Get instant online access to repair manuals for your Mercury / Mariner outboard. Online Manuals
Order printed Mercury / Mariner service manuals — shipped to your door! Printed Manuals
Use engine diagrams to find & order parts for your Mercury / Mariner engine. Engine Diagrams
Find parts quickly with Mercury application guides. Quick Parts Guide
Results 1 to 3 of 3
  1. #1

    Default Bogging under load - 09 Merc 30 EFI fourstroke

    Hey all, new to this forum.

    Just bought a used boat about a month ago and I knew it needed some tlc.

    Changed the impeller and that solved my over heat alarm

    New prop as the old ones were suspect, seems like the prop shaft is sligtly bent, but everything shifts quiet and flawless. No shake or cavitation at wot

    Lower unit holds pressure and has new gear lube.

    New fuel pressure reg.

    Tore open the low pressure fuel pump and looks new.

    The vst tank was pretty clean, tore that open and cleaned the hp fuel pump screen. And ultrasonic cleaned all the parts.

    Spark plugs look clean.

    Compression is about 95 on all 3 cyl

    Checked fuel pressure - stays around 40 psi at rail

    The boat really runs and drive pretty much without flaw, but issue I have is loss of power wot. If it is just me on the boat, I can get it to slowly build rpm from 4200 slowly build to 6000 and get 20+mph. If weight gets shifted to the back of the boat it will bog down and lose power. Power loss also occurs on turns at wot.

    Originally thought it was running in limp mode, then got it to get on plane and moved my train of thought to fuel issue. My concerns with fuel is that it runs without hiccup, except bogs under load, esp when weight is at the Stearn.

    Any ideas would be awesome. I'm to the point where I probably have to show a mechanic, because I'm at wits end
    Last edited by Jkrau1; 07-13-2020 at 09:19 PM.

  2. #2
    Join Date
    Mar 2019
    Ottawa Canada

    Default Re: Bogging under load - 09 Merc 30 EFI fourstroke

    is the vent open on your fuel tank?

  3. #3

    Default Re: Bogging under load - 09 Merc 30 EFI fourstroke

    Quote Originally Posted by mechanicman View Post
    is the vent open on your fuel tank?

    I have not had a vacuum issue, the flow of fuel seems good from the pickup to the vst

Similar Threads

  1. bogging 4.3 under load
    By darrellbierback in forum Mercruiser Sterndrive Forum
    Replies: 6
    Last Post: 07-14-2017, 12:45 AM
  2. Motor bogging under load
    By molyneux in forum Honda Outboard Forum
    Replies: 7
    Last Post: 06-21-2017, 09:11 AM
  3. 2007 Mercury 60hp fourstroke EFI in Guardian mode under load.
    By scy in forum Mercury Mariner Outboard Forum
    Replies: 2
    Last Post: 06-08-2017, 01:30 PM
  4. Bogging down under load
    By greg youmans in forum Johnson Evinrude Outboard Archive
    Replies: 1
    Last Post: 04-21-2008, 10:51 PM
  5. 225 OX66 bogging under load
    By Jimmy Z in forum Yamaha Outboard Archive
    Replies: 6
    Last Post: 11-16-2007, 09:41 AM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts