3000 W/Alpha Outdrives

[GC Capitol]

Good Morning, I am a newbie to the site but the information from what I have seen is very good! I have a 98, 3000 SCR that I am in love with and have owned since 2002, although I have never been real happy with the pick-up and top end of this boat, If I have over four people on board it is very sluggish coming up on plane, I have never had the engines go over 4200 RPM's at full throttle and usually cruse is about 27-28 kt's with top end of 32-34. Does anyone else have 5.7's with Alpha outdrives that we can compare? TIA

GC

[ss3964spd]

Which 5.7's are installed GC?

If they are only getting to 4200 at WOT it would seem the boat is over propped. Do you know which props are installed?

Dan

[GC Capitol]

They are the 5.7 EFI, and no I do not know which prop's are installed, I am getting boat hauled and checked for prop's and am beginning to think SS, but also wondering about pitch.

[ss3964spd]

The EFI 5.7's should be in the neighborhood of 300 HP. I'd expect that size boat with twin 300 HP 5.7's to probably top out around 45-ish - with the right props of course, even if they are aluminum props, which they probably are.

I think there is a prop size calculator on the Mercruiser web site - might want to check that out. http://www.mercurymarine.com/propellers/prop-selector/

Dan

[GC Capitol]

Thanks Dan,

The HP is 260 so I would think that you are correct with that amount of HP we should be fine. When all the conditions are right and I have clean bottom, no weight on board we do pretty good but any thing out of ordinary and all goes to.... well you know.... LOl Thanks, Kevin

[ss3964spd]

Hmmm, thought the EFI 5.7's were more than 260. With twin 260's I'd guess WOT should get you to somewhere in the area of 40 MPH, but I'd guess twin 260's are probably about the minimum for that size boat - which is probably why it all goes to hell when loaded. Different props may help with getting it on plane faster but at the expense of top speed. Stainless props may also help as they don't flex as much as aluminum. Unfortunately, until you know what props are on it there's not much you can do.

Dan

[destination unknown]

Ok here we go.

I have a 1997 3000SCR with twin 5.7 EFI with Alpha Gen II and SS props. I also have a Flo Scan on board so my numbers are good. Ever since day one the following info applies:

HP is 220 hp per engine for the 1997 5.7 EFI, they are actually TBI engines. The 1998 version is 260 per engine if it is a true EFI, you need to take your engine serial number and look it up on Mercruiser's web site. From what I am told from a handfull of mechanics and from Mercruiser themselves all they did was calculate HP diff before and after 1998.

As per my Flo Scan at 3700 RPM, I get between .95 and 1.2 MPG between both engines at a best cruise of 27 mph to 33 mph. Variation is based on wind, tide and weight on board.
WOT I run up to 4700 to 4900 rpm and top off at 37mph, thats on a smooth flat bay.
Below 3400rpm she comes of plane. 3700rpm is really the sweet spot.

To get on plane I push throttles to 90% and when I get to 4400 rpms I back off to 3700. about 20 to 30 seconds to plane. If a lot of weight on board I put tabs full down and she jumps right out of the water.
I never use engine trim runs best with outdrives tucked in and just a little of port tab to level the boat out.

Props are Michigan Wheel SS Raptures 14.25 x 21

Hope this helps any other questions just ask, I have the boat since 2000.

[seapuppy]

good info....but I thought the 5.7ci EFI engines topped out at 5200rpm.....but still ...please rely on your manual to tell you what the wot is supposed to be for your model and engine/drive combination...

SP

[destination unknown]

WOT Range for 1997 5.7 EFI @ 220 HP 4200 to 4600
WOT Range for 1998 5.7 EFI @ 250 HP 4400 to 4800

[seapuppy]

ok...so...you should be hitting somewhere between 4200-4600rpm at wot....wide open throttle...

SP

[GC Capitol]

Thanks Guy's great information, I had starboard Engine replaced in later part of 2002, still have original booklets on original engines and had long block engine installed, both matching 260HP as per the manuals, and they did say 4400 to 4800 RPM's, which seemed a little high to me especially since I have never seen 4300 RPM's.
Again if I have just cleaned and painted the bottom and conditions are right I can get four people on plane with about 5/8 full fuel tanks and about 20 gallons of water/sewage (I usually try to keep sewage pumped and water to about ten gallons if anchoring out) but if conditions are not right or I have any barnacles, I cant even get up to 4000 RPM's, I looked for #'s this weekend but paint build up would not let me see anything, I am having them pulled and and borrowing a couple of different pitches to see what works, as well as having bottom cleaned again (had bottom cleaned in April) and usually paint bottom in mid June as I am on Potomac River close to Chesapeake bay and have heavy briny water here so it really is a challenge to keep your bottom clean especially when you have an extended warm season as we have had here..

Destination Unknown, I have had good luck getting on plane pushing engines up to 4000 RPM's then backing to just over 3800 RPM.s
seems to be the sweet spot, when conditions are right I can push engines to 4100 rpm's WOT and run about 32 to 33, but never have been able to do better since owning the boat since 2002, I have questioned the props before and been told they were just fine but after having continuous problems with OD's I am seriously thinking I have different issues causing the OD problems

PS Thank You All for your help it is very useful information

[ss3964spd]

GC,

Once you have the boat up on plane do you trim the drives up at all? How about the trim tabs - do you get them out of the water as much as you can? I know on my little boat doing both will easily add 2 or 3 hundred RPM's without touching the throttle.

What problems have you had with the OD's? One thing you might consider is having the ignition timing verified on both engines - just make sure the person doing it knows how as there is a specific procedure. Also verify that the throttles are opening all the way when at WOT.


BTW - we're also on the Potomac but considerably up river from you. The farthest down river we've been is Colonial Beach.
Dan

[GC Capitol]

Hello Dan,
I have found out that the props are 14x20Pxfour blade

[ss3964spd]

GC,

You might consider finding out what the original props were and go back to those to see if they work any better.

Dan