21 Skater fuel exconomy with 300x vs 300xs optimax

**simpson_3** · 05-04-2020, 07:23 PM

I'm looking at some 21 Skater's and was curious about fuel economy. What would be the best mpg with a 2005 300x vs the 2015 or newer 300xs optimax?

**JPEROG** · 05-04-2020, 08:38 PM

If you can find a hull without power, the new 300R would be far and away the best option. If that is not in the cards, you can expect 3 mpg "best from the X" and 5 mpg "best from the XS"

Joe

**simpson_3** · 05-04-2020, 09:07 PM

Originally Posted by JPEROG

If you can find a hull without power, the new 300R would be far and away the best option. If that is not in the cards, you can expect 3 mpg "best from the X" and 5 mpg "best from the XS"

Joe

I've thought about a 300r. Someone told me they break prop shafts. Also wasn't sure how good they are since they haven't been around that long. What would a 300r get for mpg?

**JPEROG** · 05-04-2020, 09:22 PM

It is correct that they can break prop shafts under heavy cavitation "which you will experience with a 21", the cure for this is the 450R one piece shaft. These motor offer so much over the others that its a non-comparison. Fuel mileage will be just shy of the optimax but you will be very happy when its set up correctly.

Joe

**WILDMAN** · 05-04-2020, 11:57 PM

I believe all the 300R's now have the one piece propshaft. Of course they also raised the price $900!

**JPEROG** · 05-05-2020, 02:58 AM

Originally Posted by WILDMAN

I believe all the 300R's now have the one piece propshaft. Of course they also raised the price $900!

They don't.

Joe

**DangerNewb** · 05-05-2020, 05:49 AM

I had a 300 promax for a little while. Milder version of 300x. I dont think I ever saw close to 3mpg on a Seebold Ski Eagle modvp hull. I sold the engine as it was impossible to carry enough fuel to run anywhere. Had a 27 gallon tank. No way I'd own another one.

**JPEROG** · 05-05-2020, 09:01 AM

Originally Posted by DangerNewb

I had a 300 promax for a little while. Milder version of 300x. I dont think I ever saw close to 3mpg on a Seebold Ski Eagle modvp hull. I sold the engine as it was impossible to carry enough fuel to run anywhere. Had a 27 gallon tank. No way I'd own another one.

That and the 250XB where the biggest drinkers in Mercurys outboard history. Both were very dependable motors but used lots of fuel.

Joe

**Brad Zastrow** · 05-05-2020, 09:07 AM

Fuel is least expensive part of boating. For little time we spend on boats gas mileage is the last thing on my mind. On a car you drive every day mileage can be a concern. On a boat I want smiles per gallon. The 300x makes more power then the XS is the factor I would consider.

**WILDMAN** · 05-05-2020, 09:15 AM

Mileage is not the main problem I have found. It's the range. Hard to find 91 octane on the water

**DangerNewb** · 05-05-2020, 09:33 AM

Originally Posted by Brad Zastrow

Fuel is least expensive part of boating. For little time we spend on boats gas mileage is the last thing on my mind. On a car you drive every day mileage can be a concern. On a boat I want smiles per gallon. The 300x makes more power then the XS is the factor I would consider.

Fuel is not the least expensive part of boating if you run small boats like I do. $15k to $20k boat amortized over several yrs vs $300 per month in gas works out to be basically equal. But the $$ wasnt the issue. It was having to carry gas cans in order to do any of the longer river runs. Or even play on the lake for the day. 50 miles was about all I could run on 27 gallons. And if I'm not mistaken, wildman stated he never had a 300x run faster than a 300xs on a 21 liberator but I'm not 100% sure on that. I've considered swapping out my 280 for a 300xs. I know I'll get blasted for for saying it, but I wouldn't mind a little less noise.

**Brad Zastrow** · 05-05-2020, 10:22 AM

Unless modified no way the XS runs with an X motor. XS is 25-30hp less and lower RPM. Do you boat 12 months a year and spend $3600 year on gas? I think a bigger gas tank is lot cheaper route than an engine upgrade. If you really want the gas mileage than the XS is the way to go. The 280's and 300X are both hard on gas. Interesting thing is the direct injection uses nearly as much fuel at WOT as the fuel injected engine. HP takes fuel to make power. Where they really shine is the midrange cruise speeds.

**WILDMAN** · 05-05-2020, 11:36 AM

My statement on the 300x and 300xs running the same is based just on the Checkmates and Liberators. I've never seen a difference in top end. As far as mileage. Running hard all day, on a 21 Liberator, the 300x gets 2 mpg and the XS gets 4. On a twin 25 Liberator running hard, the X gets 1.5 and the XS gets 2.4 mpg. It doesn't matter if you have $100k with you in your boat, if you're out of gas, you are out of gas!

**engineermike** · 05-05-2020, 05:29 PM

Not that it’s completely relevant but my 23’ eliminator peaks at 4.4 mpg with a 400r. With twin 300 vmax motors it got 2.25 at best. I have complete fuel economy vs speed curves of the 400r with half a dozen different props. At times, there was 30% difference from one prop to the next.