Suzuki DT9.9

Come in, spinner

Through the 1970s and 80s, 9.9hp outboards were prevalent on 12ft tinnies. These outboards were considered by many anglers as being the way to go when more than 6hp was needed because they were still reasonably light to carry while providing a lot more power. As most of us know, the worse thing you can do is under-power a planing hull!

In the 90s, 9.9hp outboards took a back seat to 15s as 12ft tinnies grew in beam and hull depth. Most anglers reasoned that why buy a 9.9 when a 15hp outboard weighed the same. And in most cases 15s cost only a little more to buy than their 9.9hp counterparts. Outboards such as the Tohatsu 18 provided even more power for the same weight without going to the bulk and considerably greater weight of a 20, which in some cases were a de-rated 25hp engine.

But providing a 9.9hp engine is correctly matched to the hull loading (occupant, safety gear and fishing tackle weight) and planing surface area, it can provide almost as good performance as that of a 15hp engine. Sure, the top-end speed will be down but, because the engine develops almost as much torque, it should be about as quick out of the hole.

An example of this is the Suzuki DT9.9 I tested on a Blue Fin 3.8 dinghy in January. Because this bulky 12.5-footer has a shallow deadrise aft and a relatively large planing surface compared to the hull length, it performs well with a 9.9, which is less than 40 per cent of the rated maximum power. For the test we limited the hull load to two adults, bringing the total to 330kg and well within the loading this hull is designed to handle. Had we a third adult aboard, we would have had to have fitted a 15 to 20hp outboard, particularly if the optional flat floor had of been fitted.

Spinning the standard eight-inch pitch Suzuki alloy prop the 9.9 was slightly underpropped but still returned reasonable cruising and wide open throttle performance. It trolled us at 3.1km/h, using 0.6lt/h at 800rpm. It planed us cleanly at only 17.3km/h and 3600rpm using two-thirds of the throttle to get us out of the hole before throttling back. Cruising at 4700rpm, it averaged 23.8km/h using 4.1lt/h. No prop ventilation occurred through full-lock figure of eight turns at these revs. The WOT averages were 33.1km/h and 6.3lt/h at 5700rpm; so when additional gear such as a well-loaded cooler is carried aboard the revs would still be at the upper end of the recommended WOT rev range.

The demo 9.9 started easily, hot or cold, and despite running on a 25:1 break-in mix of ULP and Quicksilver TC-W3 oil, smoke appeared only below 2000rpm. The side gearshift was reasonably easy to operate and the long tiller arm was comfortable to use over longer distances. Vibration levels across the rev range were pleasantly low for a twin cylinder carbie two-stroke, although at or near WOT the Suzy became slightly raucous due to carbie induction roar.

Powerhead access is very good and a nice touch is the large bowl-type fuel filter. The spark plugs and ignition timing advance linkages are easy to clean and adjust. Overall, the 9.9 is well finished, although a rubber seal on the bottom of the upper cowl would prevent damage when it’s removed for powerhead access.

Recommended servicing intervals are every 50 hours or six months after the initial 20-hour service. The waterpump impeller should be replaced every 100 hours. However, as the impeller runs in a stainless steel liner, it will probably last well past this mark.

The DT9.9 is rated ‘High Emission’ under the Australian OEDA emissions compliance scheme and has a two-year warranty for recreational applications.