Help With Engine sizes: 7.4L vs. 350 MAG MPI

[Electriceddie]

Hi Guys,

I am new to boating an I am not familiar with these engines. Now as stupid as this may sound, my first question not knowing the liter sizes to well, these are two different size motors correct?
* How much more powerful is the 7.4L motor?

* If they were both in a 285 Bayliner will the thew 7.4L push it a lot more efficiently?

* I heard that the 350 MAG MPI was marginal and with a loaded boat may even have some difficulty planning off, is that true as well?

* Would the 7.4L be a much better choice?

* Also what speeds are we talking for top end and for cruising around?


Thanks in advance for the help and answers.

Ed

 

[danond]

Re: Help With Engine sizes: 7.4L vs, 350 MAG MPI

Re: Help With Engine sizes: 7.4L vs, 350 MAG MPI

Speed is tough to tell.

7.4 is a 454 V8. 5.7 is the 350. If you ever need quick math just take the liters times 60. It puts you within a few cubic inches.

Go with the 7.4. The 350 will be just enough to push a 28 footer around. The 7.4 won't strain.

 

[Fun Times]

Re: Help With Engine sizes: 7.4L vs. 350 MAG MPI

X 2 a big boat needs more cubic inches for the torq to get it and to keep it movin longer with out hurting the engine, and to help you from getting board from going so slow

 

[Zackman]

Re: Help With Engine sizes: 7.4L vs. 350 MAG MPI

The big block, 7.4L will have more low end torque and get that big ole boat on plane faster I would think.

You do not give the year of the engine(s), but the 7.4L came in two flavors the regular rated around 320 hp and the HO rated around 380 hp. The 350 mag is rated at 300 hp. I believe the rpm for the rated hp is slightly higher for the 350 than the 7.4L, hence the closeness in hp rating even though the 7.4L (lower rated one) will have more torque.​

 

[45Auto]

Re: Help With Engine sizes: 7.4L vs. 350 MAG MPI

I test drove a 2006 Sea Ray 260 Sundancer with a 5.7L. It was very unimpressive. Took forever to come on plane, and the motor was running at 4100 RPM to cruise at about 25 MPH. This was running empty with 1/8 tank of gas and 3 people on board. Can't imagine how bad it would have been if it was loaded down. On something as big as that Bayliner I would want at least a 7.4L. Twin 4.3's would be even better.

Get someone familiar with boats to take it out for a test drive. Drive a few different boats before you make up your mind if you are not an experienced boater.

 

[Electriceddie]

Re: Help With Engine sizes: 7.4L vs. 350 MAG MPI

Hi Guys,

First Off:

Thanks for the quick responses!

The boat and engine are (assuming the engine is original) is an 2000 Bayliner 2855 Sunbridge. The manifolds and the risers were just replaced last year. It has the counter rotating duo props as well.

Thanks again.......

ElectricEddie