Outboard Power

[M Cuff]

I have just upgraded my dinghy to a second hand 2.7m Waveline GRP rib replacing a seago 265 slatted floor dinghy. I have a Mercury 3.3 2-stroke which is brilliant and light but I was hoping for a bit more grunt and to get the rib on the plane. I recently acquired an old Suzuki dt-4 which starts on the button and has the advantage of f-n-r gears and external tank if needed. It has recently been in my outboard motor place as it wasn’t watering and has had a good check over and is running nicely. However, when I put it on the boat it wasn’t as powerful as I was expecting and about the same speed as the Mercury. Should I be expecting more oomph? Am I missing something obvious?

 

[B27]

You're missing about 6 horsepower for easy planing and good power to overcome wind and chop etc.

The DT4, like all outboards, needs to (roughly) reach max revs to give its full power, so it might benefit from a different prop. Also be careful of weight distribution, in my old GRP dinghy, we could plane with 4HP if we used a tiller extension to keep our weight forwards.

 

[Graham376]

I have just upgraded my dinghy to a second hand 2.7m Waveline GRP rib replacing a seago 265 slatted floor dinghy. I have a Mercury 3.3 2-stroke which is brilliant and light but I was hoping for a bit more grunt and to get the rib on the plane. I recently acquired an old Suzuki dt-4 which starts on the button and has the advantage of f-n-r gears and external tank if needed. It has recently been in my outboard motor place as it wasn’t watering and has had a good check over and is running nicely. However, when I put it on the boat it wasn’t as powerful as I was expecting and about the same speed as the Mercury. Should I be expecting more oomph? Am I missing something obvious?

I found even the DT6 was disappointing performance so upgraded to a T9.8 2 stroke which planes 2.7 inflatable at 18 kts.

 

[rotrax]

I have just upgraded my dinghy to a second hand 2.7m Waveline GRP rib replacing a seago 265 slatted floor dinghy. I have a Mercury 3.3 2-stroke which is brilliant and light but I was hoping for a bit more grunt and to get the rib on the plane. I recently acquired an old Suzuki dt-4 which starts on the button and has the advantage of f-n-r gears and external tank if needed. It has recently been in my outboard motor place as it wasn’t watering and has had a good check over and is running nicely. However, when I put it on the boat it wasn’t as powerful as I was expecting and about the same speed as the Mercury. Should I be expecting more oomph? Am I missing something obvious?

You can buy Suzuki's 5HP conversion throttle lever which allows a bit more butterfly opening. Or, you can do what I did and bend it a bit.

DONT allow the butterfly to go over centre!!!

It will stick on full throttle.

It is still not enough to plane reliably. You need a bigger donk for that.

 

[KompetentKrew]

Ideal outboard for a boat of this size is the two-stroke Tohatsu 9.8. Not cheap or easy to get ahold of, but you won't be disappointed.

 

[Chiara’s slave]

The trouble is, where do you stop? Getting the weight forward is easier with remote control and steering. We have that, and 25hp. Problem solved. Of course it’s all permanently rigged, and a lot heavier. You could do it with one of those outboard tiller extensions. If the boat is light, 10 hp will get you on the plane. Add a couple more people and it’s another thing.

 

[chris-s]

look for a Yamaha 8hp 2stroke, light and plenty of oomph!

 

[geem]

The trouble is, where do you stop? Getting the weight forward is easier with remote control and steering. We have that, and 25hp. Problem solved. Of course it’s all permanently rigged, and a lot heavier. You could do it with one of those outboard tiller extensions. If the boat is light, 10 hp will get you on the plane. Add a couple more people and it’s another thing.

You don't need to get forward if you fit a large planing plate to the outboard drive leg. You create loads of lift at the motor. We do this with a 15hp yam 2 stroke on a 3.8m grp tender. Both of us sit at he back of the boat. We previously had 9ft ribs with the same oversized planing plates. We never needed to sit forward. I have fitted a few plates to friends motors. It works really well

 

[Chiara’s slave]

You don't need to get forward if you fit a large planing plate to the outboard drive leg. You create loads of lift at the motor. We do this with a 15hp yam 2 stroke on a 3.8m grp tender. Both of us sit at he back of the boat. We previously had 9ft ribs with the same oversized planing plates. We never needed to sit forward. I have fitted a few plates to friends motors. It works really well

You are preaching to the converted. You still need enough horsepower though.

 

[M Cuff]

Thanks for the replies. It sounds like I’m expecting too much. The engine didn’t seem to reach full revs though but was better in a tank in neutral. The 3.3 is definitely lighter!