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  1. #1
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    2016 merc 4 stroke low rpm's

    2016 mercury 90 hp
    serial number 2B225259 ME90LSP

    I was out on a buddies boat he just bought and it was an absolute turd. Couldn't get up on plane and topped out 4400 rpm's the motor has 800 hrs on it and a compression test was never done. The motor sits on an 19' Lowe and prior to that on a pontoon boat. The prop is a beat up aluminum 17P 4 blade that was run on the pontoon.. The thing starts, idles and seams to run fine, just unable to push the boat up onto plane. Hard to believe it'd be as simple as dropping a pitch or two on the prop as this one seams small as it is. What do you guys suggest we do first? New plugs, filters and oil change recently performed with no change in performance.
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  2. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #2
    Moving your post to the 4-stroke Forum for you (it was posted in the 2-stroke 2.0/2.4/2.5L forum).

    This engine is a SEAPRO model, which has a lower maximum RPM and setup. It's designed specifically for commercial applications, durability and push-power (not so much raw speed setups).

    A good starting point is to verify the engine is up to date on maintenance, and running properly. THEN start checking into the setup.


    Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
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  3. Member
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    #3
    The motor was owned by an out of town marina where he purchased the Lowe with this motor on it. (The boat was a rental, they the marina swapped engines prior to selling it) After my buddy acquired it he had all the service done to it locally as he did not know what had or hadn't been done. I just looked up the RPM range and it's listed at 5000 - 5500 at wot. As mentioned he's turning 4200 with a 17P aluminum prop. There's nowhere locally to "try" props before you buy around here and he's only looking for an elcheapo to explore local waters with (aka aluminum) I just didn't want to see him do damage if his oversized prop was causing the motor to lug.. Assuming that is you guys feel the prop may be the culprit.. Would another 1000 rpms wake the motor up a bit? Should I do a compression test on the motor?

    Thanks again.. : )

  4. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #4
    I may be misunderstanding what "type" of 19' Lowe this is mounted to... probably wise to clarify that. If it's a fish/ski type model, it SHOULD be very close at 17P.

    Are we getting the RPM figure from an ANALOG tach or a Smartcraft Display (very important)?

    Have you verified the throttle is actually reaching the 100% WOT position?

    Let's clarify these first and then give some pointers/suggestions.


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  5. Member
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    #5
    It is a 17' Fish & Ski and the rpms came from his vesselview setup. Also I removed the cowel and had him move the throttle from idle to wot and it appears to be moving all the while he's moving the throttle. The linkage stops as soon as he says he's maxed out at the helm. I have a video of it running on the river and to me it sounds like it wants to take off for a a slit second every minute or two.. Kinda like something makes contact but only momentarily.
    .

  6. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #6
    Might be a good idea to make sure it's actually running on all 4 cylinders. Something as simple as a spark plug, coil, injector, etc.

    The G3 Diagnostic System has a feature that permits a Cylinder Misfire Test to be performed at WOT.

    Note: Just because linkage continues to move does not mean it's reaching 100% WOT. That needs to be checked with G3 and via verifying the mechanical stop is being reached on the throttle plate.


    Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
    Still consider myself a "Marine Apprentice" after 47 years (learn something new every day).
    Mercury Parts, Mercury Outboards, Smartcraft & Accessories, Injector Service, TDR Reeds- BBC Sponsor