Older Merc Motor Question

[BigBuckDown]

I have '91 Merc 115h and a 17' alumacraft phantom v170 bass boat which I wouldn't consider very heavy. Everytime I throttle forward to get the boat on top of the wake it bogs down in the back and it almost seems that my props spins out. I loose power and the motor revs real high. Does anyone have any clue whats going on. Once it gets up out of the water it runs great. I tried tightening the prop, got those wing stabilizers, and tried to move as much weight (batteries) to the front. I would think a 115 should push that boat right out of the water. Could it be something with the gears, or drive shaft? Thanks for any replies.

[laker]

It probably is a spun hub in the prop. Some merc props have a replaceable hub. Take it to your dealer. If it isn't replaceable you will need to get a new one.

[BigBuckDown]

Thats what I was hoping too but it's a brand new prop, It was doing the same thing as the old prop.

[laker]

I assume its a merc prop with the plastic hub? Did you assemble the prop correctly? Have a thrust washer ahead of it?

[BigBuckDown]

No it's not a merc prop. I checked to make sure everything was installed properly. It is the same prop as my old one. When I first bought the boat it wasn't doing it as bad, but now it is getting gradually worse. Could it be that the gears are stripped and not catching when it has to work to get above the wake. Thanks for your input Laker.

[blazer]

Check to make sure the pitch of your prop is correct for your boat size and weight.  I know that if you prop is not pitched properly for the weight of your boat you can over spin the motor.  Also, did you add any tranducers or anything else on the back of your boat.  This can cause the motor to run in dirty water, what I mean by that is that a tranducer mounted to close the motor can change the water flow to the motor and when you are running at higher speeds can cause the prop to run momentarily out of the water and cause you to lose speed.  Hope this helps.

[laker]

If your gears were stripped, you'ld know it. It wouldnt come out of the problem as you gained speed. Just get worse. I have seen worn driveshaft splines on the end that goes into the powerhead. But generally once they spin out they dont reengage. Take your lower unit down and check that if you suspect it. Also is your unit engaging fully? (going into gear all the way?) thats another possibility. Maybe your linkage needs adjusting. Another thing is to drain your gear lube and look if there are lots of filings. If you have a problem in there, there will be lots of them. And my best guess from what youve said is that it could be too small a diameter prop for the motor also, which would not bite well when you took off. What size are you running? Pitch and diameter both matter. Good luck.

[autocatt]

Is your motor setting to high on the transom. If it is to high you will not have any bottom end because your prop isn't getting enough water. It will be pulling air into the prop. The fin on your motor should be even with the keel of your boat. Some people raise the motor to gain more speed on the top end but there is a fine line on how much you can raise it without sacrificing something else.

[BigBuckDown]

I will look into the pitch tonight when I get home. I think when I went and bought my prop they looked up the year and model of my motor. Do I need a higher pitch for a heavier boat or does the pitch only matter for the motor's sake? The transducers have been on there since I got it. The fin does line up with the bottom of the boat, and I make sure that the trim is down when I engage. I will look into the prop situation tonight. Thanks much

[BigBuckDown]

The prop is 13X19 By Michigan wheel Co. I believe. Should I go with a higher pitch?

[lendo50]

my mrc does the same thing when i'm trim up to high be careful of the size of pitch you put on it  is your power trim working right i think it has some thing to do with dirty water like maybe your trans ducer board dirting the water

[Fish Guide]

sounds like a combo of wrong prop/pitch  and poor trim.  Does it act funny on abrupt high speed turns as well?  Do you notice more pull to one side vs the other?  Have you ever hit something hard with the hull or transom?  A messed up hull/transom could be causing "dirty" water as well.