Big Block Question

[HT32BSX115]

Re: Big Block Question

Howdy,

When I was delusional and wanted to stay with the 460 King Kobra I had in my Liberator, I had these grand ideas of really tricking out the 460 (rated stock at 340hp crank)

I was hanging out on the "Offshoreonly" site and ran across a thread that discussed how much HP a 1.43:1 King Cobra drive would handle.

There was a guy on there that had a 211 Liberator with the KC drive that had built up a 540 cu in stroked "460" engine that was severely tricked out in many ways.

I don't remember the claimed HP but he said he could "Bury the speedometer at 80 mph" and not break the drive. I personally think the 211 Lib would be very dangerous at that speed.

Mine did 60 with the 460 KC and now does 57(GPS) with my '97 454/Bravo III, [Mercruiser rated @300 prop HP] (4600rpm, 1.81 drive, 26p props)

I would like to do the same thing (switch to a 502) but I am sort of skeptical that I would get a large increase in speed though. I am guessing I would have to go to 28 or 30p props if the increased HP was going to make the big difference...


Please post any results you get when you actually do the switch.

A lot of people here would probably love to see the Before & After data.



Cheers,


Rick

 

[tinman565]

Re: Big Block Question

I'll be happy to post results...I'll even tell you EXACTLY what we did, prop size, and any other important information. You guys help me out enough, its the least I could do. I check in here frequently..so if anybody wants to talk about this, send me a message.

 

[tinman565]

Re: Big Block Question

Can anybody tell me for sure if I have a Gen 5 or Gen 6 motor ? Tell tale signs on the block or motor ? I think 1991 was the transition year for them, so it could be either one. It has an aluminum intake..a q-jet carb...a forged crank.. had a mechanical fuel pump...and has a steel timing chain cover. Any other ideas ? Thanks.

 

[Don S]

Re: Big Block Question

Mercruiser started using the Gen V in 92, and it didn't have a mechanical fuel pump pad on the block.
They didn't start using the Gen VI until 96.

 

[tinman565]

Re: Big Block Question

So your telling me I may have a Gen 4 ? Or do I possibly have the date of the motor wrong ? Is there anyway to ID the motor using block numbers, or head numbers ? Grrrrrrrrrrrrrrrrrr !!!!!!!!! lol

 

[Don S]

Re: Big Block Question

Do you have a Mercruiser SN? There should be a tag just above the starter on the edge of the block where the flywheel cover attaches.
Any cast block numbers could help also. http://www.mortec.com/location.htm

 

[HT32BSX115]

Re: Big Block Question

Do you know what the engine serial number is? (I can't remember if you posted it earlier)

Mine is a 97 7.4L engine and it's a GEN VI

I also didn't mention it before but my Lib with the similarly powered OMC, while a few mph faster, was a REAL DOG out of the hole....(I did a little reading on Offshoreonly.com and found a few threads that indicated that the CC 245 was a little slow in the hole shot too with a 454/Bravo I)

Now, with the Bravo III it just ROCKETS out of the hole but is about 3 MPH slower..... (Ill take holeshot over speed any day I guess)

You might consider a Bravo III lower if you want it to be quick out of the hole..... (Your drive ratio may be all wrong though)

 

[tinman565]

Re: Big Block Question

Thanks for the link. I found the tag, looked up the number ( 0D398374 ), and if I read it right..lol..I believe its a 502 Mag Bravo (whatever that means). Thanks Don..at least now I can start looking for the correct parts.


502 Mag. Bravo GM 502 V-8 1990-1992 0C878221-0D824588
502 Mag. Bravo Gen. V GM 502 V-8 1992-1993 0D824589-0F114528
502 EFI Gen. V GM 502 V-8 1993-1995 0D840650-0F802599

 

[Don S]

Re: Big Block Question

It's a 1990 motor. Merc model number 4502110CS

I believe its a 502 Mag Bravo (whatever that means).

It just means the motors accessories are designed for a Bravo sterndrive as compared to an MIE, which is a straight inboard, not sterndrive.

 

[tinman565]

Re: Big Block Question

Is there a link..or site that I can go to, to find out specifics about THAT motor ? What heads were on it...exactly what cam is in it...and any other specifics about that motor ? Thanks. (as you can see..I'm doing my homework)

 

[HT32BSX115]

Re: Big Block Question

Doug Russell (as well as any site that has an online parts lookup tool) shows all the Mercury part numbers....... 0C878221 THRU 0D824588 , But I'm not sure that helps you determine what the specs of the cam is.

You could go to Crane Cams, or other after market cam grinder/manufacturer and buy an excellent marine grind cam for that engine. They know exactly what you need for a submerged or dry exhaust (Inboard, I/O , or jet) application and what will work best for each.....

 

[Don S]

Re: Big Block Question

You can get a lot of information on the engine from the OEM service manual, just go up to the Adults only sticky at the top of this forum and go to the service manual links, you want manual #15.

 

[tinman565]

Re: Big Block Question

Don...I'm gonna buy you a beer someday sir. Thanks.

 

[tinman565]

Re: Big Block Question

Don..I tried to download that file twice ( #15 ), and it took awhile..then it said the file was damaged and could not be repaired. What now ?

 

[Don S]

Re: Big Block Question

Instead of trying to open it, RIGHT click the link and choose "Save Target As" and save it to your desk top directly. Is your Adobe Acrobat reader up to date?