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Can an RL24 be successfully powered by a 4hp?
Hi All, I am considering replacing my smokey, noisy, two stroke, 6hp for a four stroke 4hp. Can anybody share their experiences of powering an RL24 with a 4hp? So far, the 6hp seems to push the boat along nicely at half throttle. Just a bit concerned about how the 4hp would go pushing through less than perfect conditions. Any comments would be greatly appreciated. Thanks Geoff
Geoff Watson7-Jul-2013    Edit    Delete 
Re: Can an RL24 be successfully powered by a 4hp?
In a word, yes. It also means that the vessel doesn't have to be registered, but there are limitations with that size motor. If you have to make a lengthy passage against wind, tide or waves, you will wish for something bigger.
We use a 4hp Tohatsu for occasions like the Bay to Bay race in order to keep weight down a little. It works fine. However, I can remember an occasion heading down the Great Sandy Strait battling a 20-25 knot head wind and an incoming tide when we were struggling to make 3 knots and the odd wave set would almost stop us dead. I wished for a bigger motor that day. And that's in an area designated smooth water. I have also tested a 2.5 hp motor. It could do 5 knots in dead smooth water with no wind.
My recommendation would be 5hp or better and I wouldn't rule out 2 strokes. Smoke emission is often a by product of the oil used. Valvoline is up there with the worst of them in that regard, wheres some of the synthetic based oils burn a lot cleaner.
Mike7-Jul-2013    Edit    Delete 
Re: Can an RL24 be successfully powered by a 4hp?
Thanks for the info Mike. As it happens, I do use Valvoline Oil at 50:1 in my 2 stroke. What would you recommend to reduce smoke emission?
Geoff Watson16-Jul-2013    Edit    Delete 
Re: Can an RL24 be successfully powered by a 4hp?
Yamaha Lube at 75:1 mix is low smoke.

These days the special outboard oils are not better than other two stroke oils. Any two stroke oil rated JASO FC or FD oil is good at 75:1 mix. I've started using the Castrol two stroke on my scooter and will use it on my outboard when I run out of Yamaha Lube.

Use a proper measuring system for the oil, the bottles the oil comes in is not accurate enough.
Greg18-Jul-2013    Edit    Delete 
Re: Can an RL24 be successfully powered by a 4hp?
I have been using a locally manufactured product, Synforce, and am happy with it. I believe Castrol is also a good product.
Any oil rated TCW3 should be OK; this is the standard recommended by outboard motor manufacturers for water-cooled 2-stroke engines. I feel that the manufacturers of the motors and the oil blenders know more about this than I do bearing in mind that like averything else, oil can be produced with a price-point in mind. I know of people who use the same oil in their air-cooled 2-strokes and in their outboard motors. I am always a little wary of people who know more than the manufacturers.
Mike22-Jul-2013    Edit    Delete 
Re: Can an RL24 be successfully powered by a 4hp?
Mike the TCW3 oil blends have changed recently with some additives removed because they might damage catalysts in exhausts. Originally the big issue with TCW 3 oils was their low ash which was essential for the heavier duty watercooled marine engines.

Over the past 20 years other two stroke oils have improved dramatically with the newer JASO standard providing a much better oil performance guide than the other standards. The new two stroke oils have low or no ash andthe JASO standard allows for both lubrication performance and low smoke performance. JASO FC and FD are the higher performing low smoke oils which should work well in any small two stroke outboard.

I've been using 75:1 mix ever since Castrol made the Biolube 100:1 mix oil for ordinary 50:1 mix outboards. I could not get to using 100:1 mix so I settled on 75:1 mix and Ive not had any issues in the 20 years I have used the synthetic or premium oils at 75:1 mix.

Remember Yamaha and Suzuki have had 100:1 mix engines for a very long time.
Greg 23-Jul-2013    Edit    Delete 
Re: Can an RL24 be successfully powered by a 4hp?
You should read this article about oils and oil ratios:
http://klemmvintage.com/oils.htm
While it may be talking about different engines, the ratio of premix vs RPM is universal.
Daveinet25-Jul-2013    Edit    Delete 
Re: Can an RL24 be successfully powered by a 4hp?
Dave, a good article and very relevant.

The article does not mention the JASO standard that now covers many of the gaps they mentioned in things like low smoke performance.

Fortunately our outboards are such low performance engines that they last a very long time compared to the 120 minutes they were using as an example on vintage race engines.

To explain that I am not a complete novice my current road scooter I use for commuting has a worked 70cc two stroke engine producing over 10hp at over 10,000RPM with lots of good oil for lubrication. It would not be up there with their race engines but it does about 10,000km a year hauling my substantial butt to work and back and it would not survive without the best lubricants.

I am still happy to use 75:1 mix with the better oils on my little outboard that is measured at 4,800RPM flat out.

Remember Yamaha and Suzuki sell outboards with 100:1 mix.
Greg 25-Jul-2013    Edit    Delete 
Re: Can an RL24 be successfully powered by a 4hp?
Geoff,

On Chill Ouat We us a 5 hp merc . This motor has a top fuel tank and a remote tank as well. This pushes the boat along fine in all weather. The 5 hp is the Sam size as the 4 hp.
Under the class rules you need to have a motor the has a weight of 20 kgs min weight as well.

Dave
Dave pullin1-Aug-2013    Edit    Delete 
Re: Can an RL24 be successfully powered by a 4hp?
Thanks Dave and all who commented. I am going to borrow a 4hp and give it a try. In the mean time some experimentation with oils might allow my 6hp to kick its smoking habit!
Geoff Watson1-Aug-2013    Edit    Delete 

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