Question on power
 

Hi. I have 1970 20 ft cc Seacraft.Always ran 115 Johnson cross flow which is fairly light.320 lbs or so. Now I'm looking to repower without adding 80 plus lbs. Any opinions on a 90 hp Yamaha 4 stroke being able to push her?Thanks

Lackler, I just purchased a 1989 20' with a f115 on it. It will run abut 40 at full throttle. That's still a little slow for me. I'm considering up grading to a f150 once I determine if it's safe to put a 500lb motor on the boat. I see other people running them but want to preserve the transom as much as possible. It's never been rebuilt and I don't wish to have any problems with it. I'm in Baton Rouge if your looking to pick up a f115 with 460 hours on it.

I know guys run the new 90 etech and love them on the 20s. Search for posts started by fly4navy. He has one and I think he has posted some numbers. Etech is a two stroke so it will def be lighter than the yami 4 stroke. Prob better economy and everything else than the yami and I have a 115 yamaha.

An F150 is not an "upgrade" on your Seacraft 20 hull.

I have a 2000 carburated Yamaha F100. Basically the same outboard- a little higher redline. I am happy with it. I run a Solas Amita 4 15" pitch prop. It is 4 blades and aluminum. And it stern lifts nicely.

Dragging a below surface foil and a kicker, I can hit 34 MPH. If I dropped the foil and kicker, I bet I could pick up a few MPH. But the "hydro shield" foil/wing that runs below the prop makes for very nice planing speed and helps lift the 58 lb kicker and main engine out of the water nicely. Hole shot is very good with this prop on this boat.

Without a kicker, I bet that prop or maybe the 17" pitch version would let you run something like 37 MPH and maybe plane down to 13 MPH without tabs. I think there is more in it with a better prop (stainless, more tuning) but a $120 prop should get you this far. I think the hole shot on the 15" is much better, though. I have both and keep the 17" pitch as my spare.

I put batteries under the console, and dropped the fuel tank size to 20 gallons and put it under the console. That helps balance. The great MPG of the Yamaha means that 20 gallons is a lot of range: ~100 miles. And a 5-6 gallon Jerry can on the deck can be a reserve tank.

Then I filled the old fuel tank compartment with foam and under the cap to help make it nearly unsinkable.

The engine itself is quiet and very corrosion resistant. The older carburated ones have small jets and don't like dirty fuel with ethanol in it. You just have to be good with filter changes and draining fuel bowls when you store it. EFI would be nice.

Why would you say its not an upgrade, thats a nice motor?

Indeed the Yamaha F150 is a fine motor. I simply believe overall performance of the 20 hull will suffer with a 480+lb motor back there.

I'm sure others would suggest otherwise. Just my opinion.

Original poster asked if a 90 hp Yammie 4-S would push his 20. I think it would be fine.

Second poster brought up the 150 idea which I tried to inhibit based on the very weight he expressed concern about. Granted in my response I failed to express why I felt that way.:o

my 200 merc is 415 - can't imagine much more working very well

I went through the same process about a year ago as I had an almost new 90 E-TEC and considered installing it on my 74 20 ft. CC (20 inch transom). I never did that however and went with a new 115 E-TEC and sold the 90 with my old boat So....I am just not sure what the performance woulf have been with the 90...but can tell you that the weight of the 115 E-TEC (at about 380 lbs.) is just fine and leaves my scuppers dry in just about all stages.

Thanks for the info.It still concerns me toting around extra weight.I have seen another 20 in my area with a 135 etec and it really looks like it squats.

It probably does squat a little. The 25" shafts are about 390 lbs. The hull was designed with a 300 lb motor in mind. Moving batteries forward and countering the weight some may all you need. And a good vortex scupper insert of course:cool:.

I'd love to get some performance numbers on an e-tec 90. I'm guessing they'd be very close to my 115 Merc inline 6 with exceptional economy.

E-tec 90 / 19' Moesly SeaCraft
 

I have an E-tec 90 on a 19' SeaCraft. Yes a 19'. it is an old bowrider that I stripped down years ago to haul freight out to Cayo Costa in Boca Grande.
Remember, when they first built these boats the BIG motor was a Mark 78, 75 HP "tower of power" Merc. Everybody said I needed a 200, but I stuck by my guns. My 19 with the 90 E-tec turning stock Evinrude 3 bladed aluminum props goes as such:
13-3/4 x 15" 3200 RPM - 18 Knots cruise, WOT (4800) 33 Knots 3.8 MPG
13-3/4 x 13" 4200 RPM - 18 knots cruise, WOT (5800) 27 Knots 4.5 MPG
The boat is very light, but this data is with three divers, 7 tanks, two coolers and 70# of ice, plus dive gear. The marina that begrudgingly installed the motor after they took a Johnson V-4 VRO 120 off were shocked at how well the boat ran.
I just ordered a 14" SS pitch (X13-1/4" dia) from Ken at PropGods in Sarasota because the 15" was not letting me turn up full RPM and the 13" had me spooled up to the rev-limiter. There is a picture of the boat on the Moesly web-site under "Proud Owners - 19's". It's the last one on the page.
The secret is that the 90 E-tec is rated at 5,000 rpm and all other E-tecs are rated at 5500 - at 5500 rpm the little 78 cubic inch, harmonically balanced triple make 101 HP! The down side is that they are super-sensitive to water of crud in the fuel. The VRO's were like garbage disposals as long as you disconnected he oil pump!

Terry, Thanks for the feedback. What prop models were you running before, and what model are you going to.

They were standard issue, John-Rude three bladed props. I went out in the garage and looked at the boxes they came in and they don't refer to them as anything special. After consulitng with Ken he said the 15" seemed to have "negative slip" numbers, whatever the heck that is. He said the 13" nembers looked right, but agreed I was "spooled up" too much at 5800 WOT. He suggested a Powertech S.S. NRS3 13-1/4 X 14. Along with the difference in cruising speed I noticed a big differennce in my ability to lift the bow. The old Moesly Bowriders had a little bigger forefoot or something because the boat will carry a ton of weight in the front and still ride "bow high", No matter what I put in the front it will not ever "plow". With the dang 15" I could have another 1' of lift if I need it when thiings got really sloppy.
I run a lot up at Bayport (Weeki Wachee) and all the channels look like the one coming out of Pineland Marina down on Pine Island. That place will destroy skegs, fold up props and occationally shear off lower units with the limestone bottom. I run aluminum up there because I'd rather repair and aluminum prop than replace a driveshaft!
McGillicuddy, I will let you know how things run with this new wheel from Ken as soon as I get a chance to try it. It looks like the last weekend of Gag Season will be raggity, so I'm liable to just leave it on the trailer until it eases up some. I've been beat up for so many years trying to go when it was snotty out. Now I just don't think there is any sense in spilling your wine, just because you have a SeaCraft.

Roger that, don't spill the wine, rather, dig the girl...I be waiting to hear the results. It's an interesting choice to me. Seems like you'd want to get the stern up in the skinny waters. That prop is considered hard to turn with its "extensive cup and 25 deg rake" so I wonder what the thought process is. I guess it will allow you to run the motor higher. Look forward to hearing more. Seems it will make the bow run high.

That 130 range has recently changed - the 115 and 130 were both V4 motors - the 130 or maybe 135 now was recently changed to a V6. If its a V6 that is probably why, as the 400lb's like I have doesn't really squat and scuppers work pretty well - mine is an MA and that may make a difference - there are water pics of my boat in the last west central meeting.

"Now I just don't think there is any sense in spilling your wine, just because you have a SeaCraft"

Amen brother!! Three years ago, on the last day of a guys weekend fishing trip, we went out in the 'ol 23' Seacraft into what the NOAA/NWS folks said it would be "5' to 7' seas, and It was more like 7' to 9' and it was so bad I was hoping and praying no more fish would hit the lures. That was it....in my case, never again, no more spilling the beer!!!!