Before Posting, Please Read Our Posting Guidelines Below.
1. Use the full 4 digit year for everything you are asking your question about. Example: 1962, 1988, 2000, 2011 2. Include the correct name of your Whaler model. Example: Montauk 17, Montauk 170, Outrage 26, Outrage 260 3. Include the length when necessary. Example: 16, 17, 18, 20, 22 4. Do not post your email address anywhere on this site as it is already in your user profile.
First year with a Boston Whaler and I am hooked
I have a 1979 Newport 17 commercial hull with a 1979 80HP Mercury that is still running strong turning a 13.5x17 aluminum prop, at top rpm I get 5000 for 32 mph with 3 people on board and 6 gallons of fuel.
Overall very happy with ride and stance of boat when trimmed right
Next summer I want to pull a tube or a wakeboard and was thinking taking advantage of year end sales.
Any thoughts on going to a 17 pitch prop
Thanks
It works the other way around, to get more punch out of the hole, you'll need a 15p. Anyways, it couldn't hurt to get a couple hundreds more rpm at WOT, as you're on the lower side at 5000, so with a 15p, you may get a better hole shot AND top speed... and keep your 17p as a spare.
Edited by saumon on 11/19/14 - 6:21 PM
1991 Outrage 17' I - 2005 E-Tec 90hp
As a Classic Merc owner, I am familiar with your engine, since it is 4 of the 6 cylinders of the in-line 6's that I have. Gear ratio is 2.33.
Referencing Mercury's prop charts for your engine, with a strong engine, and with 5500 RPM, you should be running 38-42 MPH. Before buying a new prop, I would see if your boat, MORE LIGHTLY LOADED, will do close to the 5500 redline, and achieve the speeds mentioned. If not, either the engine needs work, the prop is a poor or outdated design (whether it be an old Merc design or aftermarket prop), or the boat is much heavier than it should be.
My guess is that your engine is mounted too low (all the way down on the transom), and with the transom bracket design of those days (thumb screw clamps), not easy to raise up. But if you can do it, I would bring the engine up about 3/4" to 1". With that old design transom bracket, the best way to raise the engine is install a 6" setback jackplate (the anodized aluminum Teleflex/Detwiler is highly recommended), and buy the special adaptor needed for these old Mercs. Then you can raise or lower it at will, easily, and boat/engine performance will be maximized.
If not, a Mercury aluminum prop is your best bet, since I am convinced they are the best perfroming and holding aluminums you can buy. Since Mercury is indicating a 19" prop is right for your boat, for a first choice, and for better pulling power at the same time, the brand new design 4 blade "Spitfire" is recommended. For a little less, you can buy the "Black Max" 3 blade. Often when boating is saltwater, I use a pair of the 19" Black Max/Black Diamond on my classic 21 Outrage with pair of 115 "Towers", and the boat will do 52 MPH @ 5800 RPM, very fast for aluminum props. (engines have a different 2.0 gear ratio)
If you can succeed is raising the engine an inch or so, a 19" Mercury Laser II will be your fastest, best riding prop, but they are pricey. For less, the Stiletto 17" (runs like a 19") 3 blade Advantage could be a good choice. But only if you get the engine up. If not, and running the prop fully submerged, it's not likely a performance SS will give any better performance than the Merc aluminums considring your speed range of the high 30's.
I run a Merc Laser II on my jackplate mounted classic 1979 Merc 115 powered 1979 Montauk, and the prop is a screamer to say the least. Lightning fast acceleration, great hull lift and ride, and strong top end (over 50). (see personal website link)
Here is really good mail order source for Mercury props:
Finnegan,
Thank you for very complete and well explained options that I have to consider. Hard to do more test at this time of year, boat is now in storage, and yes the motor is all the way down.
Here is how much weight was in the boat when I verified speed with my car GPS .
3 people, 580lbs
2 bateries at stern 90Lbs
Fuel 60Lbs
Electric motor 15lbs
Motor 280lbs
gear 40lbs
Commercial hull 150Lbs of extra fiberglass
Total 1215lbs
Carbs will be rebuilt in the spring as well as moving the batteries to the console.
Not sure about spending money on a jack plate, this is already an older motor and who knows how long it will still run.
I will definitly invest in a 17 pitch prop, i expect it should give me a better hole shot for water sports, and I am not totaly unhappy with 32mph with a pretty loaded up boat and a 35 year old motor
Who knows maybe the wife will let me invest in a new Yamaha 70 at the spring boat show
Now all I can do is plan for the work I want to get done in the sping.
