Help Buying an Older Boat

[HGM]

Looking to purchase a older Sea Ray. After looking at many boats this summer my family has fell in love with the Sea Ray Sundancer. I am currently looking at a 1991 350 Sundancer with 454's. The boat appears to be in good condition but I will not be able to get any history. I will get a survey before I buy. I currently have a 23' alpha 1, 260. Most of the Sea rays in this area (Chesapeake Bay) are inboards. What difference can I expect with the tunnels? Will this boat 'Plane'? Does anyone have any idea about Fuel usage? Thanks

[Ex-Calif]

Hi HGM and welcome to CF!

I certainly don't have any experience with this type of boat but expect someone will come along soon who does.

[GordMay]

Greetings and welcome aboard the CF, HGM.

By “tunnels”, do you mean their Axius or Zeus pod drive?
➥ Axius Zeus Video

[dacust]

Originally Posted by HGM

Looking to purchase a older Sea Ray. After looking at many boats this summer my family has fell in love with the Sea Ray Sundancer. I am currently looking at a 1991 350 Sundancer with 454's. The boat appears to be in good condition but I will not be able to get any history. I will get a survey before I buy. I currently have a 23' alpha 1, 260. Most of the Sea rays in this area (Chesapeake Bay) are inboards. What difference can I expect with the tunnels? Will this boat 'Plane'? Does anyone have any idea about Fuel usage? Thanks

The tunnels will have no effect you will notice except that it reduces the draft, so less likely to damage your props.

That boat will definitely plane. Easily.

There are others in here better qualified to talk fuel consumption, but I'll guess about 1mpg when running under, say 8mph. 2 gallons per mile running up on plane, maybe more at WOT.

I had a much heavier 36' wood boat (22,000lbs) with gas 360s. It burned 1.5 gallons per mile at 10kts. Might have gotten 1 mpg at 6kts.

My current boat is 36' fiberglass (18,000lbs) with diesels. It burns about half the fuel.

Those were well built boats. If memory serves, engine servicing will be a chore. They are tight. Consider installing a remote oil change setup on it.

-dan

[Shrew]

The calculation for fuel (Gasoline) consumption at WOT should be:

HP x 0.425/6.2 = Gallon per hour burn rate (PER ENGINE).

The challenge here is that gasoline expands and contracts with temprature, unlike water which is relatively consistant. so it's really teh specific gravity of the fuel based on the temperature which dictates it's weight. At 68 degrees F, gassoline weighs 6.15lbs per gallon.

The Mercruier 454 had varied HP reports between 300 - 325 HP. I think 300 HP was a more realistic number.

300 (HP) x 0.425 = 127.5lbs of fuel

127.5 (lbs of fuel) \ 6.2 (lbs per gallon) = 20 Gallons per hour (At wide open throttle.

So you would have a 40 gal./hr. burn rate at WOT for both engines combined. Now, calculate the percentage of WOT. Let's say the engine runs at 4000RPM at WOT, then theoretically, at 3,000 RPM (75%) you would decrease fuel consumption by that amoutn relatively (30 Gal./hr.)

Now these are just rough numbers, and they WILL vary. Saying "well, I get 26gal. when the numbes say 30 is a minor varation. It is also based on a properly tuned engine. Many other factors will impact the final numbers, but this is a good start at the least.

How to Calculate Fuel Consumption in Boats | eHow.com

Calculating Fuel Consumption | Boating Magazine