Repower in dilemma!

[Mupster]

Here's my dilemma. In the next 12 months I'm planning on purchasing new motors for my 5.2 mtr Devilcat and my dilemma is power to weight with 2 strokes vs 4 strokes. On my cat the ideal best performing setup was the old 3cyl 2stroke 90hp XL Yamahas at 123kgs each, but now if I go 4 stroke the weight of the lightest 90hp XL is either of the new Mercury CT or Yamahas at 165kgs. 84kg difference is like having another person on board and being a cat a heavy bum weight is not ideal.

There's no doubt the fuel advantage is huge with 4 strokes so I'm not interested in 2 Strokes including the ETec's. Do the new 4 strokes have more punch than the old 2 strokes or are they on par?

The other motor I was looking at is the Yamaha F70 at only 119kgs but on the Yamaha website they have a sea trial report of a 18ft Sharkcat but they seem to be revving high and have high fuel consumption. The Devilcat is a better plaining hull than a Sharkcat so maybe this is an option but I've also read a lot of cat owner reports that the F70's work hard.

Is the F70 viable or should I except the 84kg disadvantage? If I do then I could even go the Mercury 115hp CT as it weighs the same as the 90hp CT!

Any comments or suggestions are welcome, good or bad!
Cheers.

[scottar]

Working on the non 2 stroke proviso, there is no real dilemma, you just need to find a work around. Does your hull have pods like some of the other cats? If so you may find a solution in increasing bouyancy with larger pods to counteract the heavier engines.

Do 4 strokes have more "punch" - they certainly have a different feel to their power delivery but these days it's not as noticable as it once was. That said at the end of the day, "x" horsepower is "x" horsepower and a small displacement 4 stroke like the Yamaha f70, as good an engine as it is, will be reving hard to push a heavier boat and thus be heavy on fuel. To get the best results for fuel economy from a four stroke, picking the highest horsepower your hull can carry to allow a good cruise speed at roughly 3500 rpm is a good basic rule of thumb. Pretty much all the fuel curve test results I have seen have economy falling away from this point give or take a few hundred rpm. As such, the 115 Mercs would be my pick of the options given provided they fall within hull ratings and you can find a way to carry the extra weight.

[Lovey80]

If Pods aren't an option, and I would probably do this first any way. Consider moving your batteries forward to underneath the drivers seats. I assume they are close to the rear of the boat? Naturally you will have to probably account for the extra distance the power has to travel to get to your engines and go to a larger gauge wire to your engines to account for the extra distance.

[Flex]

I own the sharkcat that did the trial with the f70 yamaha's on it. Don't get the f70s ! Revving their tits off just getting to 20 knots.
They are a very tiny motor, they will make your boat underperform a bit. They will be especially annoying if you travel long distances offshore.
I sold the f70\s and whacked on a set of f115 yamaha's. its bum heavy bit new pods are going on very soon.
If you say 90hp was the best performance id be looking at that size minimum.. Especially in the Suzuki's as they tend to build what I call 'sportier' engines than the older Yamaha and mercury. although I cant say ive experienced the new f90/f130 Yamaha performance. The new high displacement mercs seem like an excellent and well thought out engine design. especially from a maintenance perspective. Although I have heard through the grape vine they are a bit thirsty through.

[MadKat]

Hi Mupster

I have a 5.2 Kevlacat and recently re-powered with 90 Suzuki, Not sure if the Devil Cat needs XXL legs but you will find the Suzuki the lightest on the market and also extremely fuel efficient.

I did however put larger pods on to assist with the extra weight.

[Mupster]

Thanks for your response all, sounds like what I was quietly thinking in my head and that's the F70 are duds for a cat. I love the minimal maintenance of the Mercs, that's hard to discount.

I have alloy Clearwater brackets on my cat that change it from Long shaft to Xtra long shafts, so maybe I could try the extra weight and see how it works and if it's not good then I could change to pods. Devilcat's sit higher out of the water than Sharkcats because of the higher tunnel so that might help too!

Suzuki are updating their range at the moment and next week is the Melbourne Boat Show so I'm going take the magnifying glass to them all!

[mace01]

Not sure about on a cat, but the Merc 115 CT has unbelievable low end torque. Not sure of the exact torque curve, but it holds (used to when I had the boat), my 5.3m Cruise Craft at cruise speed (say 20kn) at ~3200 rpm all day with very little fuel. Mat.

[billfisher]

I don't quite follow that if you are worried about power to weight (a genuine concern when re powering old boats with four strokes), why would you want to rule out Etecs? Their fuel economy is comparable to 4 strokes and the have a much better power to weight ratio.

[Skusto]

Looking at repowering in the future as well, 4 strokes will never have the low down grunt of the old two strokes.

Have priced up the 90 suzukis, 115 mercs 90 mercs 90 yammies and 90 etecs and to be honest there bloody expensive! No to mention the on going yearly service fees of $1,000.00 a year.

I'm starting to think that it may be better to see if they have a clearance sale on the carbie two strokes towards the end of next year since they will no longer be available and just chucking two more on for probably half the price.

$15,000.00 gets you a lot of fuel!

Even for the extended long trips could always just get fuel bladders to run on first to give more range.

Decisions decisions.


Sent from my iPhone using Ausfish forums

[Mupster]

I don't quite follow that if you are worried about power to weight (a genuine concern when re powering old boats with four strokes), why would you want to rule out Etecs? Their fuel economy is comparable to 4 strokes and the have a much better power to weight ratio.

I don't want to talk down the Etecs and offend anyone. I know a dealer who has quietly handed back his dealership because he's had enough of chasing his tail fixing them. Yes owners have had great trouble free ownership and put big hours on them, but the horror stories are true and I'm just not prepared to hang my arse out there after spending 30k on to new motors. Great motors great performance but not for me sorry!

[Mupster]

Looking at repowering in the future as well, 4 strokes will never have the low down grunt of the old two strokes.

Have priced up the 90 suzukis, 115 mercs 90 mercs 90 yammies and 90 etecs and to be honest there bloody expensive! No to mention the on going yearly service fees of $1,000.00 a year.

I'm starting to think that it may be better to see if they have a clearance sale on the carbie two strokes towards the end of next year since they will no longer be available and just chucking two more on for probably half the price.

$15,000.00 gets you a lot of fuel!

Even for the extended long trips could always just get fuel bladders to run on first to give more range.

Decisions decisions.


Sent from my iPhone using Ausfish forums

Good point but I'm not sure the 2strokes are half the price of the 4 strokes, even at run out time they'll still be up there in price. There won't be any large stock pile to sell off here in OZ, stock levels will be low. There is still a lot of countries around the world 2 strokes will still be sold in.

[billfisher]

I don't want to talk down the Etecs and offend anyone. I know a dealer who has quietly handed back his dealership because he's had enough of chasing his tail fixing them. Yes owners have had great trouble free ownership and put big hours on them, but the horror stories are true and I'm just not prepared to hang my arse out there after spending 30k on to new motors. Great motors great performance but not for me sorry!

I have an old boat too with a 1992 90 hp 2 stroke. One day I will have to re power and I
think that there may not be any choice but to get an Etec given the weight issue with 4 strokes. I wonder what the actual failure rate is with Etecs? It's not like 4 strokes don't have problems either and if something goes wrong internally it will not be economical to repair them (some have terminal corrosion problems too).

Also I'd take with a grain of salt what any dealer says about a brand he is not selling. It is common practice for them to rubbish other brands.

[Mupster]

I have an old boat too with a 1992 90 hp 2 stroke. One day I will have to re power and I
think that there may not be any choice but to get an Etec given the weight issue with 4 strokes. I wonder what the actual failure rate is with Etecs? It's not like 4 strokes don't have problems either and if something goes wrong internally it will not be economical to repair them (some have terminal corrosion problems too).

Also I'd take with a grain of salt what any dealer says about a brand he is not selling. It is common practice for them to rubbish other brands.

I've known this dealer for along time and I feel his pain and know his decision is legitimate. He has sold two brands side by side for a long time too so it's not just the typical jumping ship to another brand and then bag the other.

As for terminal corrosion problems in 4 strokes, I agree they have all had this problem, each and everyone of them but some have solved it and others have tried better methods that only time will tell.

[hainsofast]

2 bangers all the way

[Flex]

Also consider the range at which you fish and the type of fishing you do?
Do you troll all day for billfish?
Are you running 300km round trips when you go out?
do you drift fish a lot?
All of the above will require a decent 4 stroke or you simply wont have the capacity. How big are your fuel tanks?

If your only running 20km out and anchoring up, then investment in brand new expensive 4 strokes may not be the best financial choice. buy a set of second hand 2 strokes possibly for the best option from a pure cost perspective.

Lets not forget the added enjoyment of a nice quiet set of 4 strokes off the back.

as for etecs, I do rate them very highly.
I owned a 175 for a while. Id never own one for offshore boating though. The oil cost is crazy! Id often use 300l to 400l of fuel in a trip for roughly 6-8litres of oil. At $80 for a 4l bottle that's over $150 ontop of fuel each time.
Added to that, If you go away to remote places fishing for a week and snag a good spell of weather often the small towns don't even stock the etec oil.