Upgrading mercruiser 350 v8 260 hp

[fabrimacator21]

Re: Upgrading mercruiser 350 v8 260 hp

Sportsmans II Iron Heads from world products are saying its an improvement of 30-70 HP. I found some on craiglist for $300 for both. 1 Needs a small crack welded though. But prices on Summit raceing is anywhere between $400 and $700. Will this work? Good or bad idea?

http://www.worldcastings.com/products/sportsman-ii-iron-heads.html

http://www.summitracing.com/search/?keyword=SPORTSMAN II Iron Heads&dds=1

The sportsmans are not ideal for your setup... 200cc intake runners aren't great for tq. Geared more toward a street rod looking for more top end then low end. You want 170-180cc heads(good tq).



Vortecs (170cc runners) can be had dirt cheap and will make the same power. If I were you I'd buy a set of vortecs that need a valve job and pay to have them rebuilt.... while he's in there to rebuild em have him do some port work. Vortecs are great torque heads and with some port work can really come alive on the top end.

http://performanceparts.com/part.php?partID=405559

Or you can buy a set of these ^^^^ which is the way to go IMO. 27 more cfm flow at .500 lift then the stock vortecs AND they will accept the older style intake manifold so your not stuck with expensive aftermarket vortec manifolds. They also have larger valves then stock vortecs. Price isn't bad either.

Depending on how much a valve job and port work is gonna cost I'd say your best bet is the RHS heads.

 

[Cptkid570]

Re: Upgrading mercruiser 350 v8 260 hp

Knightowl - what size propellor do you have on there now? You seem to be avoiding this question.

 

[knightowl]

Re: Upgrading mercruiser 350 v8 260 hp

I am avoiding that question because i just got a brand new prop and yes its a few miles slower then my old one but the power seems a lot more consistent then my older one when pulling a tube. Plus it makes a bigger wave!! It?s a 4 blade prop, 992202. That?s all that says on the receipt. I can find out what pitch by calling the local store i got it from. I physically took my boat to a propeller specialist that deals with ONLY marine prop's and big ship props.. These guys been around for awhile now and he recommended me this prop because he said you will get a good bite out of it and it will have a lot of control when using this prop. Also the IDL speed will be slower and better for parking from what i had. He said it would make a better trolling prop too.

From my point of view when i took the boat out, seems to be a small improvement in the docking speeds/turning and reaction. But not worth losing a few miles over. However the waves are amazing and the power seems to be an improvement but lacks in top end speed.

I just might go back and ask for a different prop. I am afraid if I get the top speed one and then try pulling and tube it would bug down the engine and boat too much and wouldn?t pull as good.. What are your opinions? Ive also heard of the spring loaded props. Are those worth it?

(Another note, my trim cylinders are shot and needs replacing. I just bought a new trim cylinder repair kit and will be repairing them today. I will test the boat out this weekend hopefully. When cruising, I can?t raise or lower my trim unless I?m stopped. Also my outdrive drops down in about 10-15 minute of time.)
Also when boat in water I still see there is room in the trim cylinder shaft to go inside like 4? however the trim looks to be dropped down normal 90degrees.. If only those 4? trim cylinder shaft would slide in any more inside it would force my boats front end to drop and I think I could get a few more miles out of it. Instead my front rides high at times.) Is it possible when I go at high speeds my outdrive raises up a little bit due to bad cylinders?

 

[knightowl]

Re: Upgrading mercruiser 350 v8 260 hp

The sportsmans are not ideal for your setup... 200cc intake runners aren't great for tq. Geared more toward a street rod looking for more top end then low end. You want 170-180cc heads(good tq).



Vortecs (170cc runners) can be had dirt cheap and will make the same power. If I were you I'd buy a set of vortecs that need a valve job and pay to have them rebuilt.... while he's in there to rebuild em have him do some port work. Vortecs are great torque heads and with some port work can really come alive on the top end.

http://performanceparts.com/part.php?partID=405559

Or you can buy a set of these ^^^^ which is the way to go IMO. 27 more cfm flow at .500 lift then the stock vortecs AND they will accept the older style intake manifold so your not stuck with expensive aftermarket vortec manifolds. They also have larger valves then stock vortecs. Price isn't bad either.

Depending on how much a valve job and port work is gonna cost I'd say your best bet is the RHS heads.

How my HP and MPH do you think i can gain from those RHS heads?

 

[HT32BSX115]

Re: Upgrading mercruiser 350 v8 260 hp

By the way what prop would you recommend for my boat? Why is my tach gets screwy after 4 rpm? Also, if i had to do it all over again which engine should i have bought for this boat and what type of out drive?

Check out this lucky son of gun!

http://www.youtube.com/watch?v=T79b3hXrHXw

Howdy,


Nice job on the restoration!!

First of all you NEED to fix your tach (and ensure that it's correct) it sounds like a wiring problem or a poor connection.

Second, you need to determine what your WOT RPM REALLY IS.

If it's only 4000, YOU ARE SERIOUSLY OVER-PROPPED. (period) That will kill your top end, and hole-shot and in extreme cases, will prevent you from planing and could "break" your engine.


What is your current prop pitch and drive ratio?

In a boat that big the ratio should be around 2.00:1

A 4 blade prop might be ok if the pitch is right but you won't know until you know your current (GPS) speed, WOT, RPM & drive ratio.


As far as switching to a Bravo....I would put a big-block (454/496) and a 2.00:1 Bravo III in that boat. It would be as involved as R&R'ing the engine, gimbal and drive. (It appears that you have already got that experience)

I watched that twin turbo video.

If that engine goes into a closed engine compartment boat, it will be an accident looking for a place to catch fire (non-jacketed turbos) And it if kills someone the lawyers will have a field day.



Cheers,


Rick

 

[n2ostroker]

Re: Upgrading mercruiser 350 v8 260 hp

Stick with what you have and save your money for later. If you go adding heads you'll need to change exhaust manifolds too to a newer style and better flowing. Then you'll need to adapt that to your existing exaust. Then a carb or at least a jetting change and an intake manifold. The list goes on....... Then you're still stuck with a 350 in a large boat. No matter how you cut it you'll be lacking the torque needed to really get it up and going.

Going with the Vortec stuff would be a huge improvement if you wnated something to last till an upgrade to a bigger motor. It would give a fairly large torque increase and quite a bit of hp and as mentioned be dead reliable.

I would put an Edelbrock Performer intake on it, do a good tune up and get it propped right then leave it alone. The intake won't give much if any top end but it will give more torque and a little hp over the stock intake. That'll help you get up on plane quicker. The stock intake has horrible runners and flows like crap.

 

[knightowl]

Re: Upgrading mercruiser 350 v8 260 hp

First of all, thanks a bunch fella's for donating your time on this thread and sharing me your opinions of what could or shouldn't be done.

I think i will take some of your advice and drop my boat in hopefully tomorrow and do a fine test run with only me in the boat. I will run it WOT and see what RPM im getting. Seems to me i should be getting around 4,800? After that, i will come back to my prop guy and give him the info and of course YOU.

The elderbrock intake, could you please provide a link so i can search around for pricing with that part number? Depending on if its worth the money over improvement that is. My main concern is when someone is tubing or like 8-10 people in the boat i lose about 10 miles an hour EASY.

The current prop i got is a 4 blade made by Michigan 15" dia 16 pitch.

 

[HT32BSX115]

Re: Upgrading mercruiser 350 v8 260 hp

You can do a little prop calculating yourself when you know the specifics.

Go to http://www.go-fast.com/Prop_Slip_Calculator.htm

It can give you ball-park numbers.

If you go in with what you have: RPM, (GPS) speed, drive ratio, and prop pitch, it can tell you your slip. (which for a big boat like yours might be somewhere around 15-18%)

"play" with the numbers to determine what you should try in a different prop. I would also try a stainless steel 3 blade.

 

[knightowl]

Re: Upgrading mercruiser 350 v8 260 hp

Herd stainless isn't so good? When ever you go from forward to reverse, it has poor stopping? Like 2-3 second delay? Also if you hit a rock you will screw up your outdrive instead of bending or braking prop.

How do i find out my ratios of the out drive? Its a SE106 replacement drive of the mercruiser version. I believe my is a 1.47 UPPER (that's what it says on receipt and doesn't say anything for the bottom part. (receipt can barely be read, link fades over 1 year

 

[erikgreen]

Re: Upgrading mercruiser 350 v8 260 hp

The 1.47 drive ratio is normal for a v8, FYI.

The ratio only affects the upper, that's where the gears that affect this are. The lower is only gears for shifting and a right angle turn to the prop.

Erik

 

[n2ostroker]

Re: Upgrading mercruiser 350 v8 260 hp

The intake is an Edelrock p/n 2101 Performer non-EGR. That motor should have a quadrajet carb on it. You can usually pick them up for for $50-80 on Ebay or Craigslist. Then you'd need intake gaskets(~$8) and a carb gasket(~$7) and it takes a couple of hrs to change if you've never done one and/or the gaskets stick real bad.

I'd try a stainless prop. Something like a 14.25"-14.5"x 15p or 17p 3 blade. That should get the rpms up and give better bite.

 

[HT32BSX115]

Re: Upgrading mercruiser 350 v8 260 hp

Herd stainless isn't so good? When ever you go from forward to reverse, it has poor stopping? Like 2-3 second delay? Also if you hit a rock you will screw up your outdrive instead of bending or braking prop.

Poor stopping? I'm not sure what you're talking about.


Yes, if you drive it into a rock, there's the potential of damage to the drive but I know of Alphas that have hit rocks and logs with aluminum props that completely trashed the drive and required rebuilds.

Adding performance "stuff" like manifolds and carbs will probably improve performance in a small runabout.... but I think the only way you'll appreciably increase your performance that huge boat will be to add another 100 cu-in with the additional torque available.

 

[n2ostroker]

Re: Upgrading mercruiser 350 v8 260 hp

Meant to add about the prop to look for something that gives some stern lift. You're not going to get a ton of top end, you need something to get going and on plane so a prop with a bunch of bow lift won't help. The 4 blades will help but something like the 15'x16p you have is too big and giving you too much blade area making things worse.

 

[knightowl]

Re: Upgrading mercruiser 350 v8 260 hp

The intake is an Edelrock p/n 2101 Performer non-EGR. That motor should have a quadrajet carb on it. You can usually pick them up for for $50-80 on Ebay or Craigslist. Then you'd need intake gaskets(~$8) and a carb gasket(~$7) and it takes a couple of hrs to change if you've never done one and/or the gaskets stick real bad.

I'd try a stainless prop. Something like a 14.25"-14.5"x 15p or 17p 3 blade. That should get the rpms up and give better bite.

So look like you can pick up edelbrock 2101 Performer intakes for around $110 all day on ebay brand new. I am sure i can find them locally for around that price too so i wouldnt have to pay shipping. So you really think this might add some noticeable horespower? worth the time to replace and lets say worse case $150 dollar in spending?

As for quadrajet carb, i have a rebuilt one setting in a box. I had the dealership rebuild it and i ran it once or twice and removed it and bought a 1409 marine auto choke carb instead. I personally didnt like the quadrajet carb. I spent $250 on repair to the dealer on it and its the worse investment on my part that i have done as long as i can remember. The 1409 auto choke just seems like a perfect match for this engine. It has trouble starting on cold (gotta give it a couple of extra pumps of gas before starting) then once it catches, it works like a champ. Usually when i start my boat on cold, i pump it like 2-3 times, give it a crank, the engine catches the fuel and runs for about 2-3 seconds and dies. Then i do the same thing again and usually it either dies after 2-3 seconds or runs... or on the 3rd attempt it runs....... Keep in mind, all i did to the carb was pull it out of the box and drop it in the boat. I don't mind the extra cranking on cold but i think its because she idle's very low (about 700) (instead of 750) which i don't mind because it makes it easier to dock because engine is giving minimum power to the prop as it can, any lower and it would bug down and die.

 

[HT32BSX115]

Re: Upgrading mercruiser 350 v8 260 hp

The current prop i got is a 4 blade made by Michigan 15" dia 16 pitch. ................. I believe my is a 1.47 UPPER......

Using those numbers, You would get 42mph with 15%(optimistic) slip.

It would probably take far more than the ~230 propshaft HP you're developing to get that speed too.

Try putting a SS 14p prop on it and see what you get at WOT.


Another difference with SS vs aluminum is blade flex.


When my brother owned my 87 211 Liberator It had a 460 (340hp crankshaft) King Cobra installed. He tried a 21 pitch 3 blade aluminum prop and it would barely get up on a plane.

Most prop shop suggest SS for better performance....

 

[n2ostroker]

Re: Upgrading mercruiser 350 v8 260 hp

Stay with the Edelbrock carb. Big improvement over the q-jet. Since you have the square bore carb go with the Edelbrock # 2701. That is the square bore manifold instead of the spreadbore for the qjet.
As for making a big improvement? I don't think it'll be huge. It should give a bit more punch down low and a few hp up top. I think it would help you get on plane but it probably won't give you more than 1-2mph up top if that. You might look into getting the calibration kit for the carb and richen up the secondary rods on the carb and play with the springs to find the right combo. Also try different positions on the accel pump rod. They come set up for a 4.3 out of the box and sometimes have a lean spot off idle and when punching the throttle down.

I would definitely look to a stainless prop on that big boat. I think aluminum would be flexing to much causing some problems.

 

[knightowl]

Re: Upgrading mercruiser 350 v8 260 hp

Using those numbers, You would get 42mph with 15%(optimistic) slip.

It would probably take far more than the ~230 propshaft HP you're developing to get that speed too.

Try putting a SS 14p prop on it and see what you get at WOT.


Another difference with SS vs aluminum is blade flex.


When my brother owned my 87 211 Liberator It had a 460 (340hp crankshaft) King Cobra installed. He tried a 21 pitch 3 blade aluminum prop and it would barely get up on a plane.

Most prop shop suggest SS for better performance....

3 blade or 4 blade? 15" or 14" dia with 14 pitch? SS

 

[HT32BSX115]

Re: Upgrading mercruiser 350 v8 260 hp

If you're running a 16p 4 blade right now and you can find a prop shop that will let you try one, I would try a 15p 3 blade first (since that might be an "on-the-shelf" prop. If it still doesn't turn up then you might try a 13p 3 blade.


For diameter, I don't what will go on an Alpha. If a 15" dia 15-pitch would fit, try it......

I also think you should have a 1.66:1 or lower ratio (1.81 or more) drive......but you have what you have... You'll have to change props to change "gear". Right now it looks like you're running in "Overdrive"


That 16p 4 blade might be just great with that ratio if you had tricked 383 or a 454.


Prop selection is 60% calculation (prop-slip, prop selection tool etc) and 40% trial and error.

 

[fabrimacator21]

Re: Upgrading mercruiser 350 v8 260 hp

Stick with what you have and save your money for later. If you go adding heads you'll need to change exhaust manifolds too to a newer style and better flowing. Then you'll need to adapt that to your existing exaust. Then a carb or at least a jetting change and an intake manifold. The list goes on....... Then you're still stuck with a 350 in a large boat. No matter how you cut it you'll be lacking the torque needed to really get it up and going.

Going with the Vortec stuff would be a huge improvement if you wnated something to last till an upgrade to a bigger motor. It would give a fairly large torque increase and quite a bit of hp and as mentioned be dead reliable.

I would put an Edelbrock Performer intake on it, do a good tune up and get it propped right then leave it alone. The intake won't give much if any top end but it will give more torque and a little hp over the stock intake. That'll help you get up on plane quicker. The stock intake has horrible runners and flows like crap.

Why would he need to change exhaust manifolds? Stock vortecs are a 40hp improvent when stock manifolds are used on a truck... don't see how it'd be any different with boat manifolds...

Stock vortecs being a 40hp gain those RHS heads should be good for 50hp (larger valves and better flow) and won't require anything but swapping the heads as they'll accept older intake manifolds. Put a decent Air-Gap intake manifold on it and you'll be right around 310-320hp which seems like thats all you'd want to do with the alpha drive. Depending on how many cfm your carb is you may not need a different carb or jetting. To sum up you don't need different exhaust manifolds or even a different intake. If you wanted to you could just throw those heads on there and go. You may need some different carb jetting though.

Theoritically speaking that would be another 5-6 mph.

Theres ways to get that number higher but it just depends on how hard you want to push that alpha drive.

As for props, I know the turning point aluminum props are supposed to be as good as it gets for aluminum props... they are modeled after SS props.



Also why are you spending so much time at the dealer? Do you like being ripped off?

250 bucks for carb rebuild? Could have bought a new one for that.

 

[n2ostroker]

Re: Upgrading mercruiser 350 v8 260 hp

Why would he need to change exhaust manifolds? Stock vortecs are a 40hp improvent when stock manifolds are used on a truck... don't see how it'd be any different with boat manifolds...

Stock vortecs being a 40hp gain those RHS heads should be good for 50hp (larger valves and better flow) and won't require anything but swapping the heads as they'll accept older intake manifolds. Put a decent Air-Gap intake manifold on it and you'll be right around 310-320hp which seems like thats all you'd want to do with the alpha drive. Depending on how many cfm your carb is you may not need a different carb or jetting. To sum up you don't need different exhaust manifolds or even a different intake. If you wanted to you could just throw those heads on there and go. You may need some different carb jetting though.

Theoritically speaking that would be another 5-6 mph.

Theres ways to get that number higher but it just depends on how hard you want to push that alpha drive.

As for props, I know the turning point aluminum props are supposed to be as good as it gets for aluminum props... they are modeled after SS props.



Also why are you spending so much time at the dealer? Do you like being ripped off?

250 bucks for carb rebuild? Could have bought a new one for that.

Not to open a can of worms but....

You can bolt on all the numbers you want.....
While your at it I hear stickers make things faster too.

Bolt on the Vortecs and use a stock intake?? What would be the use?

He has old style log manifolds. That would be like sticking a plug on the exhaust port of those heads. The power he picked up would be great down low. The 30-40hp your speaking of wouldn't happen because it comes higher in the rpms where his exhaust would act like a restrictor plate.

The carb is fine just get the calibration kit. It makes tuning things like holeshot and throttle changes much easier.

Changing heads isn't just a bolt on a and go process. You have tear down, cleaning, gaskets, fasteners, valvetrain parts, maybe necessary intake manifold and valvecovers. Trust me IF you were to buy the RHS heads which won't be some magical bolt on hp for $500 it'll cost you double or more by the time your done. Thats assuming everything goes as it should.

As for the Turning point props. Don't do it. I own a 23p Hustler and while it will make a great back up prop it isn't meant for heavy boats or higher torque/hp. It does flex and create slip on my boat which is about half the weight of yours. I can spin it going from a cruise to full throttle. Big boat = stainless prop if you expect any kind of performance.

Save your money for a big upgrade later if you decide to hang on to the boat for a few yrs. Tune what you have and get the most out of it then make a decision on what you can do later.