I recently purchased a '92 Johnson 8 hp outboard for my 12' Sears Jon Boat. The first few times taking it out it ran pretty good except at the top end speed; once it planed and nearly reached what seemed top speed, the rpms shot up almost as if it was in neutral.
My neighbor said he thought this was blowout (cavitation). No big deal at first, as a few mph was no big deal to me since I previously used a trolling motor to get around.
Today, it was doing this even at low speeds. In fact, from a starting position, I could turn to full throttle and it would cavitate almost immediately. However, I could go forward at low speeds and increase speed VERY slowly if only slightly giving more throttle. Even still, once it reached a certain rpm, it would cavitate (or this is what I am assuming it is doing).
The cavitation plate is definitely below the hull, so I can't imagine this is the problem. I tried different running the motor at different angles (placing the pin through 3 of the 4 holes), with and without a passenger, but no difference. The prop seems in decent shape as well.
What else can I try? Thanks!
My neighbor said he thought this was blowout (cavitation). No big deal at first, as a few mph was no big deal to me since I previously used a trolling motor to get around.
Today, it was doing this even at low speeds. In fact, from a starting position, I could turn to full throttle and it would cavitate almost immediately. However, I could go forward at low speeds and increase speed VERY slowly if only slightly giving more throttle. Even still, once it reached a certain rpm, it would cavitate (or this is what I am assuming it is doing).
The cavitation plate is definitely below the hull, so I can't imagine this is the problem. I tried different running the motor at different angles (placing the pin through 3 of the 4 holes), with and without a passenger, but no difference. The prop seems in decent shape as well.
What else can I try? Thanks!
