115 MERC RPM question

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Wiboater6181

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I am looking at boat with 1999 115 2 stroke merc. Test drove it and it maxs out at 4800 RPM. Runs great otherwise. I was wondering if Mercury has a RPM limiter on newer motor now. WOT say this motor sould max out between 4750 and 5250. Should I be concerned?
 
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Dave1027

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Re: 115 MERC RPM question

No rev limiter. What size/type boat was this on? What size prop? What was the top speed? I would be leery. 4800 is low.
 
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Wiboater6181

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Re: 115 MERC RPM question

Its on a 17 foot Glastron fiberglass boat with a fish and ski package. Not sure about the pitch, I should have looked. Speed wise it topped out at 35 MPH, could have got few more out of if by trimming the motor some.
 
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Dave1027

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Re: 115 MERC RPM question

The max rpm is with it trimmed out. This boat should be able to hit 40 mph. Is the prop banged up? You can forget pulling up adult skiers if the motor only revs to 4800. May need to be propped down a bit for good acceleration. I got my 100 propped to max out at 5500.

Do a compression test on the motor before you buy it.
 
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Wiboater6181

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Re: 115 MERC RPM question

The motor is very good condition. One very minor ding in the prop, hardly any paint missing. Lower unit is in very good condtion as well. Prop show no sign of repair either.

Yeah, I was debating having the compression test done. I would have to take it in, I don't possess those tools. Probably worth the money.

Thanks for your opinion.
 
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Wiboater6181

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Re: 115 MERC RPM question

Hey Dave, do you know what the compression should be for this 1999 115 HP? Or is just matter of the difference between cylinder as I have read on other posts.
 
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Dave1027

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Re: 115 MERC RPM question

They should all be within 10% of each other.
 
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CharlieB

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Re: 115 MERC RPM question

Take a look at the installed height of the motor to the boat.

Trim the motor such that the A/V plate above the prop is parallel to the hull, measure the height of the A/V plate from the hull bottom.

Generally, you want the plate an inch above the hull bottom to reduce gearcase drag in the water. If there is a lot of set-back from the bottom due to transom angle/hull step/design, you may be able to raise the motor mount an additional one half to one inch. Excessive gearcase drag can reduce WOT RPM and top speed.
 
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