Ceasar Surfcat engine choice

[Jacob555]

I've finally found and bought the air entrapment SIB I've always wanted: a Ceasar Surfcat.
I looked at a lot of forum threads and it's the ideal compromise for me; not as wet as a Zapcat or Zapcat clone, but a bit more performance focused than a Zodiac Futura- one of which I very nearly bought.
Interestingly, (or not!) my plan had been to put a console and wheel steering etc. on one of these sort of boats, complete with filled in transom and elephant's trunk balers so i don't need a wetsuit to drive it.
By a bizarre twist of fate, the one I have bought already has these mods (apart from the balers). So I'm clearly not the only person out there with such odd fantasies!
(I a,use boats a lot on my own- and the console gets the drivers weight further forward- and b, dont like sitting on the floor anyway). I have no interest in racing the boat. I just want something light, economical but not riduiculously untennable in any kind of chop. Crucially though I need to be able to hand launch it over a mixture of grass and shingle. Basically I want the closest thing to a RIB in terms of seakeeping, performance etc. BUT with awesome fuel economy and hand launching on wheels I can take with me.

The overall plan is to be able to hand launch with fold down transom wheels as I live very close to a beach. The wheels I have in mind are a system to my own design which fold down on L-shaped legs under the boat placing the wheels exactly under the balance point of the boat. Not like the traditional transom wheels where the boat can feel awfully heavy at the bow because the wheels are far too far aft. They will also have balloon knobbly tyres (of the sort more popular for beach catamarans) to help reduce sinking on the shingle. when not in use they will fold back up against the transom like an A-frame, albeit an A-frame with bloomin great big wheels at its top corners.

Anyway, it's current engine is a Honda BF30D, which with PTT, elec start etc. is V heavy. It's also probably more power than I need.

I have another option of a Yamaha 50 Autolube, but it's longshaft, so that option depends on the rather long shot of getting the shortshaft conversion bits for reasonable money. It also feels about the same weight as the Honda 30 as it also has PTT and elec start, and, of course will gobble fuel- so again not my preferred option. Also much more power than I will need. I might keep the motor though to pop on for some more engaging trips but with conventional trailer launching.

I think my best route will be to sell the Honda (I don't like Hondas due to their weight and tendency to dissolve in salt water- although this one appears surprisingly mint) and get something more suitable (ie., lighter) for my needs.
I want the boat to be stupidly economical but not lose all its charms and abilities.

Does anybody have experience of these sort of boats with 25hp? 20hp?
economy? Launchability?

For the economy I think i will have to go 4 stroke, despite the fact that I love/ understand/ can often fix Yamaha Autolube 2 strokes because I have ALWAYS run them. I won't be buying new- but probably can stretch to something 3 or 4 years old.

So what fits the bill? What do people think is the lowest power I could get away with and still plane properly?

I guess i need the lightest 4 stroke on the market. I note that Suzuki have often claimed this. Would this claim be correct at this sort of engine size? If i go to this size it won't need power trim or elec start, but I'd still like to run it with remotes and the console.

Or am I being over enthisiastic on the fuel economy thing? perhaps a Yamaha 30 Autolube would keep me happily still in the Yam 2t club and actually be bearable on fuel? I know I used to lift one on and off a boat and into and out of the car boot with litle trouble. It wasn't a pleasurable experience but was doable.

[lukewhiting]

My friend used to own a gemini gsx 420 (very similar just slightly bigger) with a 50hp tohatsu on a tiller.

Great boat with that engine, super economical, light enough to hand launch. Got around 40mph aswell!

Would defiantly only consider using it with a short shaft engine. Wouldn't want to go less than than 25hp even with a lightly loaded boat aswell in my opinion

[Roflhat]

I had a surfcat for about 4 years before moving to a thundercat. I had a tohatsu 30 on the back, which was fine with a light load but these boats really are designed to have a short shaft tohatsu/yamaha 50 on the back. With the 30 and a 13p prop it would top out at around 34 knots. With the 50 around 41 knots, and then with a big cleaver prop around 48 knots.
The tohatsu 30 is a 2 cylinder and was very light, really a very good engine for it. My mate still has the engine, he might be selling it if you're interested.
If you're going for a yam 30 3cyl then I would just get a 50. It's good to know the power is there if you need it, even if you spend most of your time cruising around 30 knots or so. You can't drive it without a smile on your face

Once you've tried it with a 50 you'll realise the way it works, you get much more air under the boat and it lifts further out of the water - less drag, more lift. The fuel economy between the 30 and 50 really wasn't too different, probably due to this and the fact that with a 30 I spent 90% of the time at WOT, compared to probably 40% or so with a 50. Mercury also make a 55 seapro short shaft, or you could try and find a yamaha 70ces. What I would say is stick with short shaft, a long shaft will either be far too deep in the water or too high in the air, both of which will ruin the boats magnificent handling.
I always wanted to try jetski style steering on mine, maybe stick a yamaha 90 on the back...

[Jacob555]

It sounds like I might need to get a short shaft leg etc. for my Yam 50 and consider trailer launching it for the time being rather than my fold down wheels/ hand launching idea. It's a good engine which I've had for years, so I'd be much more inclined to adapt this one with short shaft bits if I can get them, than sell it and get the same engine with a short shaft. Plus sods law dictates that my next boat will need a longshaft 50 if i sell that motor.
I'm not considering using a longshaft engine on a surfcat.
With a cleaver prop you will have been able to lift it considerably on the transom? Indeed they are designed to run with only the bottom sweep of the prop in the water aren't they?
So did that entail further mods (such as low water pickups, leg exhausting, props that need finishing/ balancing etc?) I don't want to get involved in all that.

Do you know if my Yamaha 50 takes the same prop fitting as a Tohatsu 50? Im guessing if it is the same I can get an ex Zapcat/ Thundercat secondhand cleaver props. Something that's 2 knots too slow for somebody's racing boat would be perfect for me.

[Roflhat]

You can happily run cleavers/choppers on standard engines. There's lots of mods you can do if you like, but they're not required. Yeh you'll want to lift the engine a bit to get the revs out of them if they're higher pitch. Around 18p is ideal for surface piercing props on standard engines, or 15p with a standard "bunny" prop.

Yeh all the yamaha/tohatsu 13 spline props are interchangeable. Mercury 13 spline props also fit, they make the best cleavers and choppers, as well as some good bunny props. A good all round prop is a 15p vengeance from mercury. There's plenty props kicking about, one that's 2 knots slower may be better for acceleration, and what works on one boat might not work on another. I've got 6 different props for my thundercat and still after more!

Have a look at Ron Hill propellers, they're not bad if you're working on a budget, although they quite often need balancing to stop them vibrating. If you can get your hands on a genuine merc prop it's good to go out of the box.

The yamaha 50's are very strong engines, very popular in the modified class. You can snip the limiter on them and you're good to go

[prairie tuber]

I'll concur with what the other guys said about there being tremendous benefit that 50 hp will provide over a 30 hp.

With regard to the transom mounted launching wheels, I would not recommend that route. I'd suggest either a cart/dolly with 4 or even 6 Wheeleez style balloon tires, or simply getting some inflatable beach rollers (there was a great thread on these in this section very recently).

[Jacob555]

Originally Posted by Roflhat

You can happily run cleavers/choppers on standard engines. There's lots of mods you can do if you like, but they're not required. Yeh you'll want to lift the engine a bit to get the revs out of them if they're higher pitch. Around 18p is ideal for surface piercing props on standard engines, or 15p with a standard "bunny" prop.

Yeh all the yamaha/tohatsu 13 spline props are interchangeable. Mercury 13 spline props also fit, they make the best cleavers and choppers, as well as some good bunny props. A good all round prop is a 15p vengeance from mercury. There's plenty props kicking about, one that's 2 knots slower may be better for acceleration, and what works on one boat might not work on another. I've got 6 different props for my thundercat and still after more!

Have a look at Ron Hill propellers, they're not bad if you're working on a budget, although they quite often need balancing to stop them vibrating. If you can get your hands on a genuine merc prop it's good to go out of the box.

The yamaha 50's are very strong engines, very popular in the modified class. You can snip the limiter on them and you're good to go

Thanks for your help on this. I'll be back here again to talk props etc. once I've got an engine sorted for it as I can see you are a lot further along the road than i am when it comes to optimising these boats.

[Roflhat]

No worries, keen to hear how you get on. Have you got any photos of your setup?
This is a good place for info too - Thundercat Inflatables Forum