View Full Version : Tower of power = great fuel economy?!
Dean1
18-03-2012, 08:00 AM
Ive recently bought a 560 Shark cat with a mate and it has 2 x 90hp Mariner inline 6 2 strokes early 80's model. I was never overly keen on these and was ready to rush into a repower mainly for fuel savings for more range. Well did a maiden vouyage to 1770 2 wkends ago and was blown away by the little fuel they use. This is built to survey and is a fair lump heavier than a 5.2kc. It holds 360 ltrs of fuel. With 400 ltrs of fuel on board large esky full of ice, gear etc. We got better than 1 klm per 1 litre for both and roughly 25-30 litres an hour at a nice cruise of around 24 kts. It was pretty rough too. I was getting around the same with a full load in my KC with f 60's.
I know 3 cyl 90 yamaha's dont come close to this my mates have/had them. Is it because they are a 6 cyl motor and they arent working hard?? They had a heap of punch still with a full load and cruise on 24 kts very easy with a load.
If they keep running and behave themselves im putting up with the 2 stroke fumes and oil coz we arent going to save much on fuel going to 4 strokes i cant see the point apart from reliability. we had the timing retarded to suit the fuel nowadays and noticed a power drop, man they were angry with full advance before we did this!
Anyway thought id just share that, not too many people know about these old beasts but would love to hear from those who do know.
Thanks, Deano.
rodneyk
18-03-2012, 09:50 AM
Hi Dean i owned a few brand new ones in 84and 86 bought one of the last ones when thy stopped building them we used to run bribie to tempest anytime we had weather first one was on HH580SLF 40 MPH ringing its neck 2nd one 18ft aussie alloy plate both 115hp used to get 1nm per litre from platey they were great motors in there day think from memory they run jets out with the next size number drill to help them . But then came the 115hp yammys a tad thirstier but great motor . PS keep eye on side plates and bottom seals or just run them till they hand grenade Cheers ROD
Floating Rib
18-03-2012, 10:34 AM
Interesting post Dean, just proves that a repower isnt always the way to go, if you take into account cost of an upgrade and the diff say a new 4 stroke or efi 2 would use fuel wise it may take several years or never to recoup your outlay,
whilst ever they are running fine you are ahead i think, be interested to know what cc capacity they are, as you mentioned a big 6 when not pushed probably can provide good economy.
Dean1
18-03-2012, 11:30 AM
Hi rod, yeah we have already replaced the starboard side gasket on the side plate luckily it was spotted when i had it in at Holt Marine Shane spotted it straight away. also we have replaced 2 Switchbox's which had been obviously blown for a while and makes them run on only 4 cyl's. Ye run them till they pop hopefully get a few yrs outa them if we look after them ( dont flog them) as the power delivery from them is pretty awsome and that fuel economy and having 2 of them been a cat youl always get home youd think so happy days. also gives us good range with the big 2 x 180ltr tanks. It will be only used to fish 1770, Fraser probably 6-8 times a year. It owes us 23k to date with all new electrics including 585 Furuno 1 kw thru hull etc. Cheers.
Hi Dean i owned a few brand new ones in 84and 86 bought one of the last ones when thy stopped building them we used to run bribie to tempest anytime we had weather first one was on HH580SLF 40 MPH ringing its neck 2nd one 18ft aussie alloy plate both 115hp used to get 1nm per litre from platey they were great motors in there day think from memory they run jets out with the next size number drill to help them . But then came the 115hp yammys a tad thirstier but great motor . PS keep eye on side plates and bottom seals or just run them till they hand grenade Cheers ROD
Rod would have meant the exhaust baffle plate Dean, they corrode through & spray water into the cylinders.
If I had those motors I'd change both baffle plates and both lower seals
(they do have a kit if the crank seal surface is bad).
They are 2 things that will kill those motors, especially on a cat where at idle they will sit low in the water.
Only other thing I can think of is make sure you don't lug them, they like to run free. 6000 WOT.
If you notice either one low on WOT RPM then it's time to check out why as leaving it will cost you money.
They make the best noise of any outboard.
Dean1
18-03-2012, 12:38 PM
Thanks for the heads up Fed. These motors are XL's and sit quite high in the water its not bum heavy at all with these donks on. Havent seen the deck get wet once yet even in rough conditions. Funny you say that about reving them hard i was told the opposite as been so old it could finish them off pretty quickly. They cruise at 23, 24kts at 3500rpm easily. Will look into the exhaust baffle'sand lower seals! Wont be spending a fortune on these as soon as one does something half major a repower will be on the cards. Theyve done 400hrs and have been very well looked after by an old fella. Thanks again, Dean.
Rod would have meant the exhaust baffle plate Dean, they corrode through & spray water into the cylinders.
If I had those motors I'd change both baffle plates and both lower seals
(they do have a kit if the crank seal surface is bad).
They are 2 things that will kill those motors, especially on a cat where at idle they will sit low in the water.
Only other thing I can think of is make sure you don't lug them, they like to run free. 6000 WOT.
If you notice either one low on WOT RPM then it's time to check out why as leaving it will cost you money.
They make the best noise of any outboard.
rodneyk
18-03-2012, 01:54 PM
Hi Boys they were great sounding motors dean you lucky b////// to find a good cat again the XL/S will definatly help and if anything was to happen you will get home on 1 engine anyway have you tried to see if it gets up on 1 motor should go close i think . m8 used to run 115s on 7m haines cat now aka edencraft think there gone now but was a bit underpowered but did the job that was great to fish out of but then fuel was 40 cents per litre (hmmmm)
Dean1
18-03-2012, 02:27 PM
Hi Boys they were great sounding motors dean you lucky b////// to find a good cat again the XL/S will definatly help and if anything was to happen you will get home on 1 engine anyway have you tried to see if it gets up on 1 motor should go close i think . m8 used to run 115s on 7m haines cat now aka edencraft think there gone now but was a bit underpowered but did the job that was great to fish out of but then fuel was 40 cents per litre (hmmmm)Yeah Rod weve tried one motor alright and it doesnt plane. We came in on 1 motor 2 wkends ago from 65 klms out sittin on around 10 kts and it was pretty rough by then so a real pain. We planned on doing 2 days on water but ended up an overnighter. The next morning we started the motors up and 1 of the switches on the dash pushed right thru the dash and fell into pieces. I managed to stop the motor but could not get it to start again tried everything but didnt want to try hotwiring incase it somehow did something to the other motor. Bought 2 replacement switches on ebay pretty cheap. They are the push to choke switches so the plastic has gone brittle over the years hence why this happened. was going to add this to original post but thought it might throw it out of whack a bit lol
good to see someone else bust the 4/ myth.id definately do the inner sandwich plate and lower seals ,they should be good for another 6 years after that.the great economy will be the power to weight ,your not working them hard so they wont drink ,where the 60 4/ on the kc would be working pretty hard.
Dean1
18-03-2012, 07:16 PM
good to see someone else bust the 4/ myth.id definately do the inner sandwich plate and lower seals ,they should be good for another 6 years after that.the great economy will be the power to weight ,your not working them hard so they wont drink ,where the 60 4/ on the kc would be working pretty hard.Gday Opti, yeah i thought of the whole power to weight, but yammy 90's are alot thirstier. Must be that they are a 3 cyl motor as compared to these 6 cyl motors. These 560 Sharkys are pretty weighty so i thought theyd use alot more. Anyway will look into this plate. Cheers..
Jarrah Jack
18-03-2012, 08:04 PM
It really is unbelievable economy although I believe it. I had a 115 yami on a 16ft runabout, so power to weight was high but it drank close to 1ltr a klm.
Jabba_
19-03-2012, 05:08 PM
If they keep running and behave themselves im putting up with the 2 stroke fumes and oil coz we arent going to save much on fuel going to 4 strokes i cant see the point apart from reliability. we had the timing retarded to suit the fuel nowadays and noticed a power drop, man they were angry with full advance before we did this!
Thanks, Deano.
Deano, Decarbon your motor, and I bet my left nut you motors will run even better then they do now, and run a full synthetic 2st oil and your 2st fumes will reduce heaps
Dean1
20-03-2012, 08:29 AM
Deano, Decarbon your motor, and I bet my left nut you motors will run even better then they do now, and run a full synthetic 2st oil and your 2st fumes will reduce heaps
Yeah might try the full synthetic Jabba, have decarboned the motors when we first bought it thanks for heads up. They arent that smokey in fact less than my old 70 Yammys i think. Hope they keep on keeping on coz i love the growl and the torque :)
Noelm
20-03-2012, 08:41 AM
AAHH, the sound of a couple of 2 strokes in synch on a cat!! only thing better than a couple of 6 cyl Mercs is a couple of V4 OMC motors, now they sound sweeeeet! Those old tower of powers will run for years yet (with some luck) and indeed they were OK on fuel for their HP, I reckon they would make your old 4 strokes look positively sick at take off. I might add, I am not 100% convinved of full synthetic oil in an "old" motor, but some say it is OK.
Dean1
20-03-2012, 09:17 AM
AAHH, the sound of a couple of 2 strokes in synch on a cat!! only thing better than a couple of 6 cyl Mercs is a couple of V4 OMC motors, now they sound sweeeeet! Those old tower of powers will run for years yet (with some luck) and indeed they were OK on fuel for their HP, I reckon they would make your old 4 strokes look positively sick at take off. I might add, I am not 100% convinved of full synthetic oil in an "old" motor, but some say it is OK.Funny you say that noelm about the full synthetic because i was thinking the same. Been old motors i thought the old style 2 stroke oil would be a bit friendlier with these motors. Will research before going this way. Oh yeah these 90s would leave the F60s for dead no comparison at all actually i forgot how quick they get out of the hole the old 2 bangers, they launch a bit like a qtr miler :) Have to say i am loving this new tub the extra weight in the water makes for a more comfy ride they arent as flighty as the KCs and everything seems to be in slower motion at rest. The old Sharkys are truly a truckload of bang for your buck! Not saying KCs arent up there just both have plus's, minus..
Noelm
20-03-2012, 09:26 AM
yes, for the dollars they are a great boat, especially your model (the later ones) I kind of reckon that if they made them now, and fitted them with all the nice stuff we expect in a new boat, they would be very hard to beat, the Shark cat is very sparse in fitout, well less than sparse, really completely bare! but to compare them, my local dealer has a 5.2KC with older 60HP 2 strokes on it for 40 grand, you could buy a couple of good Shark cats for that sort of money, or even, buy one and repower perhaps, hard part is finding a good clean one.
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