Buying twin engine boat, how big of a difference between Twin V8s, Twin V6's, and T-4

[4winnsskipper]

Greetings, im looking into 27' sea ray amberjacks to purchase and im seeing the same model boat with twin 4 cylinders, twin 6's, twin 8's (5.0 and 5.7s). With such a wide range of power im wondering a couple of things. The boat will be used PRIMARILY for trolling (2.0mph) about 1 - 5 miles offshore, about 2 to 4 times a month. SO i'd estimate about 10-20 hours use a month.

a) what is the real world gas usage difference here? I know you can't just say an exact amount as it varies but im wondering conditions being equal, will the twin 5.0 v8s use that much more? Im trying to figure out how much more throttle the 4's will need to go the same speed and plane... just looking for input here...

b) anything i should look for in both? like power steerring on both motors or is just one ok? i notice most have it on just one motor

c) being used 20 hours a month or so will my pocket see much of a difference between running out 2-3 miles offshore , trolling and coming back - montlhly expense wise between twin 6's and twin 8's? Again im taking in account the amount of work motors will need to do since the v8's will see less strain whereas the 4 cylinders may need to be at full song to even get on plane?

any advice is appreciated.

 

[JoLin]

Re: Buying twin engine boat, how big of a difference between Twin V8s, Twin V6's, and

You don't say what year these boats are but if memory serves, those 4-cyls will be the infamous Merc 3.7 liter (model 470). I know somebody will blast me, but it's a terrible design that doesn't put out enough hp (170?) for your needs anyway. Stay away.

You won't see a big difference in consumption between the 6's and 8's, and in some instances (like hauling a heavy load of passengers) the 6's will struggle. The load in my boat is typically just my wife and I and the V-6's work very well, but mine are also injected and put out 210 hp each. If the boats you're looking at are carb'd I'd want V-8's. Either 5.0 or 5.7 will work nicely, with the 5.7's putting out more power with little, if any, fuel consumption penalty over the 5.0's. Again, I think you'll be happy with either V-8, so let the condition of the boat dictate your choice.

Hope that helps. Good luck!

 

[Chris1956]

Re: Buying twin engine boat, how big of a difference between Twin V8s, Twin V6's, and

Probably the V6 motors would be marginal for that boat. I doubt the 4s would work well at all. 5.0L V8 motors would probably work well. Most 30 footers like that boat have the 5.0s. They are a bit underpowered for my taste, but the boat you consider is significantly lighter. On a boat like that you want large enough engines so you can run 'em at about 3200RPM to cruise and be solidly on plane. They will be better on fuel that way.

 

[25thmustang]

Re: Buying twin engine boat, how big of a difference between Twin V8s, Twin V6's, and

I agree, the 4cyl version will likely be 3.7 powered and those motors had bad reputations. With that said I know owners of them who like them. The boat directly behind mine now is powered by twin 470s (the older version 3.7s). Its a 25' Cuddy and it runs very well with these motors. A 27' with a 10' beam boat that should weigh a bit more might perform so so. Another thing I have noticed with twin 3.7 powered boats... They place the motors very close. Number one this hurts if you wanted to repower to larger V6 or V8s, as there isnt the room and the engine bay and transom would need to be redone. Number two as far as slow speed handeling, the closer together the worse.

The V6 version should be the 4.3s and would most likely perform a little better than the 3.7s, as the power between them is actually fairly close. The 4.3s would be the better engine choice.

The V8 version is probably your best bet. The least room in the engine compartment, but you never hear people complaining about too much power.

As for fuel economy, the 4.3s vs the 5.0s or 5.7s probably wont be too large of a gap. It's still a 7000+ lb boat, and will require a bit of fuel to get her on place and running on cruise.

 

[rbh]

Re: Buying twin engine boat, how big of a difference between Twin V8s, Twin V6's, and

If the 270 Amberjacks you are looking at are 1985-1989 +- and are 10 on the beam they are probably the same hull as my sundancer.
We have twin 260's (V8) and are running 14x20 pitch great hole shot, but max out at 40 MPH+-, if we went 15x19 we would top out around 49 MPH+-.
To get on plane takes under 10 seconds and I do not use the trim tabs.
Full out it is a gas guzzler, but if I keep it around 28-3200 RPM thats my best MPH to RPM point.

 

[JoLin]

Re: Buying twin engine boat, how big of a difference between Twin V8s, Twin V6's, and

Just for the heck of it I went to the Searay archives and checked a 1986 27' Amberjack. Huh! With the 4-bangers it's 1400 lbs lighter than my Vista, so figure 1000 lbs difference with V-6's or V-8's. I still like the idea of V-8's for offshore use, but a really nice V-6 equipped boat might be worth a look-see.

Though really heavy passenger loads (6 or more adults) tax my boat a bit, with the wife and I aboard she cruises beautifully at 3200 rpm/22 knots/25 mph. She tops out at juuusssst about 40 mph.

My .02