Mercruiser 357 question

[Tominator88]

Hello I bought a boat with a 357 merc part number 865108r88 it is connected to an alpha but has its own raw water pump when I look up the part number it shows an engine without the raw water pump but mine clearly has one and I believe it’s factory I’m about to get this rebuilt is it possible I have the bravo version 325 hp the part number says otherwise the alpha version has 275 hp does anybody have experience with these I’d really like to meet in the middle with 300hp I’ve read it’s mostly the cam and jetting is that true should I be looking at the bigger cam as part of my rebuild thanks in advance I currently have a non vortec freshly rebuilt 5.7 in my 24’ Grady white offshore and I’m unhappy with the speed I’m assuming my existing 5.7 is 260 hp I would like to gain more that 15 hp with this upgrade

 

[dubs283]

If the engine/alpha package is closed cooled oem then there are two raw water pumps. One mounted on the engine (inboard/bravo style) and one in the drive (alpha style)

 

[Tominator88]

Thanks it is not a closed cooling system

 

[kenny nunez]

Is there a “Y” pipe connecting the drive pump water to the incoming through hull fitting?

 

[Fun Times]

Try having a look at the ignition control module sticker as sometimes there will be information on it that says if the engine is a bravo, or alpha model.

What year is the boat and is the stern drive an alpha Gen 1 or 2?…
NOTE: If used with an Alpha One (GEN I) drive, this engine requires a Seawater pump kit 46‑807151A5 & Serpentine belt kit 807901A5 (sold separately) for proper cooling.

357 merc part number 865108r88 = https://www.mercruiserparts.com/865108r88-357-alpha-4v-rm

 

[Tominator88]

Their is a through hull for the water and yes it’s I could be an alpha one so I must have that included kit thanks now does anybody know where I could find parts breakdown on these motors I want to get a look at what cams they both have

 

[Fun Times]

Here will be your engine parts catalog for this alpha engine model,

357 Alpha 4V - 1G400000 & Up

357 Alpha 4V - 1G400000 & Up

www.mercruiserparts.com

 

[Scott Danforth]

the 357 is a merc reman vortec headed roller motor with flames on the beauty cover

a simple cam change will get you to over 300hp. however the published limit of the alpha drive is 300hp.

being a roller motor, you should only need the cam and a carb spacer to add plenum volume to be about 325hp at the crank, 300 at the prop I would look at the XM264HR cam. remember, do not go over 270 degrees duration with a wet exhaust.

a bravo will have a crank driven raw water pump

an alpha with a heat exchanger will have a crank driven water pump AND the water pump in the drive.

certain alpha gen 1 require the kit indicated above.

 

[Scott06]

Hello I bought a boat with a 357 merc part number 865108r88 it is connected to an alpha but has its own raw water pump when I look up the part number it shows an engine without the raw water pump but mine clearly has one and I believe it’s factory I’m about to get this rebuilt is it possible I have the bravo version 325 hp the part number says otherwise the alpha version has 275 hp does anybody have experience with these I’d really like to meet in the middle with 300hp I’ve read it’s mostly the cam and jetting is that true should I be looking at the bigger cam as part of my rebuild thanks in advance I currently have a non vortec freshly rebuilt 5.7 in my 24’ Grady white offshore and I’m unhappy with the speed I’m assuming my existing 5.7 is 260 hp I would like to gain more that 15 hp with this upgrade

Your art number does translate to the alpha / 275hp version

I looked at these engines when I repowered I think the difference is in the cam - https://www.marineengine.com/parts/...000-up/cylinder-block-camshaft-and-crankshaft

part #11 has different cam part numbers for alpha and bravo.

Also different are the ignition modules and carbs - not sure if timing is different in ignition module, look like they use same primary metering jet, different secondary jets (.092 vs .098) and different metering rods.

Yes a non vortec is 260 hp, vortec you see different rating thrown around 295-325 hp. So doing the cam swap Scott recommends or using the merc cam should get you over 300 for sure.

Do you have a gen 1 or gen 2 drive. If you have a heavier boat plus more power may be an issue but you can cross that bridge when you come to it.

 

[Scott Danforth]

Merc used to use crane cams. Difference in ignition modules is one has shift interrupt, one does not. A bravo requires no shift interrupt whereas the alpha does require a shift interrupt

 

[Scott06]

Merc used to use crane cams. Difference in ignition modules is one has shift interrupt, one does not. A bravo requires no shift interrupt whereas the alpha does require a shift interrupt

Not sure it is just shift interrupt on the modules. If it were merc could use the same module with a bravo as shift interrupt never gets tripped. of course they do different modules for same hp alpha and bravo modules so who knows….

 

[Scott Danforth]

I agree, they could. But for some dumb reason they don't. Then again, they have 5 part numbers for the same oildyne hydraulic pump

 

[Tominator88]

Thanks so much I’m going to be ready through those links tonight about the part numbers sombody got rid of the thunderbolt ignition and installed a delco one I think? I needed a shunt to time it and I got a new ignition modual from my merc dealer (bills outboard in hingham Ma) love that place parts guy Paul is so good I never imagined the ignition having much of an effect on power mine does have the shift interrupter I am gentle on the throttle but my with my existing engine in cruising around 20-22 mph I just need a little more or I’m going to be raving this thing to high thanks for all the reply I’ll ask my engine guy about that cam

 

[Tominator88]

And yes it is a marine distributor I said delco but it’s like the delco but it’s a sierra

 

[Scott Danforth]

the thunderbolt ignition is 10x better than the delco. Not sure what brand Sierra is private labeling. I know that the recent line of Sierra distributors are the old Mallory YL units (sold at twice the price)

 

[Scott06]

If the delco works leave it. The problem with the Thunderbolt is if you need an ignition module , the delco system is cheaper than a module. Additionally now a lot of modules are NLA.

if you really want more power and maybe it’s in a larger boat, put a stroker crank in it when you rebuild it.

 

[Scott Danforth]

if you really want more power and maybe it’s in a larger boat, put a stroker crank in it when you rebuild it.

^^^^^^ This