo 1
I run a 4 blade stainless thats 14.5" x 18P with my 1990 454....puts me right at 4500-4600 WOT. GPS speed is 38mph. My hull is bottom coated, Mike.
MarkD
Member
Wow, I had a totally different experience (10 years ago) with my 1990 270. Stock prop was 15.25 x 17 Mirage SS. I was interested in cruising at 3200 rpm as well as eliminating the SS which caused galvanic corrosion in fresh water. I usually ran with a full load of water, fuel and gear and never had a prop that had the characteristics I desired. The issue with this boat is:
1) its very long & narrow with a sharp deadrise and is hard to keep on plane at lower rpm
2) single engine/Bravo 1 with lots of torque which causes alot of strain on the prop hub centers.
3) Boat is fairly heavy for a single engine setup.
My issue was that I found the perfect prop, a 16x16 aluminum 3 blade mercury. This had the big ears (looked like mickey mouse ears) and planing characteristics I wanted. It "could" plane my boat at 2900 rpm and would do ~4250 on the top end. Best speed was 3300 rpm and 27 mph. The best part was that my idle speed picked up almost 1mph and was easy to handle around the dock since it had more bite. The worst part was the hub center would blow out (i.e. spin) when it was heavily loaded. The darn thing just wasnt strong enough to handle the weight (I tried using every hub center known to man). I finally ended up with the next best thing which was a 4 blade SS from a company called Prop tech. It was a 15.5 x 17 pitch prop. Similar characteristics although not quite as good low end. Never had hub center issues again... I guess something about SS just gives it more strength....
good luck.
1) its very long & narrow with a sharp deadrise and is hard to keep on plane at lower rpm
2) single engine/Bravo 1 with lots of torque which causes alot of strain on the prop hub centers.
3) Boat is fairly heavy for a single engine setup.
My issue was that I found the perfect prop, a 16x16 aluminum 3 blade mercury. This had the big ears (looked like mickey mouse ears) and planing characteristics I wanted. It "could" plane my boat at 2900 rpm and would do ~4250 on the top end. Best speed was 3300 rpm and 27 mph. The best part was that my idle speed picked up almost 1mph and was easy to handle around the dock since it had more bite. The worst part was the hub center would blow out (i.e. spin) when it was heavily loaded. The darn thing just wasnt strong enough to handle the weight (I tried using every hub center known to man). I finally ended up with the next best thing which was a 4 blade SS from a company called Prop tech. It was a 15.5 x 17 pitch prop. Similar characteristics although not quite as good low end. Never had hub center issues again... I guess something about SS just gives it more strength....
good luck.
MarkD
Member
Quint, That price is a big hit, but i dont think its that much more than most 4 blade SS props in that range (i probably paid near 500 10 years ago). I was willing to pay that for the benefits I received from it. It solved alot of my issues, except for the corrosion one. Stainless is a pain in the butt when in moving water that is fresh. You have to use magnesium anodes and keep your Mercathode system in perfect shape.
This conversation of props made me think of when I blew out my first hub center just before going away for a long weekend with another couple.... I went to a boat supply company called Post Marine in NY. They recommended a SS replacement prop. 14.24 x 17 pitch (stiletto??? maybe). I bought it for $450 and went on my way. It worked like crap! i had to run 3700 rpm just to stay on plane, and i was only doing maybe 24 mph!!!! i returned it.... That was the worst performing setup you could imagine.
This conversation of props made me think of when I blew out my first hub center just before going away for a long weekend with another couple.... I went to a boat supply company called Post Marine in NY. They recommended a SS replacement prop. 14.24 x 17 pitch (stiletto??? maybe). I bought it for $450 and went on my way. It worked like crap! i had to run 3700 rpm just to stay on plane, and i was only doing maybe 24 mph!!!! i returned it.... That was the worst performing setup you could imagine.
CAGE RATTLER
New Member
I wound up getting a mirage plus prop for my boat that worked out perfectly for me.
I was demoing props from a local shop and the 19P im demoed that was perfect was a used prop and got it for $250. A huge savings compared to the $660 new price. It had some light surface rust but cleaned up nicely. Might want to check out some shops in your area for used to save a little.
I was demoing props from a local shop and the 19P im demoed that was perfect was a used prop and got it for $250. A huge savings compared to the $660 new price. It had some light surface rust but cleaned up nicely. Might want to check out some shops in your area for used to save a little.
CAGE RATTLER
New Member
Thats true ............. when i was demoing i wanted to try a 4 bladse and they didnt have any.
Phlorida
New Member
- Sep 15, 2010
- 867
- Boat Info
- 1995 250 Sundancer
- Engines
- 5.7L Mercruiser w/Bravo II
My requirements are identical to yours but my configuration is somewhat different with a 5.7L B2. I've currently got the OEM 17.5 x 23p AL prop that turns 4500 RPM WOT. How do you get from there to a larger diameter, four blade, SS prop? What size are you considering for your boat?
