Re Propping 83 Merc on 72 Seafari
 

Greetings all. Wealth of knowledge here. Hopin to gain some so I can share it down the road. I'm newly registered and the proud new owner of a '72 Seafari. This baby came with an 83 Merc 115 in pretty good shape. I've rejetted carbs have adjusted timing to hopefully better burn, cool and cope with modern ethanol. Prop appears original but I'm guessing there are better modern prop sizes, shapes, etc., to maximize fuel efficiency and overall performance. My offshore M.O. is to cruise in search of working birds, temp breaks, and kelp paddies, then drift or troll depending on what's happening. Could any of you esteemed seafarers shed a little light on the right prop. I know it's not exactly a gas miser but I'd like to run this motor for at least a few years while saving to repower this old girl so re-propping for fuel efficiency is my primay goal. Thank in advance for your opinions. -- McGillicuddy :cool:

Re: Re Propping 83 Merc on 72 Seafari
 

Welcome to the site! You're the 2nd Seafari owner to sign up in the last week or so! I've owned my '72 Seafari since 1975, mostly all original except for recent repower. If you'll send me a PM w/e-mail address, I can send you some files of brochures on that model.

I ran a 115 V-4 Evinrude for 31 years. Not fast, but was a light motor that made for a good well-balanced (not stern-heavy) combination that ran well offshore where you can't run much over 20 kts anyway when it gets rough; best prop for me was a 13 3/4 x 15P SST (cupped stainless) with cav plate raise about 1" above bottom. I averaged about 2.8 mpg over 6 trips to the Abacos, but it dropped to about 2 mpg after power trim died. It would turn 5400-5500 with a heavy load. That was rated rpm for that motor; you want to make sure motor will turn up to max rated rpm for your motor with the typical load you plan to carry. Don't know what the rated rpm is on the Merc. A couple other members on this site also run this size prop with a much newer 115 johnrudes. I tried a 13.25 x 17P, but it wouldn't turn enough rpm with the heavy load I typically ran. Newer prop designs may perform a little better but this size should get you in ballpark, assuming your gear reduction is about 2:1. Fr. Frank could probably give you better advice on Merc props. Denny

Re: Re Propping 83 Merc on 72 Seafari
 

Thanks for the welcome bushwacker. I picked this girl up the week of the California wildfires just north of Malibu. I saw a beautiful Sceptre 23 for sale in Ventura but didn't think I could pull it with my Toyota T100. Then I saw a 20' cc with a pretty new Optimax in Orange County, CA but I wanted a cuddy so I hesitated. I had never seen the Seafari but when this one popped up on LA craigslist I was pretty sure God was talking to me, saying, "go get it, boy"... I'll try to post a pic but I'm not sure how just yet. I have some concerns as I begin to restore it but for now its ready to test ride (gotta put in a VHF this week or next first though). Sorry about the big pics - couldn't figure out how to resize for economy posting. Thanks again for the welcome.
http://i261.photobucket.com/albums/i...therapist1.jpg
http://i261.photobucket.com/albums/i...eacraft010.jpg
http://i261.photobucket.com/albums/i...eacraft024.jpg

Re: Re Propping 83 Merc on 72 Seafari
 

Hey Another California Seafari!! Very Cool!!

Re: Re Propping 83 Merc on 72 Seafari
 

Denny's pretty close. Something on the order of a 13x15 cupped SS should be close. SS is much better for offshore. Don't use the Quicksilver Laser II, though, as it's designed as a bow-lifting prop and you need more sternlift. The Vengeance series is okay, but just okay. The old SS Black Max props (no longer made in SS) are better, or best, IMO, the PowerTech M135 series in a 15P.

Denny's right about the mounting position, too. Bottom of the engine cavitation plate about 1" above the keel line with the motor at neutral trim (parallel cavitation plate and keel line)

As an "old hand", I'm gonna throw some useful info at you, but it'll be a bit wordy.

The inline 6 "Tower of Power" Mercury motors are fantastic motors and nearly bulletproof when cared for, but there are some idiosyncrasies to worry about. Never, Never run these motors between 6200 and 6900 rpms - they'll self-destruct quickly from engine harmonics. (Believe it or not, running higher rpms than that is okay up to about 9000 rpms, as long as you run the right fuel-oil mix. Mercury Marine used to race these motors turning 8000 to 9000 rpms, making over 225 hp out of the 115/125 hp motors, and over 250 out of the inline 150 motors.) But these motors love to run at 5400 to 6000 rpms. I have owned no less than 9 inline 6 Mercury motors in my life, and still have an '86 115 in the shed.

I suggest you be very careful with the fuel/oil mixture, based upon your average rpms. If you run mostly over 4800, I suggest a 40:1 mix rather than 50:1 mix, that'll keep your top cylinder better lubed. However, if you run mostly below 4800, stay with the 50:1, or your spark plugs will need periodic cleaning.

Very important - make sure you have a good thermostat. With water temps below 70* and no thermostat, you'll burn fuel very inefficiently, and foul your spark plugs quickly because the motor won't ever get up to a good operating temperature. You can run without a thermostat in water above 80* in Florida in the summer if you have a brand-new impeller, but it's not a good idea, generally.

Speaking of that, make sure you change your water pump impeller every year, or every 100 hours, whichever comes first. This is another Very Important Procedure. Even if you only put 20 hours on the motor one year, change the impeller anyway. More inline 6 motors are killed from overheating than any other cause, and old pumps sometimes fail to adequately cool the top cylinder, especially if the thermostat is stuck open or missing.

Every time you run it in salt, rinse and flush thoroughly. Use Boeshield or Fluid Film on the motor liberally.
Run PowerTune through all three carbs while running in gear a couple of times a year, or run RingFree a couple of times a year.

It's a very good motor. It's also the genesis for the current Verados, because it's a naturally balanced motor.

Don't expect great fuel economy, but they're still better than the OMC motors of the '70 to '87 time frame, just nothing like today. Your cruising rpms for best economy with this motor will likely be near 4800 rpms.

Re: Re Propping 83 Merc on 72 Seafari
 

Hi guys,
Thanks for the pics and advice from the THT site, Big. Is that Bruce Brown video available - does it have a name?
I got the brochures, bushwacker, Muchas gracias!
Thanks for the words of wisdom, Fr. Frank. The more the merrier. Any thoughts on this transom - It looks like its center got cut down to allow for a shorter shaft. I think the current motor is a 20".
Someone tried to seal the cut with Formica and the glue has released so the wood is exposed. I was thinking I'd start by soaking it with some CBES then covering and shaping with mat and resin or Smiths building epoxy. I suspect I'll need to remove the motor to do this right and so I wonder if I should remove the aluminum plates too to make sure there's nothing wrong there. Any thoughts on this? Products, approaches? I'm a decent woodworker but not very experienced with marine f-glas, fillers or gel coat finishing techniques. Thanks again, guys. :cool:
http://i261.photobucket.com/albums/i...eacraft021.jpg

Re: Re Propping 83 Merc on 72 Seafari
 

Your transom looks like someone already replaced the wood in it, but had no idea how to seal it, which makes me wonder how good of a job someone did. The plates are an obvious attempt to strengthen a weak transom, and the Formica is a disaster waiting to afflict you. Yeah, you gotta pull the motor off to fix it. Your transom is scary.

If necessary, replacing the transom can be accomplished structurally in as little as 3 days, if you plan ahead. Cosmetics stuff I don't know about.

There's lots of information on that subject here at Classic SeaCraft if you search for it.

Re: Re Propping 83 Merc on 72 Seafari
 

Hi Fr. Frank, and all,
Thanks for the feedback. Bushwacker made some suggestions on products and approaches in an e-mail so thanks to you too, bushwacker. I kind of wondered about that transom fiddlin', because the material appears to be Fir or Cypress and shows a lap-joint. I was under the impression that the transoms on these things were lots of f-glass and resin over 1-3/8" ply., also the transom has been painted with something other than marine quality paint or gel coat as its faded and flaky. The transom is strong however -- and my mechanic and I both rocked on the motor pretty hard with no movement to the transom. I kind of think whoever cut down the transom & bolted on the aluminum plates did so knowing they needed to counter the loss of rigidity from messing with the original transom. Don't know why I give these guys the benefit of the doubt...? After all a lot of guys around here claim to be auto-body workers but they would have had a tough time passing a fifth grade pottery class...,heh, heh :D

By the way today I went down to work and I immediately noticed an old red Seafari 25 w/NY tags at my shipping terminal, apparently on its way to the Island State... Hope I haven't violated anyone's privacy but just in case I'll leave her name out of this...Never seen a 25 before. That's a lot of boat!!! -- G

Re: Re Propping 83 Merc on 72 Seafari
 

The Bruce Brown film was done for Seacraft back in 73 or 74 the title is called "a long way in a small boat". Trayder is the man to talk too about this movie, but I have some info that BBF might be helping Potter get the film restored. It's an amazing short film with awesome footage of 2 23's in some really nasty seas . . . it puts that tracker seacraft video to shame.

Re: Re Propping 83 Merc on 72 Seafari
 

another Seafari 20 owner chiming in - you will love that boat, and, contrary to what some will say, a 115 is decent power for her, she should top out around 30 - 33, more than you can run is open sea anyways. I wouldn't go beyond that motor-weight range, or the old Johnson V-4, without raising the transom to 25".

Fr. Frank is the man when it comes to the old Merc's, listen to him.

And as others have said, that transom work looks a little scary. If you say it's solid, for now, ok, but from the looks of it, I think you want to plan a transom rebuild, combined with raising to 25", within a few years, coinciding with the future repower.

Fun, and very capable, boat.

Bill