K&B vs. OS 3.5cc outboards-which is better?

[Stingray 43]

I recently purchased a tunnel-hull boat. I hear great things about the performance of the OS engine and parts being easy to source.
I know very little about the K&B engines although other than they have less expensive engines available compared to OS.

I was also wondering if there were any scale head covers available for either engine. The only ones I found were made be Aeromarine and they are discontinued as they were for the previous generation K&B engine.

Also-does a tune pipe make a substantial difference on either engine and which ones work well?

All help is appreciated,thanks in advance.

[Ron Olson]

I've only run K&B 3.5 and 7.5 OB's but the O.S. 3.5 OB is quickly becoming the choice of more boaters. I did spend an afternoon with a local boater who has one and were getting his new boat dialed in. It's seems to be a very good engine to me.
DPI used to make a cover for the K&B's that looked like Mercury's but they're out of business. They are a rare find on eBay and bring a good price, I've heard they they have sold for $25-30.00 or more! I have two of them somewhere in my basement if I could only find them!

[bugfanatic]

Yeah & if this warm weather continues Ron can be out AGAIN with this local boater before February. Seriously Stingray, I looked long & hard to get an OS outboard that was NOS in the box. Remember, they stopped making them when I got mine. I figured the risk was worth it & it was. Now they make them again, so everything's readily available. In the early 90's I had a K&B & it was much harder to start, tweak, & maintain. I know people swear by them but I will never buy a K&B. (Although I have heard K&B were having quality issues which they have since sorted out.) My OS is trouble free & as Ron has seen it runs great & starts very easy. I can't answer about the pipe with the K&B but my old one had the exhaust exiting out of the lower unit if I remember right. The OS should take a tuned pipe no prob.

[Ron Olson]

Hi Dave! Yup, he's a O.S. owner that I was talking about. I know of another racer from Canada, Randall Thomas who could start his O.S. OB with just a flip of his fingers on the flywheel using no starter at all!
There are some aftermarket parts slowly coming out for the O.S. but there are a lot more for the K&B's as they've been around since the late `70's.

[CFRACR]

Regarding these two engines, I have owned both and have had many and still do. I would have to say that with proper care, they both can be very reliable and good engines in the long run. I will say that the O.S.'s seemed to wear out somewhat faster than the K&B's though. As for performance I never noticed enough difference to say one's way better than the other.

As for tuned pipes, you can put one on either. Yes, there will be a performance difference. There are a few available (silver bullet, J-pipe, Irwin), being popular, and a few others that may be contenders too. Some models are easy to adapt a pipe on with a header and a hanger. Some K&B models you have to modify the lower unit to hang a pipe.

My personal experience would say save the money and get a K&B if its between the two. Its a great sport engine, and with proper care will give you lots of service. If its high performance you want, Rossi has some high end power heads, but much more $$$.

[97TRAKIN]

K&B hands down. There are K&B engines out there running that are older than the people running them, FACT. I could start my old 3.5 with my hand.

[Stingray 43]

The boat I am putting this on is the Top Speed II. I have owned two deep-vees and I figured it was time to add another boat to give buddies something to play with.
I was surprised that the boat did not come with the stick on weights for balancing it. Anyone know where I can get some?

As far as the pipes go do some pipes work better for the O.S or the K&B or does any 3.5cc pipe release the fury?

I was wondering if anyone has speed checked this hull with a stock 3.5cc. Tower advertises it does over 50m.p.h.

Thanks for all the help guys.

[Ron Olson]

The stick-on weights should be available at most hobby shops, probably in the plane section. Prather and Great Planes both make them. The weights that they use for those little race cars that the Boy Scouts make and race (it's late and I'm brain dead at the moment because I can't think of the names of them) might work also.
If you look at the ad again, it can be tuned with a little work to hit 50 but realistically I'd say the mid-40's for most people. High percentage nitro plus a prop that the engine likes are a couple of the keys to getting 50 out of it plus getting it dialed in right. Getting any 3.5 OB tunnel over the 50 MPH barrier isn't easy, take a look at the current records and these guys are running high-dollar boats.

[Stingray 43]

The stick-on weights should be available at most hobby shops, probably in the plane section. Prather and Great Planes both make them. The weights that they use for those little race cars that the Boy Scouts make and race (it's late and I'm brain dead at the moment because I can't think of the names of them) might work also.
If you look at the ad again, it can be tuned with a little work to hit 50 but realistically I'd say the mid-40's for most people. High percentage nitro plus a prop that the engine likes are a couple of the keys to getting 50 out of it plus getting it dialed in right. Getting any 3.5 OB tunnel over the 50 MPH barrier isn't easy, take a look at the current records and these guys are running high-dollar boats.

Thanks for your help, if you happen to find any of those covers that you have please let me know.

[CFRACR]

The weights that they use for those little race cars that the Boy Scouts make and race (it's late and I'm brain dead at the moment because I can't think of the names of them) might work also.



You may be talking about soapbox derby cars?

As for the weights themselves, are they required for this hull. If you want speed adding weights is not helping. The hull trimmed out right sshould not need them. I personally have and run lots of different tunnels and have never added any weights. The only thing that I have had to do on a few hulls is move some weight to the Bow/nose cone to keep it from being so sensitive on slightly windy days. But this was done by moving already needed equipment, not adding more weight.

[Ron Olson]

Pinewood Derby cars! I just remembered the name!!!!! :D
Just about all of Jerry Dunlap's designs seem to need weight up front, 3-1/2 ounces and higher. I myself would rather use useful weight like a larger battery pack if room allows.

[CFRACR]

Yes exactly!!!!
On my 7.5 hulls I use c size packs for the extra weight that is needed. The longer battery time is a bonus. :D