DeanFish Posted November 18, 2012 Share Posted November 18, 2012 Hi guys, I have a Evinrude 70hp 2 stroke (1997) outboard pushing my 4.3m markham dominator. The fuel consumption appears to b excessive. The tank holds 45 Litres and I can only get about 25km out of a tank. Is this normal? Link to comment Share on other sites More sharing options...
Geoff Posted November 18, 2012 Share Posted November 18, 2012 It depends a lot on the RPM , eg , you will consume more running at 5000 rpm than running at 3500 - 4000. Not sure if this is a reasonable comparison but my 2003 70hp 2s Yammie averages one liter per mile (1.6km) but I rarely go over 4000 rpm. This is an average over a days outing so includes both time on the plane & moving at lower rev's from on spot to another Your currently running at 2.9 lt / mile (1.6km) which , at nearly 3 time the consumption , seems excessive Geoff Link to comment Share on other sites More sharing options...
dunc333 Posted November 18, 2012 Share Posted November 18, 2012 seems very high to me ,if i was you a service and compresion test would be a start ,let us know your results cheers dunc333 Link to comment Share on other sites More sharing options...
a boat Posted November 19, 2012 Share Posted November 19, 2012 Hi, any carby engine of that vintage will be about that fuel burn pushing such a boat thru the water, which is ALOT harder than say a 15 foot tinny. As for compression, it will not affect fuel economy, but if it is not even performance will not be good and I bet you are not set-up or propped right. You want to see around 5600RPM at WOT with normal load and be able to see the AV plate. If you are overpropped and too low your engine is lugging and like driving around with the park brake on. The simple facts are nothing will improve the fuel consumption because any carby outboard draws the amount of fuel the engine needs thru fixed jets BUT that boat is hard to push thru the water and as I said making sure the basics are right like correct prop and engine height are the first steps to get the best fuel burn. What plugs do you have because I also bet they are wrong. Cheers, Huey. Link to comment Share on other sites More sharing options...
Guest Aussie007 Posted November 19, 2012 Share Posted November 19, 2012 wow $60 to fill up and only get 25km's i fill up $30 and get around 80km's i have a smaller hp engine and different boat your engine sure is a guzzler Link to comment Share on other sites More sharing options...
a boat Posted November 20, 2012 Share Posted November 20, 2012 wow $60 to fill up and only get 25km's i fill up $30 and get around 80km's i have a smaller hp engine and different boat your engine sure is a guzzler That comment is a total waste of time, a small tinny is going to always be better on fuel than a multi-hull just like a 14 foot cataraman is going to be alot better than a 40 foot multi-hull. As I said any outboard, especially an old tech engine, on a multi-hull boat is going to use alot of fuel becuase multi-hull boats are very hard boats to push thru the water and have alot of wetted area that is friction-simple as that. You take that exact same engine off that hull and rig and prop it correctly on a 15 foot tinny and the fuel usage would be half. Link to comment Share on other sites More sharing options...
Guest Aussie007 Posted November 20, 2012 Share Posted November 20, 2012 That comment is a total waste of time, a small tinny is going to always be better on fuel than a multi-hull just like a 14 foot cataraman is going to be alot better than a 40 foot multi-hull. As I said any outboard, especially an old tech engine, on a multi-hull boat is going to use alot of fuel becuase multi-hull boats are very hard boats to push thru the water and have alot of wetted area that is friction-simple as that. You take that exact same engine off that hull and rig and prop it correctly on a 15 foot tinny and the fuel usage would be half. not everyone is going to post comments u like huey? its a discussion forum mate Link to comment Share on other sites More sharing options...
a boat Posted November 20, 2012 Share Posted November 20, 2012 not everyone is going to post comments u like huey? its a discussion forum mate Not sure what you mean I did not say I dislike your comment-I said it was a waste of time and is not at all a fair comparsion and yes a Micra uses less fuel than a Patrol, or a Corolla uses less for than a Landcruiser-I could go on all day doing these useless comparsions. Comparing a mono hull tinny to a multi-hull is a total waste of time and to say that engine is a guzzler is totally wrong and it is no better or worse than any engine of its age, it HAS ALL got to with the hull. Yes I understand the principle of a forum mate. Link to comment Share on other sites More sharing options...
Guest Posted November 20, 2012 Share Posted November 20, 2012 Easy now gentlemen please stick to the point at hand from the original poster. Admin Link to comment Share on other sites More sharing options...
Guest Aussie007 Posted November 20, 2012 Share Posted November 20, 2012 Not sure what you mean I did not say I dislike your comment-I said it was a waste of time and is not at all a fair comparsion and yes a Micra uses less fuel than a Patrol, or a Corolla uses less for than a Landcruiser-I could go on all day doing these useless comparsions. Comparing a mono hull tinny to a multi-hull is a total waste of time and to say that engine is a guzzler is totally wrong and it is no better or worse than any engine of its age, it HAS ALL got to with the hull. Yes I understand the principle of a forum mate. all good huey do u know how many litres of fuel the 70hp uses max per hour? i just tried looking it up in the workshop manual i have but it doesnt mention it Link to comment Share on other sites More sharing options...
a boat Posted November 20, 2012 Share Posted November 20, 2012 (edited) all good huey do u know how many litres of fuel the 70hp uses max per hour? i just tried looking it up in the workshop manual i have but it doesnt mention it Hi Gazza, no problems my end either and you will never seen any such info from any outboard manufacturer because it will varying depending on the hull and that is why I replied to your first post. That 70HP, or any 70HP-clean or dirty, will use alot less fuel on a light weight easy to push thru the water hull then compared to a deep vee hull or even worse cat style boat. As a very rough guide a carby engine on such a boat would use close to 60L/hr at WOT but at cruise speed or idle that of course will be alot less. The way a person drives their outboard, again I do not care what brand, will vary fuel usage as will making sure the engine is not too low or overpropped and as I said in my first reply to this gentleman make sure he is seeing the correct WOT RPM and the AV plate is eaisly visible when trimmed correctly-otherwise his fuel economy is going to suffer no matter what brand of outboard any brand of boat has. It is one of the many challenges for the outboard companies, unlike a car company that knows a certain engine is going to go in a certain chassis, an outboard can go on thousands of different hulls that all perform differently so comparing one boat to another boat is a waste of time and making sure any rig is set-up to its optimium is the best way to get the most out of every litre of fuel. Cheers, Huey. PS- lets see what this gentleman gets back to us with in terms of WOT RPM, prop, engine height and what plugs he is running and then we maybe able to improve his performance, not only fuel but speed too. Edited November 20, 2012 by Huey @ Huett Marine Link to comment Share on other sites More sharing options...
Frantic Posted November 20, 2012 Share Posted November 20, 2012 id also like to know is that distance via gps so its accurate and is the boat driven up the backwaters where its glass flat or where its hindered by swell. Link to comment Share on other sites More sharing options...
DeanFish Posted November 20, 2012 Author Share Posted November 20, 2012 Hi gents, I really appreciate the feedback. im not real mechanical so can i confirm WOT (assuming that wide open throttle?) = 5800 Engine height = how do I measure this Prop = evinrude 13.25 x 17R Plugs = Champion (that's all I can tell you) I also have a SE sport 300 hydrofoil (not sure if that's the correct terminology) apparently assists the boat to get on the plain quicker? I appreciate any further advice. Link to comment Share on other sites More sharing options...
dunc333 Posted November 21, 2012 Share Posted November 21, 2012 i should have known better when i saw markam .its a twin hull as huey said theres lots more boat to push than a mono hull and if your setup is right,your wot sounds ok ,so if you can take a pic from the back of boat and of the motor height,huey might be able to see if thats all good but as now i know its a twin hull your fuel consumption could be on the money cheers dunc333. Link to comment Share on other sites More sharing options...
a boat Posted November 21, 2012 Share Posted November 21, 2012 Hi gents, I really appreciate the feedback. im not real mechanical so can i confirm WOT (assuming that wide open throttle?) = 5800 Engine height = how do I measure this Prop = evinrude 13.25 x 17R Plugs = Champion (that's all I can tell you) I also have a SE sport 300 hydrofoil (not sure if that's the correct terminology) apparently assists the boat to get on the plain quicker? I appreciate any further advice. Hi, if those RPM are accurate then you are turning high RPM and as a result the engine is revving harder than it needs so fuel burn will go up. Ideal WOT RPM wants to be about 5500-5600RPM for that I-3 and if you switch out to a SST prop performance and fuel economy will improve. You want to be able to see the AV plate clearly when trimmed correctly and any foil will cause the stern to lift and therefore burying the bow making it even harder to push thru the water. As for the plugs see what is stamped on the plug to see if they are correct but at least it is the right brand. Cheers, Huey. Link to comment Share on other sites More sharing options...
dunc333 Posted November 22, 2012 Share Posted November 22, 2012 (edited) can i ask huey what is the biggest hp you can have on this markam 3.5 and if its say 70hp ,as most i have seen have twin engines if the capacity plate says 70hp for example can you have twin 70hp on a twin hull or would you have to have 2- 35hp engines to be legal.? Edited November 22, 2012 by dunc333 Link to comment Share on other sites More sharing options...
DeanFish Posted November 22, 2012 Author Share Posted November 22, 2012 Really appreciate the FB. I'm out this weekend so I will keep any eye on a few things. I will look to cruise at lower Revs to see if this makes a significant difference. Link to comment Share on other sites More sharing options...
DeanFish Posted November 22, 2012 Author Share Posted November 22, 2012 Dunc333. I know the Markham 4.3 is rated to 1x70hp or 2x 40hp. Link to comment Share on other sites More sharing options...
dunc333 Posted November 23, 2012 Share Posted November 23, 2012 ok thanks dean that clears that up for me,if you ever upgrade engines try 2 40hp 4strokes as i reckon you would use a shit load less fuel than your using now with 1 engine. Link to comment Share on other sites More sharing options...
a boat Posted November 23, 2012 Share Posted November 23, 2012 (edited) ok thanks dean that clears that up for me,if you ever upgrade engines try 2 40hp 4strokes as i reckon you would use a shit load less fuel than your using now with 1 engine. Or two 40HP E-TEC and use even less fuel and be able to plane that boat on one engine which is the whole point of twin rigs. Or repower with a single E-TEC and again use half the fuel and cost ALOT less to buy and maitain than twin 40HP 4-Strokes and would go better too. Cheers, Huey. Edited November 23, 2012 by Huey @ Huett Marine Link to comment Share on other sites More sharing options...
Geoff Posted November 25, 2012 Share Posted November 25, 2012 Dean Fish. I've seen some Markham's which only have one engine with that engine mounted on the Port side behind the sponson. Is your motor mounted in the center or on the side of the transom. Also , for interest , the fuel consumption mentioned in my post , 19/11/12 is for a 4.9mt twin hull Aluminium boat. Before you throw too much cash at the problem I would be taking the boat to Huey to have the height & prop checked along with a full service. It maybe just a carby adjustment , air filter , fuel pump check to ensure fuel is not leaking directly into the cylinder , timing & a new set of plugs. Geoff Link to comment Share on other sites More sharing options...
DeanFish Posted November 27, 2012 Author Share Posted November 27, 2012 Thanks Geoff, I recently had it serviced but i had already planned to take it to Huey given the trouble he has gone to with the previous advice.I will take your advice onboard and will take it him for sure. Regards. Link to comment Share on other sites More sharing options...
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