New Engine Advice for 2001 20 Seacraft MA

[fishstu]

My 2001 Mercury 150 EFI ( 2-stroke) locked up yesterday - crankshaft bearings I think.

So - will probably will be re-powering - I think the 150 hp engine is a good balance of speed , fuel efficiency and weight for the Seacraft 20 hull. It was pretty quick - can't run at its top cursing speed in any sort of sea, gets up and go's with 5 on-board. I dont need a bigger engine than 150 hp.

BUT - I am open to:

The light weight Yamaha 115 4-stroke, the heavier Yamaha 150 4-stroke.
The lighter weight Mercury 115 4 stroke and Mercury 150 4-stroke.
Etec engines - the 150 probably.
Suzuki engines also would be considered.

Around here Yamahas are considered the most reliable, I see a lot of etecs and hear good thing about them - but hear from die hard Yamaha owners problems with etecs :-)

Reliability, ease of maintenance, engine life and fuel consumption are factors with reliability the main factor - I want to crank the engine up and go fishing.

I am in CT so service would be important.

Looking forward to hearing every body's options and experiences. ie performance of 115 hp, effect of heavier Yamaha 150, how the boat sits, water coming thru the scuppers etc.

Thanks

[Basketcase]

I hear the crowd here chant "Light is Right" on these hulls. I'm still a newb by comparison, but from what I've gathered here, these hulls are very efficient and dont like weight. For that reason, I've chosen the Merc 115 with Command Thrust. I've got a friend with a Yamaha 90 (older 2 stroke) on this hull and it does just fine. I have another friend with a Yamaha 150 4 stroke and it is quite stern heavy. IMO, too much weight for the boat. If one person stands in the rear, there is water coming in the scupper. With the research I've done, the Merc 115 is the lightest motor of that hp. You step up to 150 and that's not the case anymore.

[gofastsandman]

Originally Posted by Basketcase

I hear the crowd here chant "Light is Right" on these hulls. I'm still a newb by comparison, but from what I've gathered here, these hulls are very efficient and dont like weight. For that reason, I've chosen the Merc 115 with Command Thrust. I've got a friend with a Yamaha 90 (older 2 stroke) on this hull and it does just fine. I have another friend with a Yamaha 150 4 stroke and it is quite stern heavy. IMO, too much weight for the boat. If one person stands in the rear, there is water coming in the scupper. With the research I've done, the Merc 115 is the lightest motor of that hp. You step up to 150 and that's not the case anymore.

They run fine with an ole yami 70 2 s.
Light is right indeed.

[Fr. Frank]

Let me begin with the fact that I was manager of a SeaCraft dealer marina back in the early 80's. We rigged the 20" hulls with everything from a single 70 hp Evinrude, to a single 175 Evinrude, and all the Evinrudes and Mercury motors in between.

The most popular rigs for hp was either a 115hp V4 Evinrude, or a 115 Inline 6cyl Mercury. The next most popular were the 85hp V4 Evinrude, and the 90hp inline 6 Mercury. Only one time did I ever have someone come back because they didn't have enough hp, and that was a customer who was unhappy with the new 80hp inline 4 cylinder Mercury on the back of a 1969 20' Seafari, because he couldn't pull two skiers at once. He had repowered from a single 135 Mercury inline 6. So at his request, we added a second 80hp inline 4cyl Mercury, giving him twin 80 hp motors. He was happy with that.

I can think of no reason to power a 20' Seacraft with more than 140 hp except going faster than 40 mph and/or just wanting to spend extra money on fuel.

Even the boats I see rigged with 150 or 200 hp are running less than 20 mph offshore, and they have a lot more trouble keeping on plane at lower speeds because of the extra weight hanging on the back of the boat.

My '71 Seafari 20' with it's original Mercruiser 140 and trim tabs can hold plane at 12-13 mph offshore in 2-4' and still give me a fabulous ride, where 17-18 mph would have me airborne from time to time. I came in from 29-30 mile offshore Saturday in 2'-3', with the occasional 4' or 5', with a fairly short wave period, and I came in at on plane at about 13 mph all the way. Never airborne, never stuffed the bow. If I had too much weight on the back, I would have either had to fall off plane, or would have pounded the crap out of myself and my family.

The target weight is 300 lbs for a transom-mounted outboard. Get as close to that as you can.

[fishstu]

Fr. Frank
"I can think of no reason to power a 20' Seacraft with more than 140 hp except going faster than 40 mph and/or just wanting to spend extra money on fuel.

Even the boats I see rigged with 150 or 200 hp are running less than 20 mph offshore, and they have a lot more trouble keeping on plane at lower speeds because of the extra weight hanging on the back of the boat."


That's what the Yamaha dealer / installer says - he recommends the new lighter 115 Yamaha 4 stroke for that hull.
The dealer is a very good outboard mechanic and a good friend of my friend who runs a older version of the Yamaha 115 4 stroke on his Polar 20 and gets great gas consumption.
Maybe a new 115 is the way to go - I do have 5 people on the boat some time and take my daughter and her friends water skiing.

Would 115 hp handle that and what speed would a 115 hp manage ?

[Terry England]

Fishstu,
Bro'-in-law makes 36 mph with his 115 E-tec on a Seafari - Bimini up, loaded for camping.
I make 34 mph with on the stripped down Marshtackie Bowrider with the 10 year old 90 E-etc triple. 3600 rpm makes 20 mph, 5 on board with assorted "clutter".

[manitunc]

I have a 150 Evinrude DI on my 19' and it is a great balance of power and weight. Pops up on plane and accelerates hard. the 115 merc 4 stroke would be my other choice if you want to go a little lighter and less hp.

[gofastsandman]

Mid range is torque highly under rated.

[FishStretcher]

To thread jack a little.

With 4 strokes, one worries about burning exhaust valves at WOT if you run there for a long time. Is there a similar issue with an etec? Specifically running an etec 90 at WOT for extended periods. My 1999 Yamaha F100 is getting to the point where I am thinking about a replacement.

[Bushwacker]

Originally Posted by FishStretcher

. . . With 4 strokes, one worries about burning exhaust valves at WOT if you run there for a long time. Is there a similar issue with an etec? Specifically running an etec 90 at WOT for extended periods . . .

There are NO exhaust valves to burn on a 2-stroke E-TEC! And the harder you run 'em, the more oil they get, so the only limit on time at WOT is the thickness of your wallet! Terry England's 90 hp E-TEC seems to do a fine job pushing the 19' Marshtackie stern rider loaded down with 4 divers, tanks, all their dive gear, and a big cooler full of fish!

If you want to avoid burning exhaust valves, which is the weak link on any 4-stroke engine, the best thing to do is hook a vacuum gauge to the intake manifold just downstream of the carb or throttle body and observe a cruise limit of 5 "Hg. This is about 75% of max power and is the "Max Continuous Power" rating on the Lycoming/Continental piston engines used on light aircraft. These are premium heavy duty engines that have Stellite valve seats, positive valve rotators, and exhaust valves filled with liquid sodium for improved heat transfer and better cooling. (If I was considering a 4-stroke outboard, I would definitely ask if it had this sort of heavy duty parts in it!) Most of my engineering colleagues at Pratt & Whitney who ran inboards were well aware of this limit and did not run less then 5"Hg for very long. Many of them observed a limit of 7" and could get as much as 2000 hours before needing a valve job.

One friend, who was not an engineer, ran a vacuum gauge but didn't really understand the max continuous power concept, so he just set the throttle at 5" Hg, and whatever speed that produced is what he cruised at all the time! After about 300 hours, he not only had burned exhaust valves, the heads were cracked! And this was on a 302 Ford engine, which does not have the cylinder head hot spot due to adjacent center exhaust ports like the small block Chevy, so it typically has better exhaust valve life! This guy removed the I/O and converted his 21' Wellcraft Nova to a V-6 Merc outboard!