What engine? Fuel, reliablity, price?

[crazymac-680]

I currently own a Mercury blueband 850 85hp thunderbolt ignition. I've had 4 good years out of her without any major issues but with her being 40 plus years old, I am on the lookout for a replacement.
My Merc is very heavy on fuel flat out. She will use 50ltrs in 30miles at 40mph. However if I slow to 20-22mph the same journey uses 26 litres.

I feel that my merc is gonna carry on forever but she just seems very heavy on fuel and that is holding back the length of trips we can go on. So I would like the replacement to have a marked improvement in fuel economy.

Would a Yamaha 90hp 1990(seen for ?1300) give me this improvement? Or would I have to fork out for a 2003 90hp Yam(?3000). I like the simplicity of the older Yam. I could do all the work myself but that may not be the case with the newer Yams?

What are your opinions and is there any other engines I should be looking at? I like on an Island in Scotland and we dont have dealers to take the engines to.

Thanks for any advice
Dan

 

[kenmyfam]

Re: What engine? Fuel, reliablity, price?

Which island are you on ???
Generally an outboard will use 10% of it's HP in gallons per hour at WOT. It doesn't matter what make it is.
100 HP = 10 GPH at WOT
Therefore you will be using that amount no matter what the motor. As you have already said, slowing down and reducing the RPM significantly reduces fuel consumption and that is the way I do it with our outfit.

 

[crazymac-680]

Re: What engine? Fuel, reliablity, price?

Thanks Kenmyfan
I'm guessing you are managing to get the 10gph out of your engine? I'd be delighted with that. By my calculations I am burning 15gph flat out. I find it good news that engines in the 1986 era are achiving 10gph. Does that rule of thumb apply for newer injection 2 stroke models?
Thanks again
Dan

 

[crazymac-680]

Re: What engine? Fuel, reliablity, price?

Thanks Kenmyfan
I'm guessing you are managing to get the 10gph out of your engine? I'd be delighted with that. By my calculations I am burning 15gph flat out. I find it good news that engines in the 1986 era are achiving 10gph. Does that rule of thumb apply for newer injection 2 stroke models?
Thanks again
Dan

 

[crazymac-680]

Re: What engine? Fuel, reliablity, price?

Sorry forgot to say. I'm on the Isle of Lewis

 

[Rancherlee]

Re: What engine? Fuel, reliablity, price?

I find the newer DFI 2 strokes and EFI 4 strokes to be below the 10g/100hp rule. I know my Johnson/Suzuki 70hp 4 stroke "sips" fuel at ~5.5gph running WOT @ 6100rpm (actually tested it once on a 25+mile long lake and it took 5.5 gallons to top off that can after 1 hour of use). Mt buddies E-tec 60 is similar, his used 5.5 gallons also an a similar run as he likes to compare his New Rude to my 11 year old Johnsuki. The engine I replace on mine was a 88' Johnson 2 stroke 70hp triple and that was over the rule as it would drink a whole 7 gallon can in just under an hour. My 88' 2 stroke Johnson 88hp SPL was over 10 gallons an hour and only 3mph faster than my 70hp johnsuki.

 

[Silvertip]

Re: What engine? Fuel, reliablity, price?

I suggest you visit all of the engine manufacturers web site and check their "Performance Test" pages. If you are keen on Yamaha, they have one of the most comprehensive listings I've seen. Pick a boat, pick a technology (2/4 stroke), pick an engine and they provide as much info as one would normally require to make an intelligent analysis. While they don't obviously list every boat/engine combination, it is an impressive collection of data. Other manufacturers have similar data but nearly as complete.

 

[Chinewalker]

Re: What engine? Fuel, reliablity, price?

To answer the initial question, yes, the 1990 Yamaha will give you noticeably better fuel economy over the old Merc. The Yamaha is a loop-charged engine, which is a more efficient design.

 

[robert graham]

Re: What engine? Fuel, reliablity, price?

I believe Silvertip is referring to: Yamaha Performance Bulletins, where you put your boat and motor combination in and it gives you the MPH, MPG, GPH for your particular rig. Regarding the older Yamaha 90HP 2 strokes premix outboards, that's what I've run for years with no problems at all, but for any fuel economy you'll still need to stay in your cruise range, maybe 3500 RPM's. Open it up and you'll suck down about 9 gallons per hour. The 4 strokes do better on fuel economy, but with the price of weight, complexity, service, etc. If I lived on an island and wanted bullet-proof reliability, then I'd buy a good premix 2 stroke of about 70 to 90 HP, then I'd get a water/fuel seperator from Walmart for $27, install on transom. Maybe you should just keep your old Mercury.

 

[crazymac-680]

Re: What engine? Fuel, reliablity, price?

Thanks everyone for your opinions. I am 100% sticking with 2 stroke and am delighted to hear the the late 80s and early 90s engines are much more fuel efficient than my Merc.
Are the newer fuel injection 2 strokes more difficult to work on or less reliable than the 90s carb versions?
I must say I'm not in a rush to get rid of the old lady Merc but I'd just really like to go on longer trips.
Thanks again.
Just for your information. I have a Avon searider 5.4 that does 40mph with my Merc on a 13/21p prop 2 people up.
Dan