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**Guest** · 06-02-2012, 08:51 AM

Dropping several hundred lbs is a good thing. The performance difference may be greater that you think, though- going from a 7.4 to a 5.0 is a huge change. The peak power ratings (330 for the big block, 260 for the 5.0) is max rated- you'll be losing the torque of the big block throughout the entire RPM range.

That being said, I loved the smoothness of the 5.0 MPI/B3 that was in my 2359.

**2850Bounty** · 06-02-2012, 09:22 AM

I think that the 5.0L, even while rated at 260 hp, is going to make this boat under-powered.

Here's something to consider.

With regard to the 5.0L 260 hp....... at what RPM this rating is taken???

Example:

When the 5.7L Vortec was introduced, it was rated at 315 +/- HP.

It's predecessor, the 5.7L, was at 260 HP.

The 5.7L Vortec was rated at 5,200/5,400 RPM.

We do not operate our engines at anywhere near 5,200/5,400 RPM.

Look at the 5.0L MPI specs.

I'd be willing to bet that the rating is at a much higher RPM than what you will be able to use.

This can be a common misnomer when they advertise the 5.0L @ 260 hp.

They've also given the 5.0L mpi 260 hp BIII the 2.2:1 ratio for a good reason! Less Torque!

With decent HP and Toruque:

The BIII drive performs best at above 40-45-ish MPH.

The Duo Prop performs best at speeds below 40-45-ish MPH.

The 2556 is not a 40-45-ish MPH boat.

This is not a derogatory statement. There are on-line test results that can be found that support the BIII -vs- Duo Prop testing.

The BIII will outperform the DP at the higher speeds noted.

The SBC idea is great, IMO...., just not in the 5.0L version. You need Torque, and lots of it!

Have you considered the 377/383 version SBC?

This engine could be used with your BII drive.

If could also be used with the Duo Prop drive.

Either renders a weight savings.

You say; "what i do want most of all is a safe and reliable boat not a speed boat."

Speed is not necessarily what we're after when we achieve more power and/or performance. However, there will be times when the added performance will pay dividends beyond speed alone.

Remember, performance is what gets these boats up and onto planing attitude...... and planing attitude is where we begin to see real cruising efficiency and economy.

The only other efficient speed is "hull speed", in which case you may as well install a 120 hp engine.

Given the charateristics of the 2556, I'd be more inclined to use the 377/383 with the 1.78:1 Duo Prop drive.

If you don't care for the Duo Prop idea...., then stick with your BII, and go with one of the 377/383's.

You could then re-sell the 5.0L MPI/BIII package.

.

**Guest** · 06-02-2012, 01:08 PM

I would personally not step back from a 7.4 to. 5.0, even carbed to mpi. With the right tuneing and prop that 7.4 should keep that boat at a comfortable cruise speed while barely working.

**Guest** · 06-02-2012, 07:47 PM

half the guys out there with there 28 30ft boat have a 7.4 driving them an you say not to step back on a 25 ft boat how about all the blokes out there with 2556's and omc drives and volvo's please do you guys have any thoughts

**Guest** · 06-02-2012, 10:25 PM

i have the 2560 with a mpi 350 and volvo duo prop. it has more then enough power and has no trouble getting on plane. my dock neighbor has the 2556 with 7.4 and bravo 2 we cruise at the same speeds and burn about the same amount of gas. we cruise at speeds of 25-27mph and max speed is 38mph when im low on fuel and water with light gear on board. I think the 5.0 mpi will be nice for relabilty, and smooth running, i know i like mine, but the 5.0 is not going to have enough torque. why not purchase a new long block and switch over the mpi, alt, starter, he and so on to the new long block either 359/383?

**2850Bounty** · 06-02-2012, 10:38 PM

Mick, I posted to your thread is because I have done these engine and drive changes. Several have been on 2556's whereby the Duo Prop was added.

I've also done these on the 28's with single engines.

reeltrouble has just offered his experience with his 2560.

Note his comment about running at close to the same speeds as his dock mate....., yet his engine is a 5.7L w/ DP, and the other is a 7.4L w/ BII.

I believe that the 2560 is very similar to the 2556.

As I suggested earlier, two great options would be:

the 377/383 while staying with your BII drive.

the 377/383 with the Duo Prop.

.

**Guest** · 06-02-2012, 11:22 PM

2560 is the same boat wiyh minor changes through the years. the first 2 years of the boat it was model stamped 2560 then went to the 2556. and my boat with the small block sits at least a couple of inches higher out of the water then the 2556 with big block engine.

**Guest** · 06-03-2012, 05:33 AM

i really appreciate your experience 2850Bounty is it an option to change short block

for a more hp block and still run same mpi gear .

reason i bought this is i blew up upper gear box in my sterdrive and all mechanics in

australia wanted $4000 dollars to repair i bought whole engine sterndrive gimble gauge ,

every i could possibly need to make my boat run for $6000 i couldnt knock it back so

here we are have i made a big mistake.

cheers mick

**2850Bounty** · 06-03-2012, 06:06 AM

mick302351 wrote:
.......... is it an option to change short block for a more hp block and still run same mpi gear?

Mick, a short block is minus cylinder heads.

You would not want to use the 5.0L cylinder heads on a 5.7L or 6.2L.

As for the MPI working on a 5.7L or 6.2L, ask your Merc dealer or Roger at MichiganMotors.

I'm not familiar with Merc's drive ratios, but I'm thinking that the 2.2:1 ratio will be incorrect for a 5.7L or 6.2L.

Over-all drive ratios are predicated by the engine!

.

**Guest** · 06-03-2012, 06:42 AM

reeltrouble wrote:
i have the 2560 with a mpi 350 and volvo duo prop. it has more then enough power and has no trouble getting on plane. my dock neighbor has the 2556 with 7.4 and bravo 2 we cruise at the same speeds and burn about the same amount of gas. we cruise at speeds of 25-27mph and max speed is 38mph when im low on fuel and water with light gear on board. I think the 5.0 mpi will be nice for relabilty, and smooth running, i know i like mine, but the 5.0 is not going to have enough torque. why not purchase a new long block and switch over the mpi, alt, starter, he and so on to the new long block either 359/383?

i think i meant to suggest buying a new long motor. is that an option

**itsabowtime2** · 06-03-2012, 07:03 AM

I think you may be OK.

Here is why.

Bayliner put 260hp 5.7 Volvo's with single prop drives into the 2550's, 2850's, 2750's of the 80's. These boats would not break any speed records, but that was not the intent.

Do you loose valuable torque, yes. And torque is very important on a boat. But what do you gain, much better dock side manners, ease of starting, better lift while on plane and substantial weight loss.

Fast forward to 2005 to X. Many pocket cruisers have the same engine / drive set up as what you have purchased.

The Sea Ray 240's

Regal 2465's

Rinker 250's

Bayliner 265's

Point is, I think you will be OK.

Good luck.

**2850Bounty** · 06-03-2012, 07:08 AM

mick302351 wrote:
i think i meant to suggest buying a new long motor. is that an option

Long block as in a 5.7L SBC......., or as in another 7.4L BBC?

https://"http://www.baylinerownerscl...ost # 48 here.

Because of your hull weight and size, this info could be useful if you go with a SBC, rather than a BBC.

.

**Guest** · 06-03-2012, 07:50 AM

i was refering to sbc in conjunction with the mpi gear i already have

I cannot understand what relevance timing from "side note of #48" has with my hull size and weight

regards mick

**2850Bounty** · 06-03-2012, 08:19 AM

mick302351 wrote:
I cannot understand what relevance timing from "side note of #48" has with my hull size and weight

regards mick

Understood..... and that's OK.

In part, this is why you thought a 5.0L would power your boat adequately.

No offense, you may have been lead to believe that it would work well!

What that equates to, is that ultimately (for me anyway) this boat needs a good quench built 383 engine, or at minimum, a quench built 5.7L engine and a Duo Prop drive.

Again.... this would be for me!

What Mick does is entirely up to Mick.

I'm just making a few suggestions after having seen, worked on, owned, talked about, read about, and re-powered under-powered boats.

Too much power is never complained about, but too little power is complained about.

In more cases than not, getting this boat up and out of the water (planing attitude) will offer you a more efficient operating range.

.

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