New Engine
 

Time to make the big decision... I've been reading and reading and reading about different outboards and have ended up between two brands, Etec (115hp or 150hp) or Yamaha (115hp). I have a couple questions.

Boat setup: '72 20' SF with 25" transom. I freedive/spearfish the channel island off Santa Barbara, CA. It's a ~30 mile crossing to get to the islands, it's rarely calm enough to reach speeds greater than 30mph. I'm more concerned with handling, safety and fuel efficiency than high speeds.

There is a ~30lb difference between the etec 115 and 150 will that be noticeable in handling/low planing speed? How about fuel consumption(ie. bigger engine works less for the same speed). I'm assuming there is a decent difference at high end speed.

What MPG can I expect at cruise from each motor(etec vs yamaha)?

When I look around the harbor everyone has Yamaha outboards which makes me think it will be easier to find a decent mechanic. I've always had two strokes and like that there is less maintenance and fewer moving parts.

In short what would you buy?

Let me know your thoughts.

Easy, 150 eTec. Search "Bushwacker", he has many posts on the performance of his 150 G1 eTec on his 20'er. I had a 4S 150 Yami on my 22' Pathfinder and it did a very nice job, however I like the 2S for the reasons you referenced (even though I just bought a 4S for my SeaCraft). True point on the mechanic issue, but Yamaha and their service $$$$$ are just crazy. Good luck.

I run a 2004 Evinrude 150 DI (pre-etec) on my 1968 19' with bracket and its the perfect engine. with lenco tabs, I can plane at under 15 mph and run 45mph on top. quick holeshot and 32mph cruise. 4mpg at cruise.

You are planning to cruise ~ 60 miles round-trip in "rarely calm" water. That's a tall order for a 20' boat by any standard! I would think that the ability to be on plane at low speed (15 mph or less) would be essential. From what I have read here it seems that even with a 90 ETEC you will top out in the upper 30's and cruise on plane as low as 12 mph if you have to. That's important when you are 20 miles from port and the wind starts to blow. I have not been on a 20 with that power but you could do a search on CSC for Terry England's "Marshtackie". He cruises long range with heavy loads with a 90 ETEC, I think he posted his numbers a while back.
If it were me I would choose the lightest motor I could get. Some of the 4-stroke 115's are pretty light; Mercury is 360# or so - not sure about Yamaha. I personally would be looking at the 90HP ETEC to do the kind of trips you are talking about but I understand that it would be below the "critical minimum HP" in the minds of most people. If I were planning to sell at some point in the future I would want to have a 115; more power is appealing to most buyers.
I would expect to cruise above 4mpg with any of the motors mentioned here.

Min plane speed of 12 is what you want.
I cant get below 16-18 w 365 lbs on a25 in transom
89 20 sf

Terry’s stats -
So Last Saturday two of us, 80#’s of ice in the fish cooler, 5 tanks, wet suits, dive weights and assorted sh!t. Ran 27 miles offshore to 38’ off of Bayport hunting for some Gag groupers before the season closes. Kinda’ raggity in the morning blowing out of the north 10 or 12, just starting to white cap.
Pushed the boat off the trailer at 7:30 and slid back on at 5:30. Never shut the engine off all day. Showed 71 miles on the plotter. Turned 3400 making 15 knots going out and 4000 making 24 knots coming home. Burned 14 gallons and a pint of oil (set for 50 to 1) An ’06 motor with about 700 hours on it.
Like Long Tall Sally, “she got everything what uncle Ter need”

I’d buy the 90 hp E-TEC which is MUCH lighter than either the V-4 or V-6 and should be enough power to do what you want! The SeaCraft VDH hull is surprisingly efficient and doesn’t need nearly as much power as the fat modern hulls designed for the heavy 4-strokes! You’re right, the V-6 is only about 30 lbs heavier than the V-4, which has the lowest hp/lb of any motor in BRP’s inventory since they added the V-6 lower unit. Terry England runs a 90 on his 19 and a pair of 115’s on his 25 Bertram, so I’d defer to his judgement, as I think he’s had good experience with both. The I-3 doesn’t have the 2-position exhaust valve of the V-4, which likes to run best at 4000+ rpm when the valve is in the high speed position! If you get into rough conditions and have to throttle down to 3000-3500 rpm at about 12 mph, I suspect the I-3 would be happier at those conditions if it’s propped right. The I-3 is probably about 100 hp vs 125 hp at the prop for the V-4. Terry can probably give you good advice on the prop. I’d lean toward a 4B prop, which will give you more stern lift and reduce min planing speed, which will be your single most important performance parameter for the type of running you’ll be doing.

Regarding fuel economy, the 4-stroke will be slightly better at cruise while the E-TEC will be MUCH better running at hull speed when it’s in the stratified charge mode (like 10 mpg!) so the overall difference in fuel burn will not be very large, especially if you spend a lot of time at low speed. The best data I can give you is from my S. Fl. Circumnavigation trip in my Seafari in 2010 with a very heavy cruising load, when I burned 158.5 gallons of gas and about 1.5 gal of oil to run 693 miles across the Okeechobee waterway, Lake O, down the gulf coast to Flamingo, across to Key Largo, and back up the east coast to Palm Beach for an average of 4.4 mpg. This was with a relatively inefficient PowerTec prop that only got about 3.7-3.8 mpg at cruise. I later found a BRP Cyclone prop that easily got over 4.0 mpg at cruise; your SF is at least a couple hundred pounds lighter so should do a bit better. And because they’re much weaker in low and mid-range torque as well as heavier, the 4-strokes may have trouble planing at 12 mph! This definitely seems to be the case on heavier twin engine rigs.

As far as maintenance is concerned, the E-TEC’s are basically very simple motors with some sophisticated but very reliable sensors and electronics and no valves to burn or adjust, so they don’t need much maintenance, plus you can buy the same basic software the dealer has that runs on a Windows laptop that will allow you to do a lot of troubleshooting. However in the 11 years and ~650 hours I owned my E-TEC, I never really had enough problems with it that I needed the software. If you check out www.etecownersgroup.com, you’ll find a very good forum, much like this one, that’s run by some very experienced E-TEC technicians who can answer any questions you might have on operation and maintenance!

Thanks for all the advise. Looks like I'll get a 200hp... just joking 90 Etec it is. I finally got all the wood out of my transom today, which means the tear out is complete and time to start rebuilding.

Good choice! Most folks today have never run the 20’ hull with only 300 lbs on the transom, but I ran my Seafari for over 30 years with a 1975 “115” that probably wasn’t much more than 105 hp at the prop, but it rode and handled great! Cruised at 20 kts with a heavy load in 2-3’ square waves all day long at 4500 rpm and 2.8 mpg, with WOT of 34-35 mph. Gas mileage with the E-TEC should be 40-50% better than that! The ride with the bracket and ~420 lbs of motor mounted 30” further aft was noticeably worse until I added some bandaids like an AV plate fin and 4B prop!

I’d still recommend using Costa in the transom and using a 4B prop and/or a fin on the AV plate for even better low speed performance. Good luck with your restoration!

Please post some performance numbers when you get squared away. I think that 90 is going to work just great. I remember when I first started getting into the Seacrafts seeing a couple of 20s with 90s on them and thinking "That thing must be super underpowered". Now that I have run my 18 with a 90 for the last 6 years and I've seen how little horsepower these hulls need, I can totally see running a 20 with a 90. More than enough power, rides great high and dry and gets good fuel economy. Long live Variable Deadrise !!!

Does anyone have specific prop recommendations for the Etec 90? I've seen 13-¾" x 15" props recommended on other threads? Brands? It sounds like people like 4B for the lift. I know props can take some trials to find the perfect one any help to get there faster would be appreciated.

The motor is on! I need to get a prop. The new 90s have the larger V6 lower unite and take 15" props. I've see people reference using 13x15. Would a 15x15 still work or will the larger diameter be too much with 15 pitch? Any advise or prop recommendation would be greatly appreciated. I'm hoping to go to a prop shop in the morning.

I could barely turn a 4B SS 15x15 PowerTec ELE4 to about 5400 with my 150 on the Seafari! Same with the 14.5 x 15 BRP Cyclone, so the 90 will never spin it fast enough! Ask Terry England what he runs on his 19!

That new motor sure looks good!! Good luck on the Seabass this season.

Thanks for the reply's. I'll post some numbers as I get this dialed in... and some seabass pics...

I took the boat out for a few minutes today. I just ran out a mile or so and ran back. The boat had 47 gals of fuel and minimal/no gear, just me. I used an aluminum 15.25" x 15 three blade prop (only prop I had access to that fits). I planned at 12-13 mph and cruised in the mid 20's with a fuel burn of 5.5mpg. Topped out a 35 mph at 5250 rpm. Like I said this was just a run out and back didn't mess around with anything just wanted to get the boat wet. The cavitation plate is exactly 1.5" above the hull line. I'll post more as I refine.

Thanks everyone for the help. I am amazed at how smooth the boat runs. couldn't be happier.

Holy cow those numbers look good!!!! It also looks great.

JBASS02, it would be nice to see how things are going with the new power. Have you gotten prop & everything dialed in? Looks like you made a great choice.

I've done close to a thousand miles on the engine already. The islands which we spearfish are 26 miles offshore so a typical day is around 80-100 miles. The engine is great! It gets ~4.5 mpg for the average day could be better but I typically run 48-5000 in the morning. At ~4000rpm(~23mph) it's getting 5mpg at ~5200 it get 4mpg(~35mph). Yesterday was our first day of big seas and the boat did great. We left the harbor at 5:20am to glassy seas and got to around the 20 mile mark before we decided to abort and dive coastal, we couldn't see over the waves which where beginning to break... I'm planning to redoing the deck and possibly building a half height cuddy this winter so I'll wait till then to dial in the prop and go stainless.

E-tec 90
 

The 90 E-tecs do fine. Lot’s of mid range torque with a very flat power curve. I don’t post much on the performance because I sound like another “Lying Fisherman”. I’ve worked mine like a dog since ‘06 on my “freighter”. I did have an EMM go out years ago, but that was covered under warranty. Other than that “touch the key and go”.

Good god and I though i racked up the miles. 1000 in two months, just wow.
checked my odometer 4225 in two years. It sounds like a perfect fit to you and the boat. Best of luck.
Ed & Sue

Finally had a smooth day and was able to get some accurate numbers. I was running solo with spearfishing/freediving gear and 50 gals of fuel so on the light side. The mi/gal numbers are rough... +/- .0001 :D not sure who set that as the default significant figure?

Hey T3, I'm not sure exactly what it was, but I think you forgot to load something!! I see some floor space available in the picture for some other stuff! :)

Yea, neither the MPH or GPH number are accurate to more than + 0.1 so any more than 1 decimal place is just looking at noise in the signal! What really counts at the end of the day is the overall average. My experience with the I-Command gage that provides instantaneous mpg is that the optimum speed for the 20’ hull is somewhere in the 22-25 mph range, which seems to be what your data shows and is about where it reaches minimum running angle.

The 1969 Boating Magazine test of the 20’ Seafari in the Literature section showed runnning angle decreased until speed reached 25 mph and then stayed constant until it reached ~ 35 mph. At that point it began to increase. I believe that’s because there is a slight wedge built into the aft 10’ or so of the outer panel, but that panel is completely out of the water at about 35 mph, which would eliminate the “trim tab” effect. If you lay a straight edge on the keel at the transom, it looks like there is a bit of rocker built into the inner panel, which would allow the bow to rise once most of the lift is coming from the center panel. That would allow the bow to rise and reduce wetted surface and increase top speed . . . Just one of many subtle but brilliant details that Moesly built into his designs that allowed his boats to dominate their classes in the Offshore Power Boat races!