Mercury 9.9 2 stroke 3 blade vs 4 blade

williev31

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Re: Mercury 9.9 2 stroke 3 blade vs 4 blade

I got out to the water today with the tach in place. With just me in the boat I got 16mph at 4700rpm, and took about 200yrds to hit plane. When my son, niece, nephew, all about 70# got in with me we dropped to 11mph and 4100rpm, and never got up on plane. Looks like if im going to keep this motor as a spare a new prop might be in order. So back to the original question, should I just stay with a 3 blade and just drop to a 8" pitch, or would I get any benefit from a 4 blade prop. If so should I go 8" or 7" pitch on the 4 blade.
 

Mi duckdown

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Apr 14, 2007
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Re: Mercury 9.9 2 stroke 3 blade vs 4 blade

Make sure your motor and transom height are correct. TOO ME From that Bad Pic. it looks like you have a short shaft motor 15" on a 20" transom. 02
 

williev31

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Re: Mercury 9.9 2 stroke 3 blade vs 4 blade

The grizzley 1448 has a transom cut out and takes a ss motor. The av plate is an inch below the bottom of the boat, if anything the motor could come up a bit.
 

steelespike

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Re: Mercury 9.9 2 stroke 3 blade vs 4 blade

A decarb treatment might give you some more compression.
If your sure about the tune of the motor and sure the throttle opens all the way I think a 8" 3 blade is a good choice.
it will improve hole shot and should get you on plane with a load.
 

MikDee

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Re: Mercury 9.9 2 stroke 3 blade vs 4 blade

Here's a few tips to try, & get the most from your motor. Make sure to run that motor trimmed up as high as you need, to keep the prop as parallel with the bottom to get full thrust.

Are the idle mixture screws set as rich as you can?

2-cycle motors like to run a bit rich, it's healthier for the motor, then running lean. Take note of the number of turns the screws are out from lightly seated now, then back them out 1/4 turn at a time to the highest idle, then take them out in 1/4 turn increments, till the engine starts to slow down, that should be your best, & safest idle adjustment.

If you're engine is not running the top of it's tune, this should help. A decarb with Seafoam may clean out excess carbon freeing up your rings, if there is any build up.

Next after running for a long time, check your spark plugs, (let them cool down first, so there's no damage to the head threads) then see if they look wet, or carboned up at all? If so, you could probably get away with the next hotter heat range spark plug, if changing plugs, make sure to try, & get Resistor plugs to keep your spark at the tips,,, otherwise you might get external arcing, or cross firing, stealing your spark.

Next, with the engine off, check to see if your carb butterflies are opening fully at W.O.T. (wide open throttle), and finally check your link & synch. now (if carbs, & ignition advance are still synchronized) throughout your throttle range.
 

Sea Rider

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Re: Mercury 9.9 2 stroke 3 blade vs 4 blade

You're asking too much out of that 9.9 engine for such large alum boat, with that engine just for light loaded 1 2 men use. Useless to buy a 4 blade prop unless you want to throw money into the blue. That engine runs 5-6 K wot, Get yourself a larger min 15 HP or pass your current 9.9 to 15, both models shares same 250 CC.

The conversion on that model, could be costly. Will need to change carb, reed valve assy and gaskets. Moons back converted my old 96/9.9 to 15 and the difference was awesome, could carry more load with better top speed.

Playing with pitch props probably useless, will need several lower pitch props to raise wot rpm from 4700 to at least 5500 middle wot rpm to be at safe side. Check correct engine/transom height and trim but that's with a 100% healthy engine, don't know about yours. Useless playing with fuel/air screw on carb, that's only for best idle speed, once paasing idle circuit, the carb mixture is fixed and non adjustable. Untill you don't find the direct cause to have such a low and poor wot rpm, don't wot that engine you're extremely lugging it even with you alone and assuming tach works & reads accurately.

Happy Boating
 
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steelespike

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Re: Mercury 9.9 2 stroke 3 blade vs 4 blade

If the 1448 is a bare bones boat it will plane easier than a smaller narrower boat.1448 is the size boat the 9.9 was intended to push.
Now if its loaded with a floor, live wells , extra batteries and fuel , other weight adding devices and a couple of 300 pounders thats another story.
Your still better off with a bare 1448 than a smaller narrower boat.
 
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Sea Rider

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Re: Mercury 9.9 2 stroke 3 blade vs 4 blade

If the 1448 is a bare bones boat it will plane easier than a smaller narrower boat.1448 is the size boat the 9.9 was intended to push.

Don't know that model boat, by push you mean literally push or achieve full plane with nice speed with a 9.9 engine. An updated same 9.9 to 15 will push and or plane much better and faster including moving heavier loads.

Happy Boating
 

steelespike

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Re: Mercury 9.9 2 stroke 3 blade vs 4 blade

1448 is a 14 ft usually a jon with a 48" wide bottom.The length alone will help it get the bow down when trying to plane.
The somewhat larger footprint will get a load up easier than a 1236 or 1436 or even a 42.
As far as a 9.9 or 10 We had a 57 14 ft Crestliner utility, rated for 35 hp. with a 57 10 hp Johnson I was 14 and we played with trim and basic setup. moved people around etc.The boat would plane fairly quickly with 2 of us 100 pounders on the back seat and the motor trimmed out all the way out out.Of course we soon became bored with the bounding bow.
Being a 57 the motor it was rated at the power head probably really a 9.
Considering a 9.9 is rated for about 21 mph lightly loaded his latest speed doesn't seem un reasonable.
I think dropping down to a 8" prop could add 300 to 400 rpm.
little motors are more responsive to a prop change.
 
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williev31

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Re: Mercury 9.9 2 stroke 3 blade vs 4 blade

Well I took the plunge and put the 9.9 on craigs list, it sold in 6 hours. I went to pick up a 2009 merc 15hp 4 stroke today. Got it mounted just in time to go to work. I should be able to put it on the water tomorrow. I will give an update, Thanks for all the help every one.
 

Sea Rider

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Re: Mercury 9.9 2 stroke 3 blade vs 4 blade

Well I took the plunge and put the 9.9 on craigs list, it sold in 6 hours. I went to pick up a 2009 merc 15hp 4 stroke today.

Congrats, the very best you could ever made, the 15 definitely should give you more boating joy and extra diversion. Check that the 15 seats at sweet transom height match for optimum performance.

Happy Boating
 
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williev31

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Re: Mercury 9.9 2 stroke 3 blade vs 4 blade

Update, I just got back from a test with the new motor. What a difference, 22mph @5400 rpm. Seems like the rpm is a little high at wot but I I can back off the throttle once up on plane and maintain 20 mph at 1/2 throttle. It has a 9" pitch on it now and im going to try some loaded runs, if it still hits the rev limiter I may look into a 10" pitch. Thanks all and happy boating.

PS it just looks better now too

100_4062.jpg100_4060.jpg100_4061.jpg
 

Sea Rider

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Re: Mercury 9.9 2 stroke 3 blade vs 4 blade

WOT for that model is 5-6 K, if at 5400 you're just in middle and fine. If having a rev limiter, should kick around max rpm. If you add extra load current wot rpm will drop accordingly. Try not lo lug that engine at wot if adding more load or extra boaters, if so will probably need to go to a less pitch prop to raise revs a bit and be at near middle range again.

Happy Boating
 
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