1988 Merc 7.4 Oval Port?

[Sorrento 25]

Is this an oval port or rectangular port engine? When did Merc switch over to rectangular port heads?

Edit: I just found this searching on the net ->

The 454/Alpha combo was only available for one year, 1987, then promptly discontinued. It just was not designed to handle the torque of the 454, (and that was the entry level 330 hp model) another point of confusion is the 1987 454 Magnum was just a 330 hp cast crank, cast piston, oval port head motor. The 1988 Magnum was the real deal, forged pistons, crank, rectangle port heads and high rise aluminum intake.

Is there a "regular" 454 and a "Magnum" 454? Mine is an '88 with an Alpha - was the alpha used behind the 454 for two years and the info above is incorrect?

How can I identify if I have the better 454 or not?

 

[Don S]

Re: 1988 Merc 7.4 Oval Port?

The 454 Alpha was used from 86 thru 88, which was the 330hp IO engines.
I scanned this chart from the Mercruiser service manual #9.
All you have to do is look at the intake manifold. If the passages going to the head are round then the ports are round.

 

[Sorrento 25]

Re: 1988 Merc 7.4 Oval Port?

Thanks Don I guess its the lame-duck version that I have.

 

[Don S]

Re: 1988 Merc 7.4 Oval Port?

Be thankful you don't have the bigger/badder engine, the Alpha drives are only rated for 300hp and they don't handle the torque of the 330hp 454 if you get heavy handed on the throttle all the time either. That's why in 88 they (Mercruiser) came out with the Bravo drive. Something that could handle the torque and HP of a big block.

 

[Sorrento 25]

Re: 1988 Merc 7.4 Oval Port?

Yes that is one of my concerns. I'm installing a full water pump, synthetic lube, and a drive shower this winter.

How do you think a 383MPI/Bravo 1 would compare to this current engine? Fairly equal or noticeably better performance?

 

[Don S]

Re: 1988 Merc 7.4 Oval Port?

The 6.2 with a B1 would be about the same speed, out of the hole etc. Only you would get better milage for your fuel dollars with the MPI and the B1 would last where the A1 won't
Now, if you want to make that boat something else, quicker out of the hole, better milage than the 6.2 Merc, better low speed control and higher top end, try one of these in the link below. And NO, the Bravo 3 wouldn't help.

http://www.volvo.com/NR/rdonlyres/0D107FBD-ED1C-44E6-847F-2C5336A85BED/0/57_DPS_07.pdf

 

[Sorrento 25]

Re: 1988 Merc 7.4 Oval Port?

It definitely appears to be the best stern drive out there based on my quick little search (no vibration and no heat), but its $2800 more money than the 383 MPI too.

 

[Reel Poor]

Re: 1988 Merc 7.4 Oval Port?

Ya get what ya pay for. With a little shopping around the prices get pretty close together.

 

[degree]

Re: 1988 Merc 7.4 Oval Port?

I also have the 330 Mercruiser/Alpha combo.:% I've been warned by just about everybody to be easy on the drives due to their inability to handle the torque.

Needless to say, I'm already saving my 'pennies' for a pair of Bravos I can install, particularly since I intend to install TPI :devil:

 

[Bondo]

Re: 1988 Merc 7.4 Oval Port?

Needless to say, I'm already saving my 'pennies' for a pair of Bravos I can install, particularly since I intend to install TPI :devil:

you Do realize that you're talking about 2 Complete Repower Packages,............

There'll be Little or Nothing that can easily be Reused with That Swap...........

My Guess is that'll run you about $30,000.00....... Plus........
Depending on whether You do any of the Labor...........

 

[Don S]

Re: 1988 Merc 7.4 Oval Port?

Hey Bondo, there is a lot he can reuse, well maybe not a lot. Lets see, the Bravo transom shield uses the same transom cutout as the Alpha, The shift and throttle cable from the helm will be the same, oh yeah, the fuel line from the tank to the engine can be reused

 

[Bondo]

Re: 1988 Merc 7.4 Oval Port?

Ayuh,..............

OK,........ So, Deduct a $ Buck, 2.98 from My Estimate.......d

 

[Reel Poor]

Re: 1988 Merc 7.4 Oval Port?

You guys are real heartbreakers. :'(

 

[degree]

Re: 1988 Merc 7.4 Oval Port?

Ahhhh, go ahead! Pour cold water over my head! See if I care!d

Actually, I can probably pull the conversion off for about 10K as I will be doing most of the work, including running a return line to the fuel tank.

My newbie introduction elsewhere mentioned that I'm an old gearhead, having built street rods, street machines, circle-track racers and dragsters. Very little in the way of mechanicals intimidates me. In that way, I'm lucky, I guess...

 

[Bondo]

Re: 1988 Merc 7.4 Oval Port?

Ahhhh, go ahead! Pour cold water over my head! See if I care!d

Actually, I can probably pull the conversion off for about 10K as I will be doing most of the work, including running a return line to the fuel tank.

My newbie introduction elsewhere mentioned that I'm an old gearhead, having built street rods, street machines, circle-track racers and dragsters. Very little in the way of mechanicals intimidates me. In that way, I'm lucky, I guess...

I must have Missed that,....... Anyways,........
Welcome Aboard,......It's Always Great to meet another Old Gearhead,........

As you may have noticed,.......
Don is a Mercruiser Technician,.....
He's a By the Book fella.......

I'm just an ole Common Sense Mechanic,........
I build things that Shouldn't be built, with Parts that Shouldn't fit......
I consider myself a King of Creative Engineering,......
After All,..... I don't think I own ANYTHING that I haven't made Easier to Service, or just Run Better......
'ell,....... I haven't found Anything that couldn't use alittle Tweeking.....
Nor, Anything I Can't Do,......d

Btw,...... I think that $10,000. is Still just on the edge of Optimistic,.........
Even using old Junk Parts like I do.......

 

[Don S]

Re: 1988 Merc 7.4 Oval Port?

As you may have noticed,.......
Don is a Mercruiser Technician,.....
He's a By the Book fella.......

Yeah, I pretty much give info "By The Book" mostly because it can be verified using the book and it's known to work on these engines they are asking about.

I have seen way too many mistakes made on marine engines because it was done by an auto mechanic that didn't even know there was any difference. The other thing is most of the posts here have to do with common mechanical problems that any marine mechanic or even an auto mechanic could figure out easily.

Bondo has been having fun with old Mercruiser stuff for a long time and understands what will and won't fit when making changes. And I would bet it was mostly by trial and error (heavy on the error side), right bondo? ? ? ?
I am also with you on the 10K being optimistic. You have to buy a lot of GOOD used parts at really good prices to get under 10K when upgrading from Alpha's to Bravo with twins.

PS: My favorite car is the one I built in 66, it was a 56 Chevy with a 327, dual AFB's w/ dual point ignition, 4spd tranny, Pefect black exterior, perfect red rolled & pleated buckets............................. Waaaaaa, I want it back so bad!

 

[mkast]

Re: 1988 Merc 7.4 Oval Port?

Email me, I'm running the same power package.

 

[Fishermark]

Re: 1988 Merc 7.4 Oval Port?

Hey Don,
Just so you can reminisce a little now that it must be getting cold there in Alaska - here is my current ride - and has been for the last 30 years!

 

[Bondo]

Re: 1988 Merc 7.4 Oval Port?

My favorite car is the one I built in 66, it was a 56 Chevy with a 327, dual AFB's w/ dual point ignition, 4spd tranny, Pefect black exterior, perfect red rolled & pleated buckets............................. Waaaaaa, I want it back so bad!

Ayuh,..........

You Really Are an Old Fart,..??.... Aren't you,..........dd

Back in 1966,..........
I was Still building AMT Models of Those Cars,+ Modifying my Tonka Trucks...............

Beautiful Sedan ya got there Fishermark..................

 

[Sorrento 25]

Re: 1988 Merc 7.4 Oval Port?

I'm an old gearhead too, but the problem I have with wrenching on the boat is climbing in and out. It seems I can't work for 10 minutes straight before I have to climb out and grab something else from the garage. Eh, the exercise sure won't hurt me.

My favorite car was my 69 Dart Swinger. I stripped that to a bare uni-body and replated every nut, bolt and screw on it. The bottom was as nice as the top. Sold it for the house down-payment in the late 90s when the cars weren't worth much.

If this Alpha does hatch on me I want a repower plan for 2008. I have one spare Alpha here to rebuild for a backup already.

I'd consider a Bravo upgrade with some heads, cam, etc. but if I don't have the forged 4-bolt bottom end its not worth it.