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Yeah 25mph is pretty cool I have to admit. I like the 20 mph with the ballast in even more. I was expecting a bit more though so the elation is mixed with light disappointment. I will find a way to output the nmea data to get real rpm.

I do wonder about the top speed not changing regardless of the weight. My old 50 would run at 8 mph with ballast and up around 16 without. It suggests that I have hit some kind of form-based barrier and I wonder if playing with the motor mount would have any effect.

With my 75 and a 13.75 x 15 I get a 2.5 kt dif from ballast to nil ballast

G

I should also add that loaded or not, I get the same speeds

Only ballast seems to change things

G

All depends on your life style.
I get 18mph on my new Bigfoot 50 and is heavy loaded.
I cruise at 7-8mph @ a average of 6-8 mpg.
If I went 15mph, I would get 2.4 mpg.
So burn up the gas or maybe sail.
A 100 hp engine will get you to 25or 30 mph but you get only 1.4- 1.8 mpg.
I guess is you buy at local gas station or fuel up at Marina.
Regardles, your just burning fuel.
I stiil think, it's not how far you go, It's enjoying your time getting their.
Dave

dlandersson wrote:25 mph is 10 mph more than I get.

DaveB wrote:I stiil think, it's not how far you go, It's enjoying your time getting their.

Personally I agree with you. I would way rather sail than motor, but with three young boys on board it's more about BEING there than GETTING there. They have a patience limit of about 45 minutes before things start degenerating and I don't like just popping a movie in to keep them quiet. For them, a trip on the boat is a fun and excellent way to get somewhere interesting, but being cooped up in a small space for extended periods is tough for them. A 4 year old just doesn't have the same perspective on sailing as I do.

45 minutes gives me a range of about 4 miles downwind or crosswind under sail. With the 90HP it gives me a range of 15 miles in any direction with full ballast for safety. WIth a stop to stretch legs or swim or snack, any interesting destination within 30 miles is easily do-able in a day-trip.

I suspect that as they get older their tolerance level will increase, and thus our range, but also that their interest in motor-based activities such as wakeboarding will also increase. The ability to motor-sport a bit was a partial factor in the decision to get the 90.

Starscream wrote:

DaveB wrote:I stiil think, it's not how far you go, It's enjoying your time getting their.

Personally I agree with you. I would way rather sail than motor, but with three young boys on board it's more about BEING there than GETTING there. They have a patience limit of about 45 minutes before things start degenerating and I don't like just popping a movie in to keep them quiet. For them, a trip on the boat is a fun and excellent way to get somewhere interesting, but being cooped up in a small space for extended periods is tough for them. A 4 year old just doesn't have the same perspective on sailing as I do.

45 minutes gives me a range of about 4 miles downwind or crosswind under sail. With the 90HP it gives me a range of 15 miles in any direction with full ballast for safety. WIth a stop to stretch legs or swim or snack, any interesting destination within 30 miles is easily do-able in a day-trip.

I suspect that as they get older their tolerance level will increase, and thus our range, but also that their interest in motor-based activities such as wakeboarding will also increase. The ability to motor-sport a bit was a partial factor in the decision to get the 90.

I hear you
I have 2 girls
currently 13 15

Sailing is for Dad
Powering is for them and their friends

I hope that some day they will want to learn how to sail and maybe even enjoy it

Who knows

G

Ditto - two kids, 6 & 8

Starscream wrote:

DaveB wrote:I stiil think, it's not how far you go, It's enjoying your time getting their.

Personally I agree with you. I would way rather sail than motor, but with three young boys on board it's more about BEING there than GETTING there. They have a patience limit of about 45 minutes before things start degenerating and I don't like just popping a movie in to keep them quiet. For them, a trip on the boat is a fun and excellent way to get somewhere interesting, but being cooped up in a small space for extended periods is tough for them. A 4 year old just doesn't have the same perspective on sailing as I do.

45 minutes gives me a range of about 4 miles downwind or crosswind under sail. With the 90HP it gives me a range of 15 miles in any direction with full ballast for safety. WIth a stop to stretch legs or swim or snack, any interesting destination within 30 miles is easily do-able in a day-trip.

I suspect that as they get older their tolerance level will increase, and thus our range, but also that their interest in motor-based activities such as wakeboarding will also increase. The ability to motor-sport a bit was a partial factor in the decision to get the 90.

Finally had an issue with the Suzuki 90. Started running rough. There was some water in the low pressure fuel filter. Drained that started running ok then rough again. Drained the fuel vapor separator. No water. Still not right.

Dropped of at our dealer today. 2.5-3 weeks wait. Under warranty. Good for me, I have parts to finish.

I forgot what a 50 is like. Full ballast maxing out at 12.5 MPH, just like our Honda 50. Very frustrating trying to outrun a potential storm last weekend. If the engine was running ok it would let us sail late (low winds) then throw down the throttle to get to our destination 25 miles away. We have more sailing time with a bigger motor when trying to make a destination.

Erik (Knot Shore/Suzuki 90) made a doughnut around us to show off his alpha male status over our wounded boat

Victor

Only 3 weeks - you must know someone. Mine took about 5 weeks and I did not have a spare motor

Victor,

Are you running a 50 while your 90 is in the shop or were you comparing you wounded 90 to your old 50?

vkmaynard wrote:
I forgot what a 50 is like. Full ballast maxing out at 12.5 MPH, just like our Honda 50.

Victor while I sympathize with your motor problems, that comment actually makes me feel a little better about my Etec purchase. Your boat with a Honda 50 could do 12.5MPH with ballast while my boat could only do 8.5 MPH with the same motor. If I remember your previous posts and videos correctly you topped out at over 30mph with the Suzuki DF90, while I top out at 25 with the Etec90. I was wondering if I had a 70HP in disguise but maybe the physical characteristics of our boats are different? Could bumpy bottom paint and/or the motor position on the transom have anything to do with that?

Starscream wrote:Yeah 25mph is pretty cool I have to admit. I like the 20 mph with the ballast in even more. I was expecting a bit more though so the elation is mixed with light disappointment. I will find a way to output the nmea data to get real rpm.

Your engine is rated 90 hp at 5000 rpm, with a target engine speed range of 5000-5500 rpm. Since rated hp is being achieved at the prop shaft, which is what OB power rating is taken, I have to think that you've achieved the best it will do, as far as boat speed goes. Assuming the tachometer is accurate.

Some small improvement may be achieved with a different prop, but that would be through an increase in efficiency, and smaller and faster is generally less efficient than larger and slower.

I'd be inclined to try to get the engine speed up closer to the 5500 rpm max, since that's in the lightest, cleanest configuration you can manage, but I don't think you'll get much or even any more speed out of it unless you can make it more slippery.

As to the ventilation plate*, if it's just touching the water behind the boat (because it's set even with the bottom of the hull), you probably can't improve on that by changing engine height. Lower will put more of the lower unit in the water, which adds drag.

I wish mine went that fast.

*Ventilation is when the prop is sucking air from the surface - it's what the ventilation plate is there to prevent. Cavitation is when the prop or even some part of the lower unit causes a drop in pressure below the vapor pressure of the water and it 'boils'. The collapsing bubbles are tiny but violent, and erode the prop over time.

So my only solution is: http://www.sciencedirect.com/science/ar ... 4003002881

In my early postings here I once posted an article that I saw in a British Yachting magazine on a product called HiSpeedKote (http://www.hyspeedkotecanada.com/) but if I remember correctly the suggestion wasn't well received. It's a good marketing job though and if the product was actually available in Canada I would sure be tempted to drop $80 to test their claims. Anyone in the US willing to give it a try?

Starscream wrote: Could bumpy bottom paint and/or the motor position on the transom have anything to do with that?

Our boat has no bottom paint. I scrapped it off when we got our boat the sanded with 320 because I read that little bit of roughing helps with speed (flow tripping) (oops should not disclose). Is that why we are so fast?

Victor

Starscream wrote:Yeah 25mph is pretty cool I have to admit. I like the 20 mph with the ballast in even more. I was expecting a bit more though so the elation is mixed with light disappointment. I will find a way to output the nmea data to get real rpm.

I do wonder about the top speed not changing regardless of the weight. My old 50 would run at 8 mph with ballast and up around 16 without. It suggests that I have hit some kind of form-based barrier and I wonder if playing with the motor mount would have any effect.

The difference between 8.5 knots and 12.5 knots in these boats is a very small amount of power, less so than at any other point on the power curve for these boats. At 8.5 knots the boat is generating as large of a bow-wave as it will make, and is trying to "power" over that bow wave. Once it gets over the top, the power difference between 9 knots and 12 is almost flat, so the boat goes straight to 12 knots and then begins climbing the curve again.

So your 50 was just barely under the amount of power needed, and with just a little less weight it would have made it to the expected 12 knots.

Of course, all of that is moot now with the 90

Matt