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Author Topic:   17' Montauk Performance
DeepSouthWhaler posted 02-21-2004 10:33 AM ET (US)   Profile for DeepSouthWhaler  
I have a 1986 17' Montauk with all standard equipment including fuel tanks (twin aluminum 12s). The boat is powered by a 1995 90 Hp. Mercury 2s (3cyl). With 3 people on board, full fuel load and about 75 lbs of gear the boat tops out at 34 mph at 5200 RPMs. In reading various performance articles on this website, it seems that the boat should at least go over 40 mph. I am not sure what prop is on the engine. The prop came on the engine ( I bought is used.) The engine runs great and has been checked at a local Merc dealer. Any recommendations on prop size/pitch? The boat rarely has over 4 adults on board and I maybe ski twice a year.
jimh posted 02-21-2004 12:45 PM ET (US)     Profile for jimh  Send Email to jimh     
Your 90-HP Mercury is rated for 5500 RPM, and given the heavy load you report, I would say that you are properly set up with the correct propeller. You are able to turn 5200 RPM, which is in the correct range for the motor and under that load.


If you want to go over 40-MPH, you'll have to shed some weight and move up to a taller propeller. You'd be lucky to hit 40-MPH with a 19-inch propeller, and anything larger will probably not be suitable.

newt posted 02-21-2004 06:06 PM ET (US)     Profile for newt  Send Email to newt     
I have the same engine on my Montauk, only 8 years newer. With 3 people, fuel, and some gear I hit close to 40 mph. My prop is 21 pitch, but I can never remember the diameter..12.25" maybe.

While Jimh makes a good point about the RPM's being close to enough to your max RPM's of 5500 given the load in your boat, I still think you should be going faster.

Find out what prop you have, because a lousy prop will rob your performance. I know from experience that the inexpensive aluminum props - even if the proper size - aren't worth the money compared to a plain old Mercury Aluminum prop which is what I am running, and performs fine.

Mumbo Jumbo posted 02-21-2004 06:51 PM ET (US)     Profile for Mumbo Jumbo  Send Email to Mumbo Jumbo     

I ran a test on my 1964 Newport with two people, 75% full 27 gallon Pate tank, heavy poling platform, and 75 lb. of gear aboard. Two way GPS tests on smooth water (with and against current) yielded these results: 5200 rpms and two run average of 39.5 mph. The engine is a 2002 90hp two stroke Yamaha with a Yamaha stainless 17" prop.
JBCornwell posted 02-21-2004 06:57 PM ET (US)     Profile for JBCornwell  Send Email to JBCornwell     
You didn't mention how your engine is rigged or trimmed, DSW.

Optimum distribution of your weight, height of the engine and engine trim can be worth 5-6mph.

Set the engine so that your anti-ventilation plate is about 1" higher than the keel. If it is on a setback plate, add 1" of height for each 4" of setback.

Locate a good portion of the load behind the console.

Trim out to just short of porpoising.

Ideally set up, your boat should top out at 38-40mph @ 5500rpm with a 19" prop, by GPS. Do not trust speedometers; they are estimates at best.

Red sky at night. . .
JB

jmorgan40 posted 02-22-2004 09:46 AM ET (US)     Profile for jmorgan40  Send Email to jmorgan40     
I am not sure about the setup on a merc, I will leave that for some of the more experienced motor experts here. I know none have steered me wrong especially Sal. I have a 1986 Montauk with a 2000 90 hp Johnson. Prop is a 13.25 x 17 Stiletto. I am no lightweight, pushing 275 lbs. Was out Friday Striper fishing. Full tank of fuel 27 gallons, full livewell w/ 28 gallons and I was still able to get 41.3 mph on the GPS WOT and full trim running about 5200 rpms with a light chop on lake. And thats with my motor still needing to come up slightly which I can not pull off without a jackplate. But I have no need to go any faster. Top speed under perfect conditions was with both my son and I in boat and I get about 44 MPH at 5300 RPMs. Not sure why but I was able to get a little more speed out of the rig with an OMC SST prop at same size, 13.25 x 17. The stiletto is better out of the hole though and a better all-around prop, and besides it looks better. Not sure if any of this helps.
Joe
Matthew posted 02-22-2004 11:42 AM ET (US)     Profile for Matthew  Send Email to Matthew     
Make sure that your tach is giving you correct readings. If it is original to the boat it has a few years on it.
Matt
jmorgan40 posted 02-22-2004 12:16 PM ET (US)     Profile for jmorgan40  Send Email to jmorgan40     
Matt,
There is nothing wrong with my tach. All brand new Faria guages. New Faria tach w/ System Check less than a year old.
Landlocked posted 02-22-2004 09:04 PM ET (US)     Profile for Landlocked  Send Email to Landlocked     
My 2002 Merc 90 2stroke / 77 montauk combo is getting around 42 mph max (gps) at 5,250 rpm with just me on board and 2 12 gallon tanks of fuel. Motor is mounted with 1 hole showing. Cavitation plate is about 1.25" above bottom of keel. Prop is 21" Merc black max aluminum.

Its important to note that while I can get the 42 mph, I rarely do. Boat is really squirrely at this speed. Boat feels most comfortable running mid 30's.

Ll.

Bigshot posted 02-23-2004 01:58 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
i would check the tach...I NEVER trust aftermarket gauges except Gaffig or other top of the line.
Ranger Rick posted 02-23-2004 02:05 PM ET (US)     Profile for Ranger Rick  Send Email to Ranger Rick     
How do you go about checking your tach? I need to do this for peace of mind before I start dinking with my setup.

Thanks!

~Rick

Bigshot posted 02-23-2004 02:23 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Try another one or use a portable one from a mechanic to test. I put a teleflex tach on my 30 Yamaha and it always read too high....frustrating.

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