Small atlantic 21 and sr5.4m rebuild

[diesel do]

Originally Posted by gotchiguy

It's a Honda...what do you expect!

I think this is on topic. Apologies if it is considered not to be.

You here it said occasionally that the big Honda engines are gutless.

Does anyone have any real word back to back experience between Honda and other brand engines of the same size on the same boat?

Physics says that ultimately horsepower dictates terminal speed if all other factors remain unchanged. Torque is responsible for how fast you get to that top speed, ie acceleration.

If propped to take advantage of the horsepower, terminal velocity for the same boat comparing two engines with the same hp from different brands should be identical. I'm talking about two engines that weigh the same, ie the current crop of four stroke Merc/Yam/Sukuki/Honda.

My question is , does this work out in reality?

[benjytaylor]

[benjytaylor]

Here is the solas prop on my Honda 225

[benjytaylor]

I'm guessing it is a 27P

[Boats&Outboards]

What was it revving out at ?

Peter @ Boatsandoutboards4sale ~ www.BoatsandOutboards4Sale.co.uk ~ 07930 421007

[benjytaylor]

Originally Posted by Boats&Outboards

What was it revving out at ?

Peter @ Boatsandoutboards4sale ~ www.BoatsandOutboards4Sale.co.uk ~ 07930 421007

Don't judge Peter but I didn't have the rev guage attached. I was like a kid in a sweet shop and needed it on the water. Just could here the engine hardly working hard at all

Funny enough I had the same issue when I had the 2x 75's on it. I put SS 19P on them and the speed reduced to 33knys and the engines would only rev to 4300rpm. Put the 15's ally props back on and got 36knts and 5500rpm. Better pickup too. So I think I'll drop to 15/16P SS mirage or laser11

[benjytaylor]

Oh and fit the rev guage too ;-)

[Boats&Outboards]

Fit the rev counter first

Peter @ Boatsandoutboards4sale ~ www.BoatsandOutboards4Sale.co.uk ~ 07930 421007

[benjytaylor]

Originally Posted by Boats&Outboards

Fit the rev counter first

Peter @ Boatsandoutboards4sale ~ www.BoatsandOutboards4Sale.co.uk ~ 07930 421007

I won't be buying a prop before I do that don't worry ;-)

[Chris]

Originally Posted by benjytaylor

I'm guessing it is a 27P

A couple of things. That Solas Prop will probably be to higher pitch I would think you would need a 20 or 22" prop. Mine is a 15" Diameter by 19" So whilst the solas you have is probably the right diameter I think it is going to be far to higher pitch.

I have a Mirage 19" and get about 46 knots on a 7 meter Vipermax which is quite a heavy boat.

If you overprop a Honda there are two issues....

At about about 4000RPM the IAB butterfly valve opens allowing the engine to take in more air through the manifold at the back then at 4,500 RPM the V-tec kicks in allowing the engine to switch cams and this gives a big power boost and you can hear the engine note change.

So if you are not pulling at least 5500 RPM at WOT (I pull 5800 at WOT trimmed out) then you will be seriously down on performance.

The second thing is that looking at your pics the engine sits low when at rest. This is not a huge problem in itself however you must be careful when starting the engine as it can suck up water into the bottom cylinders through the exhaust thw issue is highlighted in the Honda Service Bulletin #56.....There is lots of info about this here.

Exhaust manifold modification BF 225 and BF 200

If you engine is post 2006 this should not be such a problem BTW...

Finally one thing to check is the IAB vale at the back of the engine at the bottom. This can sieze up if the engine sits low in the water. I have put a thread about this here....

225 IAB Valve

Good Luck !!!

[gotchiguy]

Originally Posted by diesel do

Does anyone have any real word back to back experience between Honda and other brand engines of the same size on the same boat?

Yeah, Honda BF50 & Suzuki DF50 on a zodiac pro basically no difference

Originally Posted by diesel do

Physics says that ultimately horsepower dictates terminal speed if all other factors remain unchanged. Torque is responsible for how fast you get to that top speed, ie acceleration.

Yes I think that is true. Why is why 2/ have better holeshot because in general they have more torque.

Originally Posted by diesel do

If propped to take advantage of the horsepower, terminal velocity for the same boat comparing two engines with the same hp from different brands should be identical. I'm talking about two engines that weigh the same, ie the current crop of four stroke Merc/Yam/Sukuki/Honda.

But half of the point is that they don't weigh the same! The Yamaha, Suzuki and Honda weigh ~265kg while the Mercury Verado is 290+kg. Propping to the correct RPMs is hard, prop slip etc etc They don't end up going the same speed ever. And that's before you compare them to the lighter 2/s like Optimax and Etec down at 220kg for this hp. kW ratings available here: Engine Certification Data | Heavy Trucks, Buses, and Engines | US EPA bit of a hassle to find the exact engine though

[benjytaylor]

This should make the difference 27P before. 19P now :-)

[benjytaylor]

45.1knts and well planted!! Great pickup with the 19P prop and the engine sounds happy :-)

[benjytaylor]

Updates will continue :-)