1973 EVINRUDE 135 HP - gradually loosing speed on the water

[BagOFchips3071]

i have a 18ft ski boat with a 135 evinrude (1973) outboard, took it out last weekend and it never quite seemed to have the power it should have from the start.....seemed to be about half of what it should be....and then the longer we ran it....the boat would gradually go slower and slower, even though the motor sounded fine and was at almost full throttle the whole time. never moved the throttle down....yet speed gradually decreased.
barely made it back to the dock, going very slow (at full throttle) by the time we got back.

any ideas?

Thanks,
Josh

 

[ezeke]

Re: 1973 EVINRUDE 135 HP - gradually loosing speed on the water

Sounds like your prop is going [spun]. Mark the hub sections and run it again. If they don't stay aligned, you will need to take it to a prop shop.

[Edit] Actually, after that much running, you should be able to easily see the damage to the grommet. Just take the prop off and look at the hub from the back.​

 

[CATransplant]

Re: 1973 EVINRUDE 135 HP - gradually loosing speed on the water

A spun hub is one very, very good reason to carry a spare prop in your boat. It can happen anytime, and that spare prop will prevent a lost day on the water. There's a place somewhere on the boat to stow a spare prop, prop nut, wrench and any other item needed to mount the replacement. Wraw the whole kit in an old towel and you'll be the hero of the day if you spin your hub.

 

[BagOFchips3071]

Re: 1973 EVINRUDE 135 HP - gradually loosing speed on the water

EZEKE, you were absolutely right! it was so obvious just looking at it...didnt even have to mark it and run it. the rubber was comletely separated from the shaft on almost half of its circumference.
Also, I think I may know how this happened. I was talking to a buddy about this problem and he said that according to his manual, when I run the motor on the flush kit and water hose, that I should make sure not to rev it too high since its not under a load it could cause problems. I never knew not to do this and have reved a little high sometimes because the motor dies easy at idle...so i would keep it reved to not let it die. it did not used to have trouble idling until I had lost the key and had to remove the ignition switch from the throttle box to take it to have a key made for it at the locksmith's. I think when i reassembled the throttle box, I set the idler lever (on the side of the throttle box) too low.
Do you think this is what led to the spun prop?
If so, would it be ok to rev it on the flush kit as long as i remove the prop before i run it? or could that still cause other problems?
Also, is there a way to adjust the idle at the motor rather than trying to adjust the lever in the throttle box..or should i just try to put the idler lever back the way it was originally?

Many Thanks,
Josh

 

[mitchell6]

Re: 1973 EVINRUDE 135 HP - gradually loosing speed on the water

Don't rev your engine at all on the muffs I don't let mine get over 1100 rpm's had the same engine as you till last year and I did the same thing not knowing better of course a few weeks later I was replaceing the powerhead cause it broke a ring don't know if it was from reving it on the muff's or not but you can bet if that's what it was it want happen again

 

[ezeke]

Re: 1973 EVINRUDE 135 HP - gradually loosing speed on the water

The prop problem is just age and the heat from the exhaust unless you hit something with the propeller. Get the prop fixed and get out on the water.

No matter what, keep the running and the RPM to an absolute minimum whenever you have no load on the system - good for flushing and not much else.

I'm sorry you lost a good ride.

Tight Lines.​

 

[hoeser]

Re: 1973 EVINRUDE 135 HP - gradually loosing speed on the water

Revving the engine on the muffs would not have caused this prop failure, you really shouldn't rev on the muffs though as there is no back pressure on the exhaust system.

IF your engine hard to keep running at idle, you may want to figure out what is causing that