rebuilding/repowering a 20' center console
 

New to this forum, I've got a 1969 20' center console that I'm in the middle of a restore and can't decide what to do for powering. I've had Don Herman build a twin bracket and am considering a twin engine installation. My thought was to find leftover a pair of yamaha 90 2 strokes, anyone ever heard of a 20' with twin's. 2nd option is a single 200hpdi or a 250 four stroke. The deck level has been raised alot so, water coming in is not an issue. Don says the twin bracket will offset about 800lbs in buoyancy, so just sitting shouldn't be a problem. I'm worried once the boat gets up on plane with alot of weight what will have to be done with trim tabs to counter, Any suggestions are greatly appreciated.
Thanks,
John Carpenter

Re: rebuilding/repowering a 20' center console
 

HI JCARP, welcome to the gang. I had a '75 20MA with twin 70 hp Johnsons mounted on the transom. No issues with the twins but when I repowered with a single 175 I was much happier. I'm not a big fan of twins and if it were me, a 150-175 2 stroke would be my choice. A 250 4 stroke on a 20 is overkill IMHO whether the bracket can offset that much weight or not.

Re: rebuilding/repowering a 20' center console
 

Welcome to the forum John. You've asked some good questions, and there's lots of good info to be found from very knowledgeable folks here!

When it comes to powering a 20, especially with a bracket, lighter is better (for better ride and handling, and a low min-planing speed). That leads you towards a 2 stroke. If you want the smooth running and low fuel burn of a 4-stroke, a DI 2-stroke will do that, although the E-Tec's seem to be the only one that also match the low noise level.

As far as twins go, personally I look at them as more cost and fuel burn, with twice the maintenance, and twice as much to go wrong! And if you if you don't go big enough to be able to plane on one engine, you might as well go with a bigger single and a small kicker! And, as the military would say, if one of the twins quits, you still won't be able to "complete the mission" any better than if you had a big single and a small kicker! A single 130 or 150 would be cheaper, quieter, handle better, and burn less gas. A 90 hp 2-stroke would probably plane a 20 if the other one died, IF you carry a spare low pitch prop. (Maybe a plastic Comprop where you could buy a single hub and 2 sets of blades for right and left hand rotation!) As for reliability, you might be better off with a modern well maintained single than a pair of older twins that might not get the same level of maintenance.

I've made a number of posts on the subject of brackets and motor weight, so just click on my username and you can review all my posts for more info. Denny

Re: rebuilding/repowering a 20' center console
 

Thanks for the input. My reasoning for thinking about twins was that I'm going to use the boat as a tender over in the bahamas and wanted to be able to get back. If the boat will plane on a single 90 that's a bonus. Not a big fan of a kicker engine because I find I get lazy and don't run it as much as needed and then when I need the kicker it won't run. I'd appreciate if anyone has performance stat's on a bracketed 150hp thru 200. The smaller I can go and still get great performance the better. I don't really care about 2 stroke versus 4 stroke, the noise of a 2 stroke and the oil tank isn't a issue. I had a 200hpdi on a wellcraft v-20 steplift before this boat and that would hit just 50mph with only myself in the boat.
thanks again,
John

Re: rebuilding/repowering a 20' center console
 

A 175 would be my choice if I could pick one. The 140 works well and sips gas but I'd like more power to plane easier when i'm fishing with a heavy load. Topping out at 40mph is ok, but i wouldnt mind hitting 50.

175 Zuke or 175 Etec would be my choices.

Good Luck and post us some pics!
SOS

Re: rebuilding/repowering a 20' center console
 

Thanks, will post some pics this weekend.

Re: rebuilding/repowering a 20' center console
 

One other thought, Don Herman said If I put a single on I need 30" shaft and twins 25" shaft. In just looking if I drop below 200hp it doesn't seem any of the engines are offered with 30" shaft, any thoughts?

Re: rebuilding/repowering a 20' center console
 

5" extensions kits are readily available for just about any motor 75hp and above except most 75-115 hp 4-stroke Yammies and all Suzuki . But I understand the Yammie shafts extensions will be available later this year.
Go to Bay Manufacturing

I know of nothing available for any Suzuki.

Re: rebuilding/repowering a 20' center console
 

I would double check that with Don. Those numbers apply on a 23' but not so sure on a 20'

Maybe Bushwacker (HermCo bracket, Etec 150) will chime in again. I think Denny's Etec has 25" shaft...

Re: rebuilding/repowering a 20' center console
 

I had double checked with Don before I bought the bracket, he had made this one special as the width was less than the one for the 23'.

As for the engine extension kits, I didn't know they were available, will check into that. I'm leaning toward yamaha anyway as I've had good luck with the 3 yamaha's I've had before.
Thanks,
John

Re: rebuilding/repowering a 20' center console
 

John, if you'll PM me with an E-mail address, I can send you some Excel spreadsheets/plots from a bunch of prop testing with data from I-Command system on fuel flow/gps speed/rpm and prop slip calculated. Also have a spreadsheet comparing specs/materials, etc. on all the 140-175 hp motors that I put together when I was trying to decide on a motor. My motor is a 25" shaft. Don't know if the 30" shaft is available on the small V-6 but you should be able to find out from this link.

A bracket is typically worth about 3 mph in top speed. I've seen 49.5 mph on gps on my boat with a full tank of fuel and just me on board with a 4B 14x21" pitch prop. Could probably get more with the right 3 blade prop, but they don't have enough stern lift for my stern heavy rig. Also think the motor could go a little higher but I'm already in the top hole and cavitation plate is about 3.5" above the keel. I'm not that interested in top end anyway, and normally run a 15x15 4B PowerTech that jumps on plane very quickly at less than half throttle with a total weight of about 4000 lbs!

That V-20 is a very hard riding hull, one of the worst built I've ever seen (I personally know of 5 that have busted up running offshore here), and I don't think it's nearly as efficient as a SeaCraft. From my experience, I think a properly rigged SC20 can easily break 50 mph with about 175 hp on a bracket.

Re: rebuilding/repowering a 20' center console
 

I emailed Bay Mfg. and while they don't have anything now, they advised that they were working on it. They couldn't say how long it would be, though. [img]/forum/images/graemlins/tongue.gif[/img]

Re: rebuilding/repowering a 20' center console
 

Quite right Denny. I used to run a 2.0L Mercury XR4 150 that was balanced to .1 gram of reciprocating weight during re-manufacture, and got aftermarket reeds and re-jetted carbs, along with a nose-cone and low-water pickup. This motor dyno'd 193 hp on a hydro-dyno.

With my Seafari, (which is heavier than a MA or SF), this motor, and no bracket, once I got it propped right, even with my ablative bottom paint I could just touch 54 mph in the right conditions. I believe with a Hermco bracket I could have achieved 57, possibly 58 mph. (The motor did suck fuel at a prodigious rate, though, at anything over 5600 rpms)

The current Etec 175 reportedly actually produces between 188 and 195 hp at the prop. (The Etec 150 about 165 hp). So with the right prop, a nose cone and a bracket, it should easily reach 55 mph on a 20' SF with a slick bottom. And cruise at over 3.5 mpg, too.

Of course, with my 90 Optimax, I still cruise at 24 mph, but get over 5 mpg :cool: :cool:

Re: rebuilding/repowering a 20' center console
 

Frank,
I thought the 150XR4s were all 2.4L. My '91 XR4 is. I just assumed the XR2s were 2.0L, the XR4s were 2.4L and the XR6s were 2.5L. Not so?
Dave

Re: rebuilding/repowering a 20' center console
 

Nope. My XR4150 was a '90, with large gearcase lower unit off a '96 225. The XR4 150 up to and including '91 were definitely 2.0L, (as was the regular 150 and 135 V6, but the '88-'91 XR4 200 motors were 2.5L, as were the 150-175-200 XR6 motors which came out in '92.

Of course, there exists the possibility that I'm completely wrong. Tim (BigShrimpin') would be the authority on this. I know a lot more about the pre-'88 Merc inlines.

Re: rebuilding/repowering a 20' center console
 

I just took some photo's, how do I post them now?
Thanks,
John

Re: rebuilding/repowering a 20' center console
 

John, you first need to open up a free internet account on some site (Photobucket is a good one many of us use) that allows you to upload the pictures from your computer to that site. It's actually a good way of backing up important pictures to prevent loss due to a hard drive crash, etc., and you can then get to them from any computer with internet access. Checkout this post from Capt. Chuck in the Photos section that provides step by step instructions. It's real easy once you learn the process. Denny

Re: rebuilding/repowering a 20' center console
 

Thanks for the input on photo's, I just set up a photobucket account,here's a couple of pictures

[image]http://i1190.photobucket.com/albums/z454/jfc6866/th_100_0296.jpg?t=1297280175[/image] [image]http://s1190.photobucket.com/albums/z454/jfc6866/?previewTheme=84&track=interstitial&previewCancelU rl=http%3A%2F%2Fs1190.photobucket.com%2Falbums%2Fz 454%2Fjfc6866%2F#!cpZZ2QQtppZZ20[/image]

Re: rebuilding/repowering a 20' center console
 

Lets try again
http://i1190.photobucket.com/albums/...6/100_0296.jpg

Re: rebuilding/repowering a 20' center console
 

http://i1190.photobucket.com/albums/...6/100_0301.jpg
http://i1190.photobucket.com/albums/...6/100_0305.jpg
http://i1190.photobucket.com/albums/...6/100_0303.jpg

Re: rebuilding/repowering a 20' center console
 

Some older shots, stripped down no stringers
http://i1190.photobucket.com/albums/...0330091609.jpg
new stringers (divinycell)
http://i1190.photobucket.com/albums/...0414091238.jpg
Fuel tank compartment and foam in flotation
http://i1190.photobucket.com/albums/...0422091636.jpg
Nidacore deck
http://i1190.photobucket.com/albums/...0428091118.jpg

Re: rebuilding/repowering a 20' center console
 

some older shots
Bare Boat
http://i1190.photobucket.com/albums/...0330091609.jpg
Divinycell stringer
http://i1190.photobucket.com/albums/...0420091415.jpg
Nidacore Decks
http://i1190.photobucket.com/albums/...0428091118.jpg

Re: rebuilding/repowering a 20' center console
 

OOPs, sorry, I posted it twice, didn't see it the first time because it was on a 2nd page, will get better at this as I go.