Mercruiser OEM to performance????

[Howard Sterndrive]

Re: Mercruiser OEM to performance????

I have to disagree, Howard. I made several changes over the years to my once stock 1984 260 hp 5.7; alum hi rise intake, alum heads, cam, roller rockers, ss headers.

interesting.

was the engine making its full 260Hp before the swapping though?

 

[Philster]

Re: Mercruiser OEM to performance????

There are ways to deal with reversion... depending on what your exhaust manifolds look like, you can for example weld extensions onto the inner tube of the risers to more the point back wher ethe water is mixed with the exhaust. Also it's important to realize that reversion is a funny thing and not always so predictable just by looking at cam duration. to be safe, if you add much duration, you have to check once you get it running.

I'm not a ford guy, so I can't comment too much on specifics here, but I do humbly, respectfully disagree with the folks who say it's not worth doing. or that if you make more power you'll kill the bottom end. My experience is that if you pay close attention to what you're doing, do the homework and design the build so it has a nice flat torque curve, you can get great results!


Cheers!

http://www.youtube.com/watch?v=EHoXsQc6644

Yes, it's possible to make power that has a marine-applicable power band.

They key is to be forewarned and, as you say, to pay close attention.

 

[rbezdon]

Re: Mercruiser OEM to performance????

18WCMerc - Be careful to choose a 4bbl Marine Rated. It has a different configuration to help prevent fuel vapor from escaping into the closed engine compartment of a boat. As Bondo stated earlier any part which touched fuel or electrical will have a marine rating. On the issue of the Aluminum Intake, fine for closed cooling syatems and freash water but DONT use it if you are going to run in salt water. I found thisd out when I converted my Chevy 350 from stock cast iron to an Aluminum Eddelebrock Performer series. Good Luck and have fun.

 

[18WCmerc]

Re: Mercruiser OEM to performance????

lol i noticed that info was a little...off to say the least. but as a newb ive already learned to pick my battles carefully around here.

 

[Philster]

Re: Mercruiser OEM to performance????

Well.... just keep in mind that when the Mercs and Volvos of the world try to solve power issues, they move up in cubic inches, and wind up with stump-puller engines by their inherent design (displacement, V8, undersquare). 8.2 Liters in the common performance boats: Naturally aspirated, 8.2 liters, 502 cubic inches, running mild cams (considering these are performance boats), and basic intakes.

It's how they solve power issues.

When they want more power, the go the supercharger route on the biggest block available (502), a solution that is famous for delivering boost at low RPM.

I think, from a performance standpoint, getting more juice out of an engine AND maintaining a character, power curve and keeping the use-ability factor for a marine application is indeed a challenge.

Good luck!

 

[HT32BSX115]

Re: Mercruiser OEM to performance????

well, guess what... boat engines NEVER turn that fast.

Yeah..... it's probably best to NEVER say NEVER........ (??)


Go over to to the "Offshoreonly" forum and you'll find all kinds of "Go Fast" boats.......

Many are turning 5000 to 6000 RPM with stock Alphas, Bravos, there were a few stroked 460 King Cobras, and other HUGE cu-in BBF's etc etc etc....

drive showers required of course...........Mercury doesn't recommend it but it's happening just the same.....


These are not engines and drives that are going to last for ever but you really cannot say that marine engines NEVER turn over 4600, 5000 or even 5500 etc.....

And there's a LOT of jetbotes out there that are running upwards of 6000 RPM++ ....... With dry-stacks there's no such thing as reversion!!


Your mileage may vary.....



Cheers,


Rick

 

[JetBote]

Re: Mercruiser OEM to performance????

EDIT: It is possible to disagree with someone without insulting them

If your engine is turning 4200rpm, your gimble inner race is turning 4200. The outside is stationary. For most bearings, it takes 600 revolutions to make the actual bearings inside to make one revolution. So, at 4200, the rollers make 7 revs in a minute. If you added that much power, and got your engine to 5200, it now spins 8.6 times in that minute. Hardly catastrophic as far as increase goes. Even if it were 50 shaft revs per one bearing rev, the difference would be 20 rpm. If you overgrease a bearing, it actually adds drag and creates more heat.

Now, if you are looking to add power, you won't notice jack on 20 horsepower here, and 10 there. To make a boat really benefit from changes, takes bigger steps. Going to a 4 bbl carb, is really only adding more air, not that much more fuel. That's fine to add the carb, but it's useless if you can't get that added air to flow out of the engine. Mainly speaking, the exhaust, and heads need to be able to let the air flow out. Read up on VE, volumetric efficiency.

About adding power, your failure will come from the outdrive shafts. They don't like a whole lot of torque than what they were built for. You'll find they live longer when you roll into the throttle if you have a stronger engine and a stock drive. You can't drop a V8 into a stock Suzuki Samurai and expect it to last, you'll want the Ford 9".

 

[JetBote]

Re: Mercruiser OEM to performance????

Taping from my boat, you'll hear 6000

http://www.youtube.com/watch?v=TuJenkZTdMY&feature=youtube_gdata_player

 

[45Auto]

Re: Mercruiser OEM to performance????

For most bearings, it takes 600 revolutions to make the actual bearings inside to make one revolution. So, at 4200, the rollers make 7 revs in a minute.

Interesting theory there. Any references?

The Ball Spin Frequency is the rotation rate of the balls or rollers. The surface of the ball or roller is rotating at the same speed as the outer surface of the inner race (unless the roller is skidding, which means your bearing will shortly die). Since the diameter of the roller is much smaller than the outer diameter of the inner race, the roller has to be rotating faster than the inner race to keep the surfaces moving at the same speed. Since the outer race is fixed, half of the rotational speed goes into moving the roller around the outer race.

We use Bearing Frequency Analysis to analyze the condition of bearings by sound. The different speeds of the inner race, outer race, rollers, and carrier give off characteristic sounds at specific frequencies if they're damaged. You can calculate the frequency, thus RPM, of the rollers (Ball Spin Frequency) from the formula here

http://www.dliengineering.com/vibman/gloss_bearingtones1.htm

or in the Plant Engineer's Notebook on page 44/804:

http://books.google.com/books?id=9Y...esnum=7&ved=0CDYQ6AEwBjgK#v=onepage&q&f=false

Using a pitch diameter of 3.5" and a ball diameter of .375" (going from memory, don't have a gimbal bearing in front of me) gives a roller spin rate of around 20,000 RPM with the inner race turning at 4200 RPM.

 

[wca_tim]

Re: Mercruiser OEM to performance????

just to put in perspective...

the 385 ci small block in my little boat: competition ported afr195 heads with 2.05 intake and 1.625 exhaust valves, comp hydrajulic cam with 226/236 duration, comp cams roller rockers, hardened one piece pushrods, dished forged blower pistons, H beam rods, steel crank, bluprinted and balanced, zero-decked and set up with a .040 quench, edelbrock airgap RPM intake, holley 750 double pumper with a proform body and Quickfuel base, 7 quart oil pan, stock oil pump, stock fuel pump, IMCO powerflow exhaust manifolds with long risers, oversized oil cooler from a big block set up with a 190 degree thermostat, running remote wix filters, Stock thunderbolt ignition with a v6 module, 14 degrees advance all in by 2500 rpms, 30-32 degrees total timing, free flowing gaffrig flam arrestor.

We didn't dyno the current configuration, but is pretty safely around 450 peak horsepower with a fairly flat torque curve. I gaurantee if you drove it you wouldn't think that the free flowing heads, intake and carb (that carb is really flowing a good bit more than 750 cfm, it really just has holley metering blocks and float bowls on it), free flowing exhaust, etc... limits the torque. I can have 4 people in the boat and pull anyone out of the water on a slalom ski with half throttle... with more throttle and the drive trimmed out just a little bit, it'll about stand up on end

I've run several drives and gear ratios and switch back and forth depending on what I'm using it for: an allpha one ss drive or a stock alpha drive. I run redline shockproof heavy gear lube and no drive shower and am not afraid to run flat out with either drive. I make sure NOT to shift into gear above 600 rpms (for alpha drive, can chip a gear and creat a weak spot to have the gearbox come unglued when running hard), and I am careful not to catch air with the hammer down. other than that I run it hard - why spend the considerable time and expense if you're not going to put what you build to use... ;-)

I've held it at 5500 rpms for a half hour or more and routinely run at 400- 4500, even 5000 rpms for miles and miles on end... it's also seen 6000 rpms more than a few times. not a bobble... (knock on wood)


the point? build what you want, search on here and oher places, pay attention to what components you use and it's very possible to wimd up with something that has good manners, will hold together and has some serious pucker factor when you put the hammer down. btw. the posts that 45auto put up on reversion are about the best out there on the web... dead on.

Good Luck with your project! I'll look forward to reading about it!

ps / addition: THE TECHS AT COMP CAMS (AND PROBABLY MOST OTHERS) DON'T KNOW SPIT ABOUT MARINE ENGINE CONSIDERATIONS!


definately not a professional vid, but where we are... ;-)

http://www.youtube.com/watch?v=EHoXsQc6644

 

[Howard Sterndrive]

Re: Mercruiser OEM to performance????

you have no idea what you're talking about and you're spewing crap when it comes to performance and boating. Stick with the canoe stuff.

sorry if I insulted someone's K&N?
Cool boat, btw.

 

[wca_tim]

Re: Mercruiser OEM to performance????

sorry if I insulted someone's K&N?
Cool boat, btw.

Nicely done edit! ;-)

 

[45Auto]

Re: Mercruiser OEM to performance????

If I wanted to hotrod a boat (I'm lazy, my way to get the performace I wanted was just to buy the biggest engine I could in the smallest boat they put it in) the VERY first thing I would do is become very good friends with WCA_Tim. If you're smart, you'll search all his posts for info and contact him. I didn't think he was still around, haven't noticed him posting lately.

Based on his previous posts over the last couple of years he's one of the very few people that are knowledgeable of the demands on a boat engine, understands the basics of how engines work and how that is related to performance improvement, and is capable of making logical analytical decisions about the necessary performance tradeoffs to maximize his boat's performance relatively cheaply.

If I remember correctly, he's taken his small block boat from around a 50 MPH top speed to almost 90 MPH over the last couple of years. No magic, everything he's done makes sense.

I personally plan to be standing on his doorstep if I ever decide to hotrod a boat! A few roundtrip plane tickets to pick his brains would be MUCH cheaper than the stuff I'd destroy trying to learn what he's done!

 

[Howard Sterndrive]

Re: Mercruiser OEM to performance????

Nicely done edit! ;-)

My chips are Navionics, not shoulder mounted.

I wouldn't turn a 30 year old pre alpha drive at the rpm's you guys are suggesting, but hey... the OP is a big boy and he can take that advice if he wishes. If you guys are spinning MC1 drives at 6K, that's excellent.
I figured if $30 for points was a big investment, that ported heads aren't wise. Maybe I'm thinking too many steps ahead and taking all the fun out of the discussion.
Where is that canoe forum?

 

[Aloysius]

Re: Mercruiser OEM to performance????

Just rebuilt 2-302's. Heads had already been swapped for 351 air injection heads, which suck. Marine cams use the 351 firing order, but are lumpier than street 351. Torque peak around 3200 rpms, installed straight up.

Heads were pocket ported..4bbl intake (stock) was "massaged". Stock 302 marine uses 450 cfm Holley, which is more than adequate for 4500 rpms.

Those engines are bone stock production blocks.

Many Fords use a Prestolite distributor. since I rebuild/curve distributors, I'll say the Prestolites are more than adequate for these engines. I run 36 degrees advance, all in at 2800 rpms.

My observation about K&N vs. stock flame arrestor..added 200 rpms with the K&N. Stock arrestors are lousy at full throttle, but at cruise you'll never notice a difference.

I have clearance problems, but I'd love to have a good aluminum medium rise manifold instead of the really squatty factory unit.

 

[JetBote]

Re: Mercruiser OEM to performance????

Interesting theory there. Any references?

The Ball Spin Frequency is the rotation rate of the balls or rollers. The surface of the ball or roller is rotating at the same speed as the outer surface of the inner race (unless the roller is skidding, which means your bearing will shortly die). Since the diameter of the roller is much smaller than the outer diameter of the inner race, the roller has to be rotating faster than the inner race to keep the surfaces moving at the same speed. Since the outer race is fixed, half of the rotational speed goes into moving the roller around the outer race.

We use Bearing Frequency Analysis to analyze the condition of bearings by sound. The different speeds of the inner race, outer race, rollers, and carrier give off characteristic sounds at specific frequencies if they're damaged. You can calculate the frequency, thus RPM, of the rollers (Ball Spin Frequency) from the formula here

http://www.dliengineering.com/vibman/gloss_bearingtones1.htm

or in the Plant Engineer's Notebook on page 44/804:

http://books.google.com/books?id=9Y...esnum=7&ved=0CDYQ6AEwBjgK#v=onepage&q&f=false

Using a pitch diameter of 3.5" and a ball diameter of .375" (going from memory, don't have a gimbal bearing in front of me) gives a roller spin rate of around 20,000 RPM with the inner race turning at 4200 RPM.

My primary example numbers come from the number of rotations of a tire in a one mile distence. The tire would make app 600 revs per mile, and the bearing would make one rev, give or take, in that mile. I couldn't quote or find it if I wanted to. But, given your obvious knowledge of bearings, can you really say that an increased engine speed of 1000 rpm is really going to have a catastrophic impact on a gimble bearing as suggested by Howie?

 

[wire2]

Re: Mercruiser OEM to performance????

interesting.

was the engine making its full 260Hp before the swapping though?

Well, that's difficult to say, since I have never taken the time to do a dyno test. Coulda, shoulda but didna.

It was brand new in '84, and after break-in it maxed out at ~54 mph @ 4900 rpm with the 21" ss prop. It came up on plane fairly quick but as I recall, it took 3-4 seconds. The mods came 1 at a time over the years since '84.
A big plus about losing the iron intake, heads, exhaust, was that I also lost 200 lbs of weight.

And with building my own double wall ss headers, I added some extra length to the inner shell after the riser portion, which allowed me to run a mild cam without reversion concerns.

 

[18WCmerc]

Re: Mercruiser OEM to performance????

tim, your 383 is TITS!!! i have built motors like this before in automotive applications for bracket racing. once i can make the infamous reverse eddie hill transformation, my webbcraft may get a nice engine or maybe another boat down the road. that was inspiring. your cam break in vid was cool. i remember those days of buring assembly lube off perf. parts. love the barely running idle too.

 

[wire2]

Re: Mercruiser OEM to performance????

My primary example numbers come from the number of rotations of a tire in a one mile distence. The tire would make app 600 revs per mile, and the bearing would make one rev, give or take, in that mile. .....

Ok, I think i figured out where you're coming from. You're alluding to the rotational travel of the balls around the race?
True, the ball will travel around the inner race much slower than the rpm of the shaft, (ignoring the actual rpm of the ball). The 600:1 seems extreme though.

If we use 45Auto's numbers of 3?" inner race and 3/8" roller dia, the race circumference is 3.1416 x 3.5 (?D) = 10.995"

The ball circumference is 1.178"

That gives a ratio of 9.333:1, or 450 rpm for the shaft's 4200.

It's not really a number of any significance in this thread.

 

[Philster]

Re: Mercruiser OEM to performance????

just to put in perspective...

the 385 ci small block in my little boat: competition ported afr195 heads with 2.05 intake and 1.625 exhaust valves, comp hydrajulic cam with 226/236 duration, comp cams roller rockers, hardened one piece pushrods, dished forged blower pistons, H beam rods, steel crank, bluprinted and balanced, zero-decked and set up with a .040 quench, edelbrock airgap RPM intake, holley 750 double pumper with a proform body and Quickfuel base, 7 quart oil pan, stock oil pump, stock fuel pump, IMCO powerflow exhaust manifolds with long risers, oversized oil cooler from a big block set up with a 190 degree thermostat, running remote wix filters, Stock thunderbolt ignition with a v6 module, 14 degrees advance all in by 2500 rpms, 30-32 degrees total timing, free flowing gaffrig flam arrestor.

We didn't dyno the current configuration, but is pretty safely around 450 peak horsepower with a fairly flat torque curve. I gaurantee if you drove it you wouldn't think that the free flowing heads, intake and carb (that carb is really flowing a good bit more than 750 cfm, it really just has holley metering blocks and float bowls on it), free flowing exhaust, etc... limits the torque. I can have 4 people in the boat and pull anyone out of the water on a slalom ski with half throttle... with more throttle and the drive trimmed out just a little bit, it'll about stand up on end

I've run several drives and gear ratios and switch back and forth depending on what I'm using it for: an allpha one ss drive or a stock alpha drive. I run redline shockproof heavy gear lube and no drive shower and am not afraid to run flat out with either drive. I make sure NOT to shift into gear above 600 rpms (for alpha drive, can chip a gear and creat a weak spot to have the gearbox come unglued when running hard), and I am careful not to catch air with the hammer down. other than that I run it hard - why spend the considerable time and expense if you're not going to put what you build to use... ;-)

I've held it at 5500 rpms for a half hour or more and routinely run at 400- 4500, even 5000 rpms for miles and miles on end... it's also seen 6000 rpms more than a few times. not a bobble... (knock on wood)


the point? build what you want, search on here and oher places, pay attention to what components you use and it's very possible to wimd up with something that has good manners, will hold together and has some serious pucker factor when you put the hammer down. btw. the posts that 45auto put up on reversion are about the best out there on the web... dead on.

Good Luck with your project! I'll look forward to reading about it!

ps / addition: THE TECHS AT COMP CAMS (AND PROBABLY MOST OTHERS) DON'T KNOW SPIT ABOUT MARINE ENGINE CONSIDERATIONS!


definately not a professional vid, but where we are... ;-)

http://www.youtube.com/watch?v=EHoXsQc6644

So... like you didn't just hang a couple of performance parts on 'er and call it a day?