repower for 1977 20' CC

tjhilsabeck · #1 09-18-2013, 09:51 AM

I've been nursing along my 1984 Mercury 200hp for years now and I'm ready to stop worrying about it and choking my family with smoke. Unfortunately, I'm kind of spoiled with this 375 lbs. motor that pushes my boat along at 45 mph on flat water. I want to go with a 4 stroke so I can take it up to Lake Tahoe in the summers. I'm considering either the Yamaha or Mercury 115hp. Does anybody out there have this setup? If so, can I get a cruising (3500rpm) speed and top end speed?

DonV · #2 09-18-2013, 03:27 PM

Wait....don't tell me!!! CA does not allow etec two stroke engines in Lake Tahoe?

Bushwacker · #3 09-18-2013, 08:30 PM

E-TEC's meet the emissions requirements for Lake Tahoe. They even mention that in one of their ads. You might check out the 115 E-TEC - it's the same weight as your current motor and is actually about 120-125 hp at the prop, with a LOT more mid-range torque than the 4 strokes! Should push that boat to about 40 mph.

Normagain · #4 09-18-2013, 09:48 PM

I have an 06 Yamaha F115. Here are some numbers with a Solas Amita three blade aluminum 15 pitch prop with 40 gallons of fuel, 45 gallons of water and just me. When fairly lightly loaded it has good power and great economy, was averaging about 4.5mpg. I have a large fuel tank and when I had 1 passenger, 60 gallons of fuel, 45 gallons of water and 80lbs of ice last weekend out of Mission Bay, I was lucky to see 3.4mpg and the boat was pretty sluggish. I still was able to make 20mph at maybe 4500rpms.

I would go Suzuki DF140 if your going new. I was lucky enough to find the F115 used earlier this year or that is what I was getting. I do wish I had the power for those long San Diego runs, but mainly for fuel economy!

rpm mph
700 2.7
1000 4.1mph
1500 5.3
2000 6.7
2500 7.9
3000 9.2
3500 14
4000 20
4500 26
5000 30
5800 35

Normagain · #5 09-18-2013, 09:59 PM

Also, I also built my transom to 25", built the rear end light, and moved the batteries in the console. My batteries are AGM and weigh 150lbs together. If you fish the salt much, would definitely move the battery(s) with the heavy motor and a 20" transom. You are at 375 now, so the battery move would compensate nicely and give you similar weight in the back.

fly4navy · #6 09-19-2013, 10:23 AM

My 1974 CC 20 looks exactly like yours with the same type of T-top. I repowered this spring with a new 115 E-TEC having removed the old 98 Mercury 115
I am extremely happy with the move. I tend not to max it out but have taken it to 34 mph at 5000 rpm. I am most efficient at 4300 rpm doing about 25 kts. running at 4.5 mpg.. Oil comsumption is extremely low.
Engine has been 100% reliable with not so much as a hiccup. It is smooth and very quiet. Can't say enough good things about it. On top of that...its sexy looking.
I would find it hard to put together a better weight/ performance combination for the 20 CC Seacraft.
My only sqwak is that...mounted on the 20 inch transom, my lower unit kisses the water for about 1 inch. Not my preference in salt water.

mrobertson · #7 09-19-2013, 01:58 PM

I have one of the late 80's Tracker Seacrafts and in those years the boat was rated for a 225 and had a 25" transom. Given those ratings, one would never think a 115 would be adequate or even acceptable.

Where i fish on the chesapeake bay, it's always choppy. A tight 2-3 bay chop can make it miserable in some boats.

I am running a yamaha 115 2 stroke with a stern lifting prop. With the light weight on the stern, i can hold plane at probably 14 - 15 mph (no tabs, no hydrofoil) with any load i have ever had on board. Makes it very nice when it's rough.

I cruise @ 27 mph 4200 RPM's. WOT gets me about 34 mph @ 5500 RPM's.

Everyone has their own opinion of rough. If it were me, and you live/fish where its rough most of the time i would be looking at 2 stroke engines in the 115 - 135 HP range and build it around low planing speeds. The hull needs to get up out of the water to be efficient. Hard to believe but i have passed by similar sized, and even bigger boats where the captain was working the throttle. I trim the engine all the way down and let her run along at 15 mph, the landing is soft and im not touching the throttle.

McGillicuddy · #8 09-19-2013, 05:00 PM

Welcome aboard tj, good to see another SD SeaCraft.

I would look at the Etec 115 or the Suzuki 140. Optimax 115 is same weight 375/390 as Etec and cheaper, albeit louder, but the etec has more cojones

. The zuke is about 420 lb with oil.

Between J&M MotorSports, and Pacific Marine Supply, there is enough support for the zuke service, and its gearing will offer much better performance than the 400 lb. 4-S Merc or Yamaha 115s .

Plenty of Merc service options, but not sure who's working on Etecs other than Sunset Marine, in El Cajon. Etec and Optimax, can both be used at Diamond Valley, Tahoe or wherever.

Bushwacker · #9 09-19-2013, 11:10 PM

Quote:

Originally Posted by mrobertson

I have one of the late 80's Tracker Seacrafts and in those years the boat was rated for a 225 and had a 25" transom. Given those ratings, one would never think a 115 would be adequate or even acceptable.

Where i fish on the chesapeake bay, it's always choppy. A tight 2-3 bay chop can make it miserable in some boats.

I am running a yamaha 115 2 stroke with a stern lifting prop. With the light weight on the stern, i can hold plane at probably 14 - 15 mph (no tabs, no hydrofoil) with any load i have ever had on board. Makes it very nice when it's rough.

I cruise @ 27 mph 4200 RPM's. WOT gets me about 34 mph @ 5500 RPM's.

Everyone has their own opinion of rough. If it were me, and you live/fish where its rough most of the time i would be looking at 2 stroke engines in the 115 - 135 HP range and build it around low planing speeds. The hull needs to get up out of the water to be efficient. Hard to believe but i have passed by similar sized, and even bigger boats where the captain was working the throttle. I trim the engine all the way down and let her run along at 15 mph, the landing is soft and im not touching the throttle.

Carl Moesly designed the 19/20' hulls in the mid 60's for the biggest outboards available at the time, the I-6 Merc and the V-4 OMC's, which were right around 100-110 hp and less than 300 lbs. It's a very efficient hull that rides best with the light motors it was designed for. Ran mine for over 30 years with a 1975 115 Evinrude that gave me about the same performance you're getting. It would plane at 12 mph with trim tabs and allow you to run thru 2' square waves common on the Bahama Bank very comfortably, SITTING DOWN! Averaged about 2.8 mpg on 6 trips to the Abaco's running with very heavy loads, including 65-80 gallons of gas, 35 of which was even in the main tank!

Modern 20' boats with 8' beams and heavy 4-stroke motors seem like they won't plane below about 20 mph, and they're evidently so inefficient that most folks today seem to think that any 20' boat that doesn't have at least 200 hp is seriously underpowered! All I can say is that it appears that modern boats still haven't caught up to where Moesly was over 50 years ago!

McGillicuddy · #10 09-20-2013, 12:30 PM

The other motor I might consider would be the Suzuki 90. Bitsamonkey showed some very impressive numbers on his 18. If i recall correctly he was showing 37 mph top end and cruising a 27 getting 6.5 mpg or so. Obviously these 4 cyl. motors are no speed match for the 2.4 L Merc, but the bennies out weigh that for me all day long. There are still some of these around with originally rigged evinrude 75 and 85 hp motors.