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Author Topic:   Jackplate for montauk
scottfarm posted 02-25-2002 08:56 PM ET (US)   Profile for scottfarm   Send Email to scottfarm  
Every time I tilt my 75 merc up for transport the carborators drain some fuel into the motorwell(what a mess). Does any one else have this problem. Thinking of putting a 6" jackplate to move the leak in back of transum. Any performance increase would be icing on the cake. Has anybody got more speed using a 6" jackplate.
tabasco posted 02-26-2002 12:27 AM ET (US)     Profile for tabasco  Send Email to tabasco     
BigShot is the king of Jackplates :-)
jimh posted 02-26-2002 12:34 AM ET (US)     Profile for jimh  Send Email to jimh     
Does fuel drain from outboard motor carburetor when engine is tilted up?

Yes, it does on my 5-HP FORCE, but I don't think I've noticed this on my other carbureted engines.

Does a 6-inch setback/jackplate increase performance?

Yes, that is the claim, but I cannot cite any specific case of reported speeds before and after. People often change many things at once, including engine height and propeller, which can also affect performance.

By the way, fuel leaking into the water is a potential fine for pollution.

What horsepower and year is your engine? A "75 merc" could be a 27-year old motor or one rated 75-HP and made last week.

lhg posted 02-26-2002 01:05 AM ET (US)     Profile for lhg    
I think most of the old carbed engines will do that. My 115 Mercs do, a little. I just pull the fuel hoses and let them die out at idle, then they won't drip when tilted. Also prevents varnish build-up in the carbs from evaporating fuel.
scottfarm posted 02-26-2002 06:28 AM ET (US)     Profile for scottfarm  Send Email to scottfarm     
I never tilt the engine up while in the water, only when in transport. Will try to run out carbs. I saw a nice 6" onepiece-one bolt manuel adjustment jackplate at the boat show made by Vance(company in Tennessee) for $190.00. Have been looking around and this price seems to be the best.
Clark Roberts posted 02-26-2002 08:16 AM ET (US)     Profile for Clark Roberts  Send Email to Clark Roberts     
Dennis, as I recall you are running engine high on transom already, Doel-fin, and swinging a tall (21" ?) stainless prop and hitting approx 45 mph per gps... that about right? If so then you are getting the most out of 84 cubic inches/75hp of anyone I know so maybe the jackplate won't give you a substantial increase in top speed. I have had lots of the big bore 3 cyl Mercs (just installed a 71 cubic inch 70hp on my 15) and none dripped and I believe that there is a recovery sys for any dripping in the airbox. Check that airbox cover gasket is intact and replace/repair if necessary (sometimes the lower two screws are not replaced due to tight clearance). My suggestion would be to install the 6" jackplate and fiddle with engine height... you may get more speed and less draft! Watch that cooling water press (your engine has a seven hole water intake so you may want to plug the top hole on each side to prevent it sucking air... just a thought). Happy Whalin'.. Clark.. Spruce Creek Navy
scottfarm posted 02-26-2002 08:39 AM ET (US)     Profile for scottfarm  Send Email to scottfarm     
I've got 131/4 X 21 stainless propco prop with 1995 75hp merc with a doel fin. With 31 gallons of fuel I get about 40 to 41 mph straight and level. I can trim more and the boat starts porpoising but my speed goes up to 44 to 45 mph. I was wondering with the jackplate could I get 45 mph without the porpoising. Is the porpoising caused by motor being a hair too low. With the jackplate I could really fine tune the height. Is 6" the right setback for the montauk. Thanks for the airbox gasket tip, will check it out.
WhalerAce posted 02-26-2002 09:30 AM ET (US)     Profile for WhalerAce  Send Email to WhalerAce     
Considering the horsepower we have in this post (tobasco, clark, lhg, et al), I enter this discussion with no little trepidation, but addressing Larry's remark of draining the carbs -- are you not worried about one carb running out of gas before another one and those particular cylinders not being lubricated? Just a thought.

Ace standing by.

WhalerAce posted 02-26-2002 09:31 AM ET (US)     Profile for WhalerAce  Send Email to WhalerAce     
Oops. And of course JimH. Sorry. ;-)
jameso posted 02-27-2002 03:35 PM ET (US)     Profile for jameso  Send Email to jameso     
Clark, when can we get the performance #'s for the 40 to 70 repower. I am still looking for a 70 OMC for my 15. My regards to the little lady.
Jim Armstrong
Bigshot posted 02-27-2002 03:43 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
My 15 with a 70 did 48.6mph on a GPS with just me and no plate. I did have her high on the transom and swung a 13x20" SS Suzuki prop. I also had bottom paint. You use a plate and no paint and you'll break 50. I imagine the 40 would do about 35mph.
Clark Roberts posted 02-27-2002 08:17 PM ET (US)     Profile for Clark Roberts  Send Email to Clark Roberts     
Jim, the 40 Merc (4cyl) was mounted on a Bob's Machine MJ-5 (manual jack 5"setback) up about 3 inches, swinging a 14" pitch Yamaha stainless prop and would hit 35mph with light load (bigshot nailed it on the nose!). The 70hp is mounted on the same jack plate and up about 4 inches swinging a 20" pitch Quicksilver High Five stainless prop and it will hit about 50mph per gps at 5600rpm (had some more revs on tap) and trimmed out. I couldn't get an exact reading as the wind blew the coffee out of my cup (really did)!
I don't plan to try for absolute top speed by putting on my 22" pitch prop because, according to my neighbor in a chase boat, there was virtually no hull in the water so things could get out of hand! I plan to use due caution and run it easy and maybe up to 40 if I get in a hurry.
Clark Roberts posted 02-27-2002 08:27 PM ET (US)     Profile for Clark Roberts  Send Email to Clark Roberts     
Dennis, a 5 to 6" setback should work fine! Sonia and I will be on Cape San Blas next October. I had some Spruce Creek Navy - Gulf Coast Div. decals made up and will bring you one! "Hi" to Olga! Happy Whalin'.. Clark.. Spruce Creek Navy
scottfarm posted 02-27-2002 08:59 PM ET (US)     Profile for scottfarm  Send Email to scottfarm     
Thanks a million Clark. Will get up with you. We're staying at mexico beach for a week in may and will probably stay a week in nov. I like the off season-no crowds at the ramp.
vdbgroup posted 02-28-2002 12:05 AM ET (US)     Profile for vdbgroup  Send Email to vdbgroup     
I use a 4" inch setback manual two piece jackplate from CMC Mfg.

I use it to fine tune. You will need to re-cup your prop for better grip. Or if you go way way up, you will need a 4 blade prop.

Main reason, I got my jackplate was to get weight further back, ease of vertical adjustment, and better trimout. I prefer the Montauk to squat a little as it helps with chop. Also, note that your steering cable will be at a greater angle aand more stressed if you use a 6" setback. You may need to get a longer cable. Caution here.

Salmon Tub posted 03-08-2002 12:45 PM ET (US)     Profile for Salmon Tub  Send Email to Salmon Tub     
Hey Scottfarm, have you tried pulling the fuel line at the end of the day and either letting the engine idle out the remaining fuel in the system. I had almost same problem where while stored, on hot days, fuel would expand and through whatever path it took, would drip slowly out through exhaust. Now, after each use, as I flush engine at wash down, I just pull the fuel line and let the engine use up the remaining fuel in the system. This is actually recommended so if prolonged storage, fuel does not evaporate in carbs and leave film. Once it starts to die, hit the choke for a sec., and once it dies, fire up 1 or 2 times until it won't start.

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