350 MAG Bravo 1 Performance Issue?

Joesolta

Cadet
Joined
Jan 19, 2019
Messages
25
Scott, Chris. It's a Bayliner and their designs are not exactly "optimal". Performance and efficiency seem to be afterthoughts relative to low price and superficial and cheap features. The 2252 Ciera was a cruiser that was built on the lower hull of a bowrider that probably weighed 1500 lbs less. Anyway, it does the job for what I need, mostly inshore fishing in the PNW and commuting to the cottage. I'm too cheap at this stage of life get something better so it will have to do.
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
Joined
Jul 23, 2011
Messages
47,304
Bayliner boats were intended to be entry level boats. Bayliner took "liberties" to get shorter cuddies and other product offerings in that entry level price point.

use the heck out of the boat, then when you want bigger, faster, different....sell and get the next boat you want.
 

QBhoy

Fleet Admiral
Joined
Mar 10, 2016
Messages
8,286
I’d say that great going for that boat. They aren’t quick hulls and have the aerodynamics of a brick.
Youre a little off with your stated target rpms though. The rev range is 4600-5000 rpm for that engine.
At 5100rpm you are just about at the limiter. Dare I say it....you could perhaps go an inch up in pitch and see a little gain in speed, whilst coming back into the recommended rpm range...All the best.
 

QBhoy

Fleet Admiral
Joined
Mar 10, 2016
Messages
8,286
I tried a 19" Prop some time ago but found the top rpm would not quite make it not the target range with a heavy load. I don't want to stress the engine too much.
What kind of prop slip #s do you guys get?

Your target range is not what you think it is. It’s 4600-5000. Better towards the top of that range but not over. You currently are, or your rpm tacho is wrong or on a V6 setting. Is this a re engined boat ?
 

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Your target range is not what you think it is. It’s 4600-5000. Better towards the top of that range but not over. You currently are, or your rpm tacho is wrong or on a V6 setting. Is this a re engined boat ?

Nothing wrong with a hundred revs over... That's how I have mine set up and for the conditions I operate in it's fine. In fact, is better than the 'right' prop...

If the tacho was on the V6 setting, then it would be indicating 6000 at 4500 engine revs. I doubt that's the case.

Chris
 

Joesolta

Cadet
Joined
Jan 19, 2019
Messages
25
QBhoy my Mercruiser manual says 4800-5200 for this engine. I haven't looked (yet), but it's probably roller lifters so they give it an extra few rpm. Although I get 5100 with a light-ish load, it's probably closer to 4900-5000 heavy, so that should be good.

Achris, I have both an analog tach (set for 8 cyl) and the Mercruiser digital display fed from the ECM so the rpm is accurate.

Thanks guys, I think that the average of the various opinions is that the numbers I have are not unexpected for this type of boat. Although, it's only 22.5 ft, the weight and high windage for it's size are limiting factors. I will try a slightly larger diameter prop to try to get the slip down. A lower angle of attack should improve efficiency a bit.
 

bman440440

Petty Officer 1st Class
Joined
Apr 4, 2011
Messages
266
this is just my opinion but I would prop the boat for your normal load... I.E. full 5200 RPM's with a heavy load... and just be mindful when you are lite...thats how I have done mine and all my buddys boats and performance is great as well as fuel burn (across all the boats)... and being that your prop slip is so high I would go to a 4 blade 17x14.5... yes you are losing diameter but you are getting an extra blade... your current prop is 3x17x15.5 correct? is it stainless?
 

Joesolta

Cadet
Joined
Jan 19, 2019
Messages
25
bman, i would agree that it's better to keep the rpm in the high range. I'm going to try a 4 blade also but I don't expect any large improvements. The current prop is alum. but I had a stainless in the past. it dropped the rpm (with same pitch) a bit but no noticeable change in mpg on the computer.
 

bman440440

Petty Officer 1st Class
Joined
Apr 4, 2011
Messages
266
being that its aluminum I would go with the turning point 21501740... And I think you would be really close to your target RPM of 5200 when loaded... If you you get it at west marine you can swap out the prop for free if it is not the correct pitch(as long as its not damaged)... I have that prop on my 20' maxum with a v6 swinging the 21" version and I love it!! it has dual blade profiles so it has great hole shot and top end too... I have 2 props and was going to run the other (standard alum 4 blade 19") I have for fishing and the 21 for tubing/skiing and found that I never needed to change it out... it works great loaded with 3 250+ pound guy's, 32 gal bait tank, 47 gal of fuel, 100 lbs of ice in a kill bag and all out other fishing gear (9 rod/reel combos, ice chest full of food/beer) as well as when we are loaded with 7-8 people on the boat doing water sports... loaded for fishing about 500-600 lbs more than water sports I can get about 47-48 MPH (@4850-4900 rpm) and water sports load about 55 mph with pulling back a little on the gas to keep it at the same RPM's... when I'm light its a true rocket ship and I need a light hand on the throttle because I will be at redline in less than 8 seconds and thats how I found out that I have a RPM limiter that kicks in at 5200 RPMs
 

QBhoy

Fleet Admiral
Joined
Mar 10, 2016
Messages
8,286
QBhoy my Mercruiser manual says 4800-5200 for this engine. I haven't looked (yet), but it's probably roller lifters so they give it an extra few rpm. Although I get 5100 with a light-ish load, it's probably closer to 4900-5000 heavy, so that should be good.

Achris, I have both an analog tach (set for 8 cyl) and the Mercruiser digital display fed from the ECM so the rpm is accurate.

Thanks guys, I think that the average of the various opinions is that the numbers I have are not unexpected for this type of boat. Although, it's only 22.5 ft, the weight and high windage for it's size are limiting factors. I will try a slightly larger diameter prop to try to get the slip down. A lower angle of attack should improve efficiency a bit.

Hi joesolta

im 99% sure your engine is 4600-5000 rated. It says so in the manual I have and everywhere else I’ve looked. Are you defo looking at the specs for the right engine ?
 

thumpar

Admiral
Joined
Jun 21, 2007
Messages
6,138
I have the Turning Point 4 blade stainless and have really been impressed with it. I had a stainless 3 blade before.
 

scoflaw

Ensign
Joined
Jun 2, 2010
Messages
962
As mentioned, 200 extra rpm,s is no big deal. That ECM has a rev limiter also, so maybe his tack is off a bit.
 

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Specs for SBC 2001- up. 350 Mag MPI 4600-5000rpm. (See below) I'd be happy with it at 5100. Prop it down a little and the bottom end will suffer. Hole-shot will suffer, driveability will suffer. Unless you are flat-out racing on dead smooth water, I always prop high. 100 over is my target. When you're up and down swells, or the breeze is in and you've got a sloppy trip home, you'll be more than glad of the lighter prop. Makes the boat significantly easier to drive.

350mpimagspec.PNG
 

Joesolta

Cadet
Joined
Jan 19, 2019
Messages
25
Mercruiser manuals seems to be all over the map. This is an owners manual dated oct 2007. My engine is 2009.
 

Attachments

  • photo307388.jpg
    photo307388.jpg
    217.5 KB · Views: 0

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Mercruiser manuals seems to be all over the map. This is an owners manual dated oct 2007. My engine is 2009.

I would go by your owner's manual... Also, it should also be on the engine cover. You'll have serial number, a bunch of other specs (Spark plugs and gap, etc) and the WOT recommended.... If that also says 4800-5200, then ignore us, go by that....

Chris....
 

QBhoy

Fleet Admiral
Joined
Mar 10, 2016
Messages
8,286
That’s not your engine. Yours is a 350 mag mpi surely. Although to be fair. It’s usually only the mpi that is 300hp on the 5.7
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
Joined
Jul 23, 2011
Messages
47,304
No problem spinning the motor to 5100 or 5200.

The rotating assembly has no idea what induction system is on the motor
 

QBhoy

Fleet Admiral
Joined
Mar 10, 2016
Messages
8,286
Ok. So it seems the seacore model 350 mag mpi is for some reason rated at up to 5200 rpm. Weird. Only difference is it’s fresh water cooled and closed system.
If yours is closed cooling with internal cooling, i apologise. If it isn’t, it’s 4600-5000.
Mine is the latter and I can tell you that it hits the limiter below 5200 rpm for sure.
 

Joesolta

Cadet
Joined
Jan 19, 2019
Messages
25
Yes it's a Seacore which includes closed cooling, anodized castings and additional stainless hardware.....except it appears, for the steering swivel shaft (!) which is now slowly leaking!! I see this topic is thoroughly cover in the forum.
 
Top