Excel SD360 & Mercury EFI 15HP Review

Steve509926 · 14 August 2020, 20:08

Second day out in the SIB and I really wanted it to be as good as the first (see previous post - Newbies Maiden Voyage – Excel SD360)
Primary objective of the day was to set the AV height and fix/bolt the outboard to the transom.
I knew from the previous day that the AV was too low in the water and the outboard needed lifting. I had brought 4 different thicknesses of packing with me 5mm, 10mm, 20mm and 25mm wood blocks (got to thank Fenlander for that tip)
I clamped and tethered the OB to the transom using the thickest packing – 25mm, which was at the limit for the clamps to be fully on the transom. I loaded up the SIB the way it would be used the vast majority of the time – Wife, dog, full 12ltr fuel tank, 2 x 6Ltr extra fuel containers, 2.5kg anchor + chain, ropes, wet weather gear- after all it is The Lakes!, picnic and a few other bits & bobs.
Out on the water it didn’t take long to realise that the AV was too high. The prop burped, bubbled and farted on every revolution, so back to the slip we went. Fitted the 10mm packing and it was the complete reverse, not a sound from the prop no matter how fast we went or how tight we turned. To cut a long story short, 20mm packing is probably the best compromise I came to, no burping or bubbling when straight lining and only a little bit of bubbling on sharp turns. Back to the slip, drilled through the bottom bolt holes on the outboard and through the transom, in with some Sikaflex 291 and bolted the OB to the transom.
Off we went for a day’s exploring on Ullswater. Slight breeze probably 6 mph from the west, and little “wavelets” 10cms or so - important to note for a later observation.
The SIB very quickly came up on the plane the GPS indicating a speed of 5.5 knots. We cruised at this speed for a couple of miles down the lake on the far side from the road. The outboard purred along nicely, quiet, very little vibration and easy on the hand due to being able to set the speed using the “Throttle grip friction knob”. The tiller on the Mercury not only has the throttle, but it also houses the gear shift lever and the throttle grip friction knob, in my opinion it is worth paying a little extra for these two features.
We came to a very quiet wide bay which just asked me to open up the throttle a little. Great acceleration from both the SIB and the OB, no hesitation or twitching left or right. We were soon at full throttle, the GPS showing 15.8 knots. The SIB was rock solid, the Airdeck hardly moved. However turning is a little different than I was expecting. It is not a positive turn; it’s more like a slide or drift. I slowed to 9 knots (speed limit on Ullswater is 10MPH) and repeatedly turned the SIB to the left and right. Again it is a slight drift rather than a positive turn but providing the speed is kept constant or even increased out of the turn slightly it isn’t a problem, in fact I think it helps with the stability of the SIB.
The rest of the day was spent sedately cruising and enjoying the beauty of Ullswater and the surrounding fells. Was it as good as day one, it was better.
On day three, we were joined by some of our family. The day was beautiful, sunny, still and the lake was like a mirror reflecting the fells on the surface, not a ripple to be seen. I couldn’t wait to get out on the water.
As Glenridding was so busy, I had decided for us all to go about 3 miles down the lake on the far side for a picnic, it would take three trips, but it would give me a chance to test the SD360 and the OB with different loads.
On the first trip I loaded up exactly as day 2, wife, dog etc. Set off as before, but something was wrong. The SIB was different, even at 8 knots it was struggling to get up on the plane, so I stopped mid lake and checked everything I could think of. Transom wheels – up, OB fine, load evenly spread, everything looked as it should. Set of again, exactly the same, it was like the SIB was “glued” to the water. I increased the throttle a bit more and eventually we were on the plane. But then the Airdeck which had been as solid as a rock on day one and two, started to move, a bulge from the bow to the stern. Two or three times this happened until suddenly the SIB came off the plane and the prop struggled to grip as what can only be described as a big bubble of air escaped from under the stern. Concerned a little, I headed back to the slip. After checking and double checking that everything was as it should be, we set of again. By this time the perfectly still surface of the water had little “wavelets” on it as a light breeze had picked up.
Perfect, the SD360 was very quickly on the plane and everything was good again. The Airdeck was rock solid, no movement what so ever. Why had it happened? The only explanation I can think of is the surface of the water was so smooth that the SIB struggled to break free of the surface tension causing pockets of air to build up under the hull. I am pleased to say it never happened again.
After dropping off my wife, dog and picnic I returned to Glenridding solo. A different experience was had; I definitely need to buy a tiller extension. I didn’t feel comfortable at full throttle with the bow riding so high and I couldn’t sit forward enough to even the load.
The second trip was uneventful, very smooth, very steady two daughters and two grandchildren on board made sure of that.
The third trip back down the lake would be the tester. With three hefty men, camp chairs, fuel and a pushchair in the SIB – probably close to 400KG, I was expecting it to handle very differently, especially at speed. It didn’t appear to make any difference to the SIB’s handling what so ever. It was still stable, responsive and felt as solid as a rock. To get on the plane took a little longer, but we are only talking a second or two and top speed on the GPS clocked at 15.1 knots with a slight breeze against us.
In conclusion I think the Excel SD360 is an ideal family friendly SIB. It is a bit heavy but it is just about manageable for one person to unpack and pack it away again, especially if you pack the Airdeck, seats and oars separately. In my opinion it is stable, solid, responsive, spacious, and good value for money. I would not wish to go any smaller than the SD360 and although I would like to have a bigger SIB like the Volaire 390/430 I would then need to trailer it which towing a caravan is impractical.
The 15HP EFI Mercury is, again in my opinion, a good match for the SD360. Just about manageable weight wise to lift in and out of a vehicle, powers the SIB well, brings it onto the plane relatively quickly and very importantly doesn’t appear to be affected to much when the load in the SIB increases. I think a 9.8HP OB would be slightly underpowered for what I want to use the SIB for conversely I think a 20HP OB would be overpowered for what I will be using the SIB for.
Please bear in mind if using this review to help you come to a decision when buying a SIB/OB, I am a newbie, this is my first SIB and my first OB so all of the above must be read on that basis. I am also relatively fit, healthy and quiet strong so when I say things are a bit heavy, some may disagree and say they are very heavy or impossible to lift.
I’d like to thank everyone on this site who helped me come to the decision I took when buying the SIB/OB, your input was invaluable.

jeffstevens763@g · 14 August 2020, 21:46

Great write up Steve

Fenlander · 14 August 2020, 23:12

Yep... really great to hear in so much detail how you got on. All folks are different in what they use a forum for and that's fair enough but sometimes after so much discussion of which outfit would suit we get feedback that has us wanting more detail. But you've really upped that balance.

The skid turns of a SIB do take some getting used to and in some ways can catch you out more at slow speed and in close proximity to other boats or pontoons/piers etc. There is not much to grip the water and steering is only really achieved by small bursts of throttle... which is not always what you want close to others. At least they bounce off things.

Re the one experience you've had of prop ventilation associated with the air floor other than the usual "was the floor/keel fully up to pressure and re-checked once in the water" comment this somewhat goes with the territory of flat air floors. The only thing I've found that affected this was a change of prop design. But it's a bit unpredictable as to the the results seen and at up to £100 for a prop you can end up spending a bit chasing a small return.

I can't remember if we discussed rev counters? It would be interesting to know your maximum speed revs... and the existing prop pitch. If you are not making advised maximum revs at maximum speed with your usual load then dropping prop pitch is a good idea anyway and may assist with the occasional ventilation.

Also I wonder if your top speed is a little down on what I'd expect which could be down to prop pitch... although I'm first to admit this is not the ultimate purpose of SIBs... they are not speedboats. Our lightweight (44kg as opposed to yours at 58kg) 3.6m air floor Zodiac made a whisker over 19kts two up with a 15hp.

Most of us on a normal SIB find a 20mm shim about right... I say normal as the hull design of the Aerotec model like mine can mean you need to go nearer 40mm or more with some outboards which entails greater mods.

Steve509926 · 14 August 2020, 23:38

Hi Fenlander, I do have a tacho but I didn't take note of the revs when we had maxed out at top speed.
I will be back out on the water in a few weeks time, providing the weather gods are kind, off to Kingsbridge in Devon. So I will note the revs at top speed then.
Will the pitch be stamped on the prop?

Fenlander · 15 August 2020, 00:22

Usually the pitch will be stamped on the prop boss or back of one blade... something like 9.25 x 10 with 10" being the pitch. Or perhaps just 10P. And sometimes just a part number you can Google.

I'd expect you have something between 9" & 10" pitch.

Steve509926 · 15 August 2020, 11:26

Hi Fenlander,
Took a look at the prop this morning and it is a 9.25x9P
If my understanding of pitch V's RPM is correct, with my OB I would be aiming for an RPM of 5950 (mid range) at WOT
If the RPM is below 5950, would need to change to a prop with a lower pitch? Say a 9.25x8 or 9.58x7?

Fenlander · 15 August 2020, 14:00

9" pitch is a good start. On my 15hp Mercury/Mariner 2-strokes it covered all my loading situations and I kept to that pitch.

Had you been fitted with a 11" or 12"... maybe even a 10"... I'd have been thinking a drop might be needed but with a 9" I'd expect when you see some rev readings they should be thereabouts.

Steve509926 · 15 August 2020, 14:04

Thanks for that. I'll check it out in a couple of weeks time when I'm in Devon.

Fenlander · 15 August 2020, 14:11

>>>when I'm in Devon.

Not jealous at all!

Steve509926 · 15 August 2020, 14:37

Yep, I'm really looking forward to it. Booked well before I got the SIB, I was just going to take the kayaks but now I've got something a bit bigger to play with.
Planned 3 launch sites, Dittisham, Hope Cove and South Sands at Salcombe, depending upon weather, tide and car parking!
Are there any other launch sites you could recommend.

Jasierock · 22 August 2020, 16:33

Great post Steve. This is just the sort of review us newbies need when trying to decide which SIB/motor to buy. I'm torn between the Excel SD 360, and Honwaves T38 and T40. As has been said on here many times, its all a matter of compromise. Mine will not be used all that frequently as like you I live in West Yorks (Silsden) which is a bit far from the sea!

Steve509926 · 22 August 2020, 20:26

Thanks for that. Don't know if you've read my previous posts, they may help you in your quest to find the SIB you are looking for. Also don't be shy to ask questions there are a lot of very helpful, very experienced guys on here, they helped me a lot.

Steve509926 · 22 August 2020, 20:30

By the way, I have nothing against West Yorkshire, after all my son in law hails from Pontefract, but I'm a proud Lancastrian

who lives in West Lancs.

Jasierock · 22 August 2020, 20:54

Ha! Sorry, I mis read your location as Apperley Bridge which is about 8 miles from here!!

smallribber · 23 August 2020, 06:57

Steve

Very informative write up and I and glad you are enjoying your sib. On the occasion you had the issue could you have caught something on the leg of the outboard like a clump of weed or other debris. This can cause issues.

I was wondering what the mat with holes in is on your air floor that looks very good and I would like to get some for my set up

Steve509926 · 23 August 2020, 08:22

Hi, I checked for anything wrapped around the prop and it was clear. I do believe it was water surface tension. I will only know if it happens again in the same conditions, but it's very rare that the Lakes are that mirror flat.

The floor mats are Sunncamp multi purpose Eva floor mats. You can get two types, with holes in or without holes, obviously the holes allow water to drain through. You can buy other makes at B&Q, Halfords. I think they are about £14 for 4.
I put them down to protect the floor and so that the dog doesn't slip.