Water surface condition, fact or fiction?

[martyh]

I was told that a boat will go faster if the water is choppy compared to calm water. Was said the reason why is you get more air under the boat when the water is choppy.

The reason why I bring this up is, I had some work done to my 88 Reinell 173E Bowrider, OMC 4.3 with cobra outdrive, and I am not sure what the prop specs are.
Now it seems slower than the previous time I had it out. The power feels like it is down and the temp runs warmer than it did previously.

The first run, the water was a bit choppy and I buzzed the tach up to about 3200, we were just haulin, wasn’t even full throttle yet. Unfortunately, I don’t remember what the speedo said but it scared me a bit and I slowed it down. Needles to say I was very pleased with the performance, and the acceleration was just awesome.

I had a water leak issue and the repair job consisted of removing both the engine and outdrive assembly to reseal the transom, replaced cracked exhaust manifolds and flappers. (one was burned up) and the manifolds were in good shape.

The second run after the picking it up from the repair shop, it just felt slower. The water was calm and smooth and it just didn’t feel like it did before. I opened it up to full throttle this time and it went to 3500 rpm and stayed there and it read 36mph on the speedo. The temp bounces about 200, it comes down a bit at speed but climbs back up at idle. It seems a bit warm to me being raw water cooled with a 160 t-stat in it, and I had changed the O/D pump with the tuneup just before the first run.

I mentioned the boat being slower to the repair shop when I took it back to fix the water leak again, and he told me it was because of the water surface condition.

Is it a fact or fiction that the condition of the water surface makes that much difference in the speed of the boat? Any thoughts?

 

[b00tstrap]

Re: Water surface condition, fact or fiction?

Perhaps the mechanic meant it feels like you are going faster on choppy water vs. not?

200 deg. sounds a bit high in my opinion. My 88 merc 5.0L runs about 165.

 

[Gary H NC]

Re: Water surface condition, fact or fiction?

200 is to high for that engine. I would take it back to the mechanic before more damage is done.
I have the same engine-drive setup and it stays around 165 to 170..plus i'm turning 4200 to 4600 rpms at 45 mph..

 

[whywhyzed]

Re: Water surface condition, fact or fiction?

My 11 ft inflatable runs 24mph on flat water and 27 with a ripple.... but it's a flat bottom...you can feel the boat sticking to the water when it's butter-smooth.....
With a Vee hull, I doubt there's a benefit.

Regardless, flat or chop...3200 rpm will give identical speeds for your boat. (Unless the prop is wildly ventilating or something....)
There's no torque converter, the only slip is water on the prop and that won't vary more than .5% or so in different water with an i/o.

When my inflatable speeds up to 27, the engine revs higher...it's all direct drive.

 

[Daddy O]

Re: Water surface condition, fact or fiction?

Here's my 2 cents

My 1991 Rinker 181 4.3L Alfa One goes faster on smooth water than on choppy water.

 

[lilmandavis]

Re: Water surface condition, fact or fiction?

i cant wait to test mine out...little 16ft bass boat w/ merc140i6. should cook!

 

[Boatist]

Re: Water surface condition, fact or fiction?

Boats are faster on water with ripples or a small chop. When the people are going for speed records they wait for conditions with a ripple.

Now a big chop, 1 or 2 feet is not what they are looking for.