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Bought a 2003 180 Ventura w/2003 125hp 4cyl 2 stroke Merc Saltwater series outboard on it. Not sure if original but seller said it was.

Used 1 year & when Merc throttle is pushed forward it takes a few seconds for prop to kick in & then it lurches.

Also when at higher speed, you must hold the throttle forward or it just eases itself back slowing down unless you hold it.

It was suggested by our mechanic possibly wrong prop is on it. I removed it & it is an aluminum 3 blade thru hub exhaust. Searched for manufacturer name & #s. Could find no name but found 2 numbers. 1 on flat part of blade where it is attached to hub 25187 & 1 on the 15 slot spindle 825075. Cannot find any diameter nor pitch #s. Measured from center of hub to outside tip of blade then multiplied by 2 & that equaled 12 & 1/2 ".

Have not looked at tach max rpm @ full load. Wondering if anyone knows what size/pitch/blade # AL prop would provide the best overall performance level for this boat/motor configuration?

[Moderator edited for clarity]

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When was the motor last serviced? If more than 2 years I suggest changing filters and spark plugs and have carburetors cleaned.

Throttle friction is adjustable at the binnacle (box with throttle handle). Under the cover there should be a screw to adjust.

To test prop, you need a operational tach. Install and water test the boat with a light load. Track speed with GPS.

There are dozens of "correct" props. Need to know what you have and how it performs first.

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The Mercury 125 2-stroke is a 2 + 2 engine, that is it idles and runs up to 1800 RPM on just two carbs and two cylinders, then the other two come in as you accelerate past the 1800 RPM threshold. I've never driven one of these, but have the heard the additional cylinders come on strong, and it takes some getting used to. That could be what you are experiencing. I've heard the 125 is a strong engine, and considerably more powerful than it's 115 cousin on the same platform.

As for the throttle feed back, it could be either the friction adjustment in the control itself, or it could be an improperly adjusted throttle cable at the engine. The shift cable also has to be correctly adjusted for the thrttle cable to work properly. so check both.

Regarding the prop, it sounds like you've been given a cheap aftermarket model. possibly an old design, as those are not Mercury markings. When it comes to aluminum props, you want Mercury or Quicksilver (made by Mercury for sale by non-Mercury dealers, marine stores and online), period, for any brand engine also, in either three or four blade. I am convinced NOBODY else makes an aluminum prop that runs anywhere near as well. They are actually quite good, and even run well, and hold well, against the SS props up to 40 MPH speeds. If you want to stay with aluminum, strongly consider the brand new 4 blade aluminum design, called Mercury Spitfire or Quicksilver Nemesis. You have a fairly heavy boat with lower HP, and the four blades should give better performance and load carrying, with no loss of top end speed. The engine has a 2.07 gear ratio, so I would GUESS a 17", 18" (Mercury SS Vengeance) or 19" prop, depending how fast the boat is. If you can turn 19" pitch, the Mercury Laser II would be your best bet for top end speed. Mercury and Quicksilver both have prop calculators on their websites that help you determine correct pitch and prop to buy. Be sure to use that tool. You can also call Boston Whaler Customer Service, and they can tell you the prop recommended for your boat/engine combination.

If you have to go down to 17", the aluminum Spitfire/Nemesis would be your choice, undless you want to go stinless, than I would look at the 15" Stiletto, which runs like a 17 pitch prop (don't ask me why?)l

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Thanks fellas.
Phil T... serviced every year, plugs, filters, thermostat changed out new every year after running in Buzzards Bay at Cape Cod Canal area all season. The tach is operational 0-6000rpm, it has Teleflex steering, & max hp plate for boat says 150hp. Thanks, I'll look at binnacle.
Finnegan....OK yes that may explain that initial hesitation then surge! It does seem like a very strong platform, I believe my mechanic said they were known as the Towers of Power. I'll look at cable adjust & friction, thanks Thanks for prop heads up info as well. Have been told Solas & Rubex were best on market for durability, speed, & performance. Mechanic did suggest possibly going to 4 blade & as you say boat is quite heavy. Thank you again!

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I really don't like saying this, but I'm not sure that mechanic of yours knows what he's talking about with respect to Mercury engines and propellers. So I would careful about his advice.

The 4 cylinder in-line engine you have is the successor to the famous Mercury "Tower of Power". They were made form 1958-1988 and are an in-line 6 cylinder engine. As a competent Mercury mechanic he should know that. They look like this:

http://smg.photobucket.com/user/lgolt...6195894858

As for stating Solas after market propellers are better than Mercury OEM propellers, he's entitled to his opinion, but good luck on that one. Solas must be the brand he sells. There are thousands of boat owers and professionals that would disagree on that one. Merc props are also widely used on most other brand engines, particularly the big Yamahas from what I have seen. They are also widely sought out on the used market and hold their value better than any other brand. Mercury invented variable prop venting and the interchangeable hub system to accomodate all engine brands, now an industry standard. In the photo you can see the Mercury Laser II props I use on my "Towers".

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Once again, thank you Finnegan for clarification on "TOP" engine history & your opinion on props, we're trying to learn as much as we can about our boat/motor/operation/maintenance. Yours look like classics & in mint condition, obviously carefully maintained. Have gotten much conflicting info over the years from different mechanics & unfortunately it's frustrating because you'd like to depend on a "professional"'s advice especially when they say it with such conviction. We don't know much but have found ourselves scratching our heads more than once over some of the advice we've gotten or paid for service that was either poorly done or not done at all.
We will go to Merc/Quicksilver sites to get the answer to our original question which was what prop matches our boat/engine model/weight configuration. Makes perfect sense to match a Merc prop to Merc engine & believe Whaler always sells their boats with Mercs on them indicating their trust in Merc products.

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Finnegan,
Took your advice & not only called Boston Whaler but also went online & contacted a number of prop sellers for suitability, comparisons, availability, suggestions, prices. Wide range of responses as you can imagine!
Here was Boston Whaler's Chuck Bennett's response which was very helpful & gave me a starting point to work from while incorporating all your suggestions:
Hello Mr. Tarascio,

Please excuse the delayed response, vacation last week.

Boston Whaler originally shipped out a 3 blade 13" X 19" Pitch Black Max prop with the 2003 180 Ventura and the 125 Classic Mercury two stroke outboard.
We achieved a top speed of about 40mph@5250 rpm and it planed in about 5 seconds.

The rpm range at wide open throttle for the 125 Classic outboard is between 4750-5250rpm.

Below is some basic information on selecting a prop...
SELECTING THE CORRECT PROPELLER
Matching your boat and engine with the right-sized propeller can make a big difference in performance. For most recreational boats, it is a simple process.

Make the following test with a clean hull:
· First, you will need to determine how fast your engine should operate with wide-open throttle (WOT). You can find this information in your engine owner's manual. If not, your dealer can provide it to you. Outboard engines generally have WOT ranges of 5,000 to 6,000 revolutions per minute (rpm).
· Next, you will need to determine how fast your engine runs at WOT. Before you make the test, check to see that your propeller is neither dinged nor bent. Now, take your boat out on the water with a normal load and weight distribution and adjust the trim as you usually do. Run it with WOT. If you have a reliable tachometer, it will tell you how fast your engine is running. If your engine is running too slow, replace your propeller with one with less pitch. If it runs too fast, choose one with greater pitch. In general, one inch of pitch is equal to about 200 rpms. So, if your engine is running, for example, 400 rpms too slow at WOT, reduce the pitch of your propeller by two inches.

Some dealers will let you try out propellers and return them if you have not dented, bent or scratched them. Continue to try different propellers until you have one that matches your boat and engine. For an excellent propeller guide for Mercury engines, please visit the Mercury Marine website at: www.mercurymarine.com, and choose "Propeller Selector" from the dropdown menu.
Below is the information provided by the Mercury Marine Prop selector tool after entering the information that we achieved at the factory...

I hope this helps.

Regards,
Chuck Bennett
Boston Whaler, Inc.
(877) 294-5645

He then went on to recommend Black Max, Laser II, Spitfire, & Trophy Plus as possible considerations.
I concentrated on Quicksilver Nemesis AL 4 blade RH 12.8x19 & Mercury Spitfire Mercalloy 4 blade RH 12.5x19
Prices all over the map but found the above Spitfire for a great price($159.) & no shipping charges from Leaders RPM out of Kalamazoo Michigan, Scheduled to arrive Tues UPS, then should be in business. Thanks once again for your invaluable(to us) opinions Finn, greatly appreciated!
Rusty