1974 Evinrude -50 HP Model 50473 M loss of power while in water

[mstone1968]

Hello Everyone,<br />I'm fairly new at the boating world and engine maintenance, so please forgive me if I ask a dumb question. I just bought a boat with a 1974 Evinrude 50 HP motor - model 50473-M. The boat is a 1974 starcraft 15 foot fiberglass boat. The motor starts right up and runs smoothly while idling. When you move the throttle all the way forward, the boat never planes out and takes off, it just kind of raises out of the water in the front and continues to run that way down the lake. If I run it out of the water with water muffs the motor sounds like it has plenty of power but when it is actually in the water it only sounds and feels like it is running at half throttle. I installed new spark plugs and adjusted the idle speed up a little because it kept wanting to die out when I put it in gear. The idling is running smoothly now, just not getting much power out of the motor when I push the throttle down. Would anyone happen to have any suggestions on what to check. The engine sounds smooth - no missing or anything like that, just no power. Thank you so much for your time and patience.<br />Mike

 

[tashasdaddy]

Re: 1974 Evinrude -50 HP Model 50473 M loss of power while in water

is it possible your hull is waterlogged. borrow a compression tester and record compression. from the back of the engine on the left side follow the fuel hose to a black square w/ a screw in the middle. this is a fuel screen. unscrew, and check for debrie blocking fuel flow. im sure the others will come along and add a lot more to this. welcome to iboats.

 

[WillyBWright]

Re: 1974 Evinrude -50 HP Model 50473 M loss of power while in water

How are the sparkplugs burning? Both firing? A non-firing plug will stay clean. Make sure the timing is advancing and the throttle butterflies are fully opening. You could also have a blown head gasket if water is getting on one of the sparkplugs. It sounds to me like you're running on 1 cylinder.

 

[mstone1968]

Re: 1974 Evinrude -50 HP Model 50473 M loss of power while in water

Hello tashasdaddy and WillyBWright. Thank you so much for responding. I will try your suggestions today and will post the results.

 

[mstone1968]

Re: 1974 Evinrude -50 HP Model 50473 M loss of power while in water

Hello guys, I really appreciate your help so far and thank you so much for your time.<br /> <br />Here are my results so far:<br />. I took the fuel screen off and cleaned it. It did have a little bit of debris on it so hopefully this will help with overall better fuel flow.<br /><br />. I don't think the hull is waterlogged. It seems to be in really good shape, no scratches or holes. It moves fine through the water with a trolling motor? It looks like the boat has been well taken care of?<br /><br />. I haven't found anyone with a compression tester yet. I may have to take it into a marine shop to do that. <br /><br />. I put new spark plugs in and when I took them out they had oil on them. So hopefully both cyliders are firing? If one isn't firing will there still be oil on them? I didn't see any water on the spark plugs.<br /><br />.When I move the throttle forward or reverse, there seems to be a lot of play in it before it actually takes off. ( I would say it goes about 1/2 the distance between neutral and full throttle before going into gear) Is this normal or should it go into gear sooner. It seems to me that it isn't getting the full amount of throttle.<br /><br />.From the back of the engine on the right side, the two brass rods with the black plastic rings that move when you move the throttle - it seems that adjusting these increase and decrease the amount of gas. Would you mind to tell me what the top one and the bottom one do exactly. It seems the top one affects the idling speed and the bottom one affects the throttle speed? I tried adjusting these while the motor was running and it did seem to increase the throttle, but then it wouldn't start until I adjusted them back. Is there a procedure to follow that will let me adjust these properly? When I adjusted these, the warm up lever doesnt work now, If I put it in gear it automatically moves the warm up lever down and when I move into neutral the warm up lever moves up, but it is not independent like it was before. All I done was rotate the black plastic rings on the brass rod. But the lever doesn't work now. Moving it doesn't affect the Idle speed like it did before?<br /><br />Like I said I am very new to this. I know I may sound stupid on some of this but I do enjoy working on stuff like this. I just want to do it correctly. Thanks again for your time tashasdaddy and WillyBWright. Have a great day. Hope to hear from you soon.<br />Mike

 

[rstreckjr]

Re: 1974 Evinrude -50 HP Model 50473 M loss of power while in water

hey I have a 1978 140 rude and mine was doing what you originally described throttle controls were at full with no power, couldn't even make plane. my fix to my problem was the prop hub bushings were dry rotted, take your prop off and look at the rubber on the back side of the prop the rubber you see in there will tell you a story, of wether or not to get it replaced. Hey, $42 DLS later, I went from 8 mph to 45 mph.

 

[mstone1968]

Re: 1974 Evinrude -50 HP Model 50473 M loss of power while in water

Thanks rstreckjr for the information, I will definitely check that out in the morning. I will post my finidings. Thanks again,<br />Mike