I just got my 1974 9.9 Johnson back from service where they replaced the points and contacts because it wouldn't start or even try to fire. It's also got a rebuilt fuel pump and brand new spark plugs. The boat will start in 4-5 pulls and runs good at lower/mid rpm, but when I give it full throttle it never full winds out, feels like I am missing out on the upper 1/2-1/3 of the power band. What should I check?
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9.9 johnson upper rpm hesitation
- Thread starter rpijan
- Start date
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I have the same motor a 1974. My issue may not be similar, but I have a heavy boat with a wood floor and weight distribution made a huge difference. If I moved up about three feet. The boat would rev up, pick up speed, and reach higher rpm's. If I moved back to the rear, the boat would lose rpms and slow down. For all of you out there who want to test my theory be careful. The 74 Johnsons had a kill button and not the red kill cord that would be later incorporated into everything.
This issue of weight distrubtion was solved by "souping up" the 74 with a 76 15 hp carb.
This issue of weight distrubtion was solved by "souping up" the 74 with a 76 15 hp carb.
PGRChaplain
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Sounds like the boat is too heavy or too much Pitch on the prop. Does the Boat Plane, (achieve a level attitude) or is the bow high while running?
Im having the same issue with mine bottom end is great till i open her up full throttle its still in the low rpm i have a 12 ft and just me gas tank and anchor the prop i have is a 3 blade with a minor knick in it and just had carb rebuilt new plugs etc
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- LOCATION
- Lake County, Central Florida
Do two things for me.
At WOT squeeze the primer bulb and see if that makes a difference.
At WOT quickly blip the choke and see if the engine momentarily picks up performance. (The engine will fall off then pick up when you do this). If it picks up past the original RPM then settles back down again this is what I am looking for.
Is it surging at all?
Does it have a "ragged" sound, as if it may be 4-cycling up at the range where you are having an issue?
At WOT squeeze the primer bulb and see if that makes a difference.
At WOT quickly blip the choke and see if the engine momentarily picks up performance. (The engine will fall off then pick up when you do this). If it picks up past the original RPM then settles back down again this is what I am looking for.
Is it surging at all?
Does it have a "ragged" sound, as if it may be 4-cycling up at the range where you are having an issue?
