Why does my mercruiser i/o motor only go idle speed and rev higher and higher as I put the throttle down?

Question

My friend was driving the boat and had it almost full throttle. I told him to cut it (throw the throttle into neutral) when we got to the no wake zone. He pulled the throttle back to far and accidentily went into reverse. We heard a big clunk, and I new that the gears or maybe something in the lower unit got damaged. The boat still goes into forward gear but will only idle very slowly. As I push the throttle down the engine will only rev higher and higher. Also reverse gear still works fine. It seems to be only the gears above idle speed. I guess my real question is how much money in repair work am I looking at? My boat is a Chaparral 2100SX with a Alpha mercruiser V8. I think it is a Chevy 302. Any feedback would be helpful. Thanks

Answer 1

This is the exact reason why I don't allow inexperienced individuals to ever operate my boat controls.  There are too many easy mistakes that someone not familiar can make to cost big money to repair.

Looks like you're going to have quite a big repair bill.  Throwing a boat or PWC into reverse while at speed (more than 5 to 8 mph), is extremely stressing on the drive system which could get wrecked, and you could possibly flood the engine as well.

Anyone I trust wishing to operate the boat must be legally qualified to operate it, must be supervised by me 100% of the time, and follow directions down the letter.  Else they get to sit and watch, or get kicked off the boat.

The skipper is always responsible for the vessel and its passengers' safety, so keep that in mind before handing over the controls to someone you aren't 100% confident in handling the responsibility.

Answer 2

Sounds like you have damaged the forward, or the pinion gear.  Drain the gear oil, and look for metal filings/pieces.  Another possibility is that you have spun the hub in the prop.  If your prop has a flo-torq hub, you will be able to see the damage.  If you have internal damage in the lower gearcase, rebuild price will be somewhere between $1200-$2500.  Sorry for the bad news, good luck

Answer 3

Bummer.

Jim has the answer, my first thought was gears damaged or spun hub.