Which fuel to use?

[SkaterRace]

I have a Mercury 2019 225HP XL on a boat I just bought and have yet to pick up. I checked the Mercury website and PDF, it shows to use 87 fuel but everything I have ever heard is marine engines work best with 91/premium and that is all the marinas around me sell too far as I know. I am wondering if it is worth shelling out for the premium fuel or if I can stick to 87/regular?

 

[alldodge]

It's the age old thing of it has to run better on high octane fuel, because its high

High only means it burns slower, so if timing is set for low then use low because it burns faster

Always use what manufacture requires for best performance

 

[RMClark]

It's the age old thing of it has to run better on high octane fuel, because its high

High only means it burns slower, so if timing is set for low then use low because it burns faster

Always use what manufacture requires for best performance

Yup.

Higher octane gasoline has the same amount of energy in each gallon as the lower octane counterpart. Higher compression engines may need the slower burning characteristics of the higher octane fuel.

Follow the manufacturer's guidance.

 

[Scott Danforth]

Higher octane means less BTU/s per gallon (as the octane level goes up, the actual energy of the fuel goes down)

87 octane gasoline (e0, not e10 blend) has 125,000 BTU/gallon
106 octane gasoline has 120,000 BTU/gallon

e10 87 octane has 120,000 BTU/gallon

ethanol has 84,600 BTU/gallon (however an octane rating of about 140)

the higher the octane rating, the harder it is to ignite. so performance cars with high compression need higher octane to prevent pre-igntion

your boat is designed to run on 87 octane rated with the (R+M)/2 method

anything higher than what is required is just more expensive and doesnt help a stock motor. it wont improve performance

 

[tpenfield]

Be careful what you hear and the Mercury published literature/info probably is giving a good recommendation.

 

[SkaterRace]

Thanks all! I will be running 87 in it this summer then so hopefully with prices being cheaper I can have an excuse to get out more

 

[Scott Danforth]

Thanks all! I will be running 87 in it this summer then so hopefully with prices being cheaper I can have an excuse to get out more

Fuel is still the cheapest part of boat ownership.

every time I head out its $60-100 in fuel

 

[SkaterRace]

Fuel is still the cheapest part of boat ownership.

every time I head out its $60-100 in fuel

Oh yeah, it's the cheapest by far lol My payment is the most expensive part for me. Just with cheaper fuel, it means that the money I set aside for the boat for the year means I have more room for fuel than I did before. I budget tightly so I will set a budget for the boat's monthly cost (averaged out over the year for things like winterization, repairs, etc), and out of that so much is taken up by payment, insurance, etc leaving usually about 1/4 to 1/3 for the fuel. So I was planning on $1.80/L for fuel and now $1.35/L for fuel is over 20% more fuel. A weird way of doing it I know but it works for me since I learned the hard way, if I don't set a budget for the boat I will spend literally everything I can on it while still paying my normal bills.

 

[dingbat]

I budget tightly so I will set a budget for the boat's monthly cost (averaged out over the year for things like winterization, repairs, etc), and out of that so much is taken up by payment, insurance, etc leaving usually about 1/4 to 1/3 for the fuel. So I was planning on $1.80/L for fuel and now $1.35/L for fuel is over 20% more fuel.

Budgeting and boating are never a good fit...lol

If nothing else it's the incidentals that kill you. The last three boat's I bought necessitated vehicle upgrades shortly there after.

What rate of fuel burn have you planned for?
Just cruising (27 kts.), I'm pretty consistent burning 1kM/L of fuel over a season
Pretty easy to burn up 400-500/L on a long weekend

 

[SkaterRace]

Budgeting and boating are never a good fit...lol

If nothing else it's the incidentals that kill you. The last three boat's I bought necessitated vehicle upgrades shortly there after.

What rate of fuel burn have you planned for?
Just cruising (27 kts.), I'm pretty consistent burning 1kM/L of fuel over a season
Pretty easy to burn up 400-500/L on a long weekend

Yeah budgeting and boating doesn't fit well but I have to lol I gave up on retirement savings for 3 years over my Glastron I agreed with myself on that I would set a budget for boats and not break it or I would not get a boat because I don't want to end up screwed and working till I die.

The random stuff I try to budget for too, normally I "cheat" by going with the max I ever think is possible as my budget then just using that extra the next year on upgrades or more fuel.

I am planning on a burn rate of 40L/h which I think should get me 30 MPH on the St Lawerence. I have a Blackfin 212CC with the 225HP XL Merc on the back. Not the fastest or best on fuel but a good enough mix for where I am. I am basing this on the Mercury performance data for RPM and comparing that with the data on the Blackfin 222CC with the same engine which the sales guy said is the same boat just a different nameplate and some interior upgrades. Funny enough he talked me out of ordering one as my next boat in 2-3 years as the boats are too similar.

I am planning on 14 weeks of boating season - May 24 to Labour Day weekend - then 7-10 hours of engine runtime weekly provided I can bring enough people with me to allow it.

So my math says an average of 40L/h x 10 hours x 14 weeks is 5600L of fuel on the high end. I do have some trips planned that will burn a lot of fuel on their own too so my guess is probably 6500L of fuel for the summer.

 

[airshot]

Once again big daddy ( US Gov't) tells the manufacturers that there engines must be designed to run on 87 octane fuel, same with autos. Many mfgrs will state there vehicles are designed to run on 87 octane to meet gov't requirements....but actual performance will be better using higher octane fuels. One company is Fiat, they advertise X hp and 40 plus mpg with 92 octane...but when using the gov't recomended 87 octane fuel thevhp dropsvand fuel economy drops to 35 or something mpg. Volkswagon does the same thing !!
I recently bought a 1992 Merc classic 40hp OB , after much research the findings are...it will perform on 87, but on some Mercury forums old posts from way back the mfgr recomends a min of 91 octane for best performance. According to a Mercury letter sent to mechanics, posted by a retired Merc mechanic the V6 performance engines required 93 octane, but the original owners manual claim they are designed to run on 87, however, performance and improved durability can be gained by using 93 octane !! Not sure how much has changed since then, but I would have a serious conversation with a factory Merc service tech and see if any behind closed door recomendations are needed....

 

[dingbat]

I am planning on a burn rate of 40L/h which I think should get me 30 MPH on the St Lawerence. I have a Blackfin 212CC with the 225HP XL Merc on the back. So my math says an average of 40L/h x 10 hours x 14 weeks is 5600L of fuel on the high end. I do have some trips planned that will burn a lot of fuel on their own too so my guess is probably 6500L of fuel for the summer.

I think you’re over estimating fuel usage by a good bit

I’m running a bigger, heavier boat (Grady White 226) with less efficient 2 stroke engine technology.
Gets roughly 1 kM/L at 27 kts in good conditions. Fuel usage can double when things get sloppy

Working backwards from your estimated 6500 liters of fuel, your expecting to use 464 kM of fuel per week.

This of course assumes you go and do everything at 30 mph, ignoring the fact that half the hours put on a large HP motor are typically spent at or below wake speeds where fuel consumption fuel is negotiable.

Just my opinion, but planning to use 464 kM of fuel a week is rather ambitious/optomistic for a 21’ boat on a large, open body of water.

 

[SkaterRace]

I think you’re over estimating fuel usage by a good bit

I’m running a bigger, heavier boat (Grady White 226) with less efficient 2 stroke engine technology.
Gets roughly 1 kM/L at 27 kts in good conditions. Fuel usage can double when things get sloppy

Working backwards from your estimated 6500 liters of fuel, your expecting to use 464 kM of fuel per week.

This of course assumes you go and do everything at 30 mph, ignoring the fact that half the hours put on a large HP motor are typically spent at or below wake speeds where fuel consumption fuel is negotiable.

Just my opinion, but planning to use 464 kM of fuel a week is rather ambitious/optomistic for a 21’ boat on a large, open body of water.

Yes, I do plan on spending, not near even half at 30MPH but until I have a summer under my belt and know my usage and such I am planning on the worst case. The 6500L is my worst case and my realistic guess is closer to 3500L of fuel though honestly that might even be high depending on what I end up doing. If I end up going for day rides and go slow then it's high but if I make often trips to see friends and family at the city I used to live in then I will burn around that. I just don't want to only think I am putting in 3500L of fuel and then have it come where I don't go out because of needing more fuel than expected. I plan for the worst case possible and then add a margin of error until I have data to back it up.

The Blackfin site says that with a 225HP at 27.5MPH, I will be 8 gallons per hour, I assume this is calm water and no current. So I am thinking 10 gallons per hour is reasonable for slightly faster and going in non-calm water. That was how I figured 40L/h in a "worst case" since I doubt I would ever go much faster than that for long.

So yes probably way overestimated the fuel for this year and I'm good with that until I have some real data to back up some planning around it. Within the first month, I will have a way better idea of fuel usage per hour and also the types of trips I enjoy most.

 

[harmanoff]

Ive always used and been told do not use fuel with ethanol in it...

 

[airshot]

Been using ethenol fuels since they came out. Even my older gas powered toys. Did a thorough fuel system cleaning and replaced all fuel lines with alcohol approved fuel lines. Not one issue, most issues are due to lack of maintenence, your engine must be set up to use ethanol, if not you will have issues. For long term storage a fuel stabilizer must be used!!! I see no issues using it.

 

[Texasmark]

I have a Mercury 2019 225HP XL on a boat I just bought and have yet to pick up. I checked the Mercury website and PDF, it shows to use 87 fuel but everything I have ever heard is marine engines work best with 91/premium and that is all the marinas around me sell too far as I know. I am wondering if it is worth shelling out for the premium fuel or if I can stick to 87/regular?

Not having read any of the replies, the service manual doesn't say to use 87 it says that 87 is the minimum. If you use the minimum of things, expect minimum results. I switched to premium quite awhile ago and I get much better overall performance. My money, engine, and decision.

 

[jimmbo]

Unless an engine has Knock Sensors, it is tuned to run on 87, and anything higher is a Waste of Money, but I guess it give some guys Woodies when they put the Higher Octane stuff in

 

[harmanoff]

On Mercury's Website it says at min 91 octane fuel...for 2 stroke, 4 stroke, Verado, and Optimax engines

 

[airshot]

My 1992 Merc 40 hp manual says it will operate on 87 but for best performance use 91 octane. I just use mid grade and all is well. Going from 87 up'to 93 octane is a waste of money if your motor is designed to run on 87 as premium fuel burns slower. Some engines will loose performance by going with to high of an octane fuel. However....bottom line is...your money !!

 

[Scott Danforth]

Make sure you guys look at the octane rating system called out in the requirements. RON vs MON vs R+M/2