Lost thrust while at cruise speed

[krudville]

I have a '94 4 Winns Horizon 180 SE 5 Liter with OMC Cobra outdrive, while at cruise speed it suddenly lost thrust and rpm went nuts. Got it shut down ok. Started back up, it goes into gear fine, forward and reverse and has thrust at low speed. As soon as I power up however I just get revs and lose thrust. Any ideas. Heck of a way to end the year. Otherwise beautiful day at Lake Chelan WA. Thanks for any feedback.

 

[airdvr1227]

Re: Lost thrust while at cruise speed

Several possibilities...could be your prop spinning on the hub...or the coupler from the drive to the engine (you'll usually see some smoke and smell something burning). Hit anything with your prop lately?

 

[krudville]

Re: Lost thrust while at cruise speed

No hits all year. Prop is secure.

 

[krudville]

Re: Lost thrust while at cruise speed

No smoke or noises at all. Drove back to the cabin at just past idle for 1.5 hours, worked fine.

 

[GMC2003]

Re: Lost thrust while at cruise speed

Sounds like a spun prop hub. Your prop may look and feel solid, but it might not be... I did the same thing a few months ago, but I was going from cruise to wide open. There are ways to check if you have a spun prop. I can't recollect them other than making a mark on both the prop and hub, then after it slips (rpm's shoot up) , check it and see if the marks are in the same place....

 

[krudville]

Re: Lost thrust while at cruise speed

What exactly is spun? How many $$$$$$. How tough to fix? I did not hit anything, but it is possible another in my family "borrowed" my boat. Unconfirmed at this point.

Thanks

 

[chriscraft254]

Re: Lost thrust while at cruise speed

Honestly, you don't have to hit anything for a hub to get spun. They can just wear out. I spun one without hitting a thing. Does sound like you spun the prop though. Spining the prop/ hub means the hub has spun on the shaft splines. Basically the prop shaft is turning and the hub/prop assembly isn't.. Most the time, you can still idel in but can't get on a plane. The hub assembly is designed to break when you hit something so you don't cause other significant damage to the lower unit.

 

[Bridar]

Re: Lost thrust while at cruise speed

If you have a spare prop, give it a try and inspect the splines on the prop shaft while you change props. If your drive still slips after changing props, you may have a blown gearset. Let's hope its just the prop hub.

 

[krudville]

Re: Lost thrust while at cruise speed

Just got the boat out from storage, same issue. the prop is not spun. What is a blown gearset? cost to repair? Evidence points to someone coming in to the dock fast and probably hitting reverse hard. THere are marks on the front of the boat and a broken board on our dock. What damage can occur when hitting reverse hard? I don't hear any bad noise, and no smells, just revs up. Very consistent. Any ideas? Thanks.

 

[Bridar]

Re: Lost thrust while at cruise speed

Okay, if the prop is not blown, that narrows it down to the upper or lower gearset, the clutch dogs or engine coupler. You can easily remove the top cover on the upper gearcase by removing 4 bolts to inspect the upper gearset. Here is a pic of a healthy gearset.
These must be imersed in gear oil while running or it will soon suffer a catastrophic failure at WOT, as shown in the next pic. The proper oil level will be just above the horizontal input shaft.
. Checking the lower gearset and clutch dogs will take more time, but tell-tale signs are metallic particles in the lower gearcase oil and slack between the prop shaft and the vertical shaft in either forward or reverse. To check the engine coupler, unbolt & pull the outdrive from the transom and check the splines on the input shaft & engine coupler. Do you have a service manual?

 

[Maclin]

Re: Lost thrust while at cruise speed

How are you so sure about the prop? Did you try another one? Hitting reverse hard at higher forward speeds will stress the prop-to-hub relationship.

 

[Don S]

Re: Lost thrust while at cruise speed

If it runs ok at low rpm and speed, then the gears in the drive are not your problem. How did you check your prop? What you need to do is mark the center hub of the prop, take if for a run and make it slip. Then see if the lines are still lined up or not. If the lines are lined up, then the coupler is probably spun. UNLESS, you have a cone clutch drive. Post a picture of your outdrive, or post the numbers on the tag on the port side of the drive behind the trim cylinders.

 

[krudville]

Re: Lost thrust while at cruise speed

I marked the prop. Took it for a short run. It got up to mid-speed and then revved up. The marks are still aligned.

 

[krudville]

Re: Lost thrust while at cruise speed

Thanks for the reply. Probably above my technical ability. I do not have a service manual either. I'm going to get another prop and try it. it feels tight when shifting forward and reverse the only problem I have is when I go to throttle up it just revs up and loses thrust.

 

[krudville]

Re: Lost thrust while at cruise speed

Can a coupler slip like a spun prop? It is strong right up till I try to get on plane. I can repeat over and over, it does it the same every time. I am going to get another prop and try again. I want to be sure thats not it before tearing into the outdrive.

 

[krudville]

Re: Lost thrust while at cruise speed

Hard to read the numbers on the tag but I believe it says 386-8076 I will try to post a picture as well thanks for all the feedback.

 

[krudville]

Re: Lost thrust while at cruise speed

Here is a picture of the outdrive. The numbers on the tag are PROD # 3868076 Type can't read Ratio 1.66 Serial #TO 785281 Thanks all.

 

[Bridar]

Re: Lost thrust while at cruise speed

When it starts revving up at planing speed, does it re-engage when you start to slow down? Or do you have to stop, shift to neutral, back to forward and start again?

 

[krudville]

Re: Lost thrust while at cruise speed

I have always pulled the throttle back quickly to neutral I've never let it go and see if it would reengage. it feels to me like I have to go to neutral and then reengage and it works good every time

 

[Don S]

Re: Lost thrust while at cruise speed

That is the SX model, it has a cone clutch that could be slipping. Check the gear lube and see if there is water in it. You also need to remove the back cover and make sure the shift cable is pushing the shift mechanism all the way into gear. Worn cables won't let it get all the way into gear.