evinrude 70hp 1975 lost allot of power

[firstimer]

i have a 1975 envinrude 70hp engine. The boat sat for a while. I rebuilt carbs and got it running. I took the boat out today and had it running good for about ten minutes. I then proceeded to put it full throtle. It ran great for about a hundred yards then lost most of the power. I let it idle for a little bit tried again but no power. It moves but only about ten mph. Also i have been running the boat off the hose out the water. I was also wondering is water supose to come out of the two holes located near the head off the engine. The two hole are next to each other about an inch or two apart. I was thinking that maybee the water pump was not working because i never saw water come out of them. All i ever saw was a tiny bit of fumes. What did i do? thanks for the great help once again. I am enjoying learning about boat engines and my mistakes.<br /><br />Brad

 

[mikeyzx2]

Re: evinrude 70hp 1975 lost allot of power

sounds like it's overheating. if you're talking about the two ports on the rear on the exhaust housing then they are supposed to have waterspray coming from them. I would say to check the heads to see if they are getting too hot to touch but that would risk damaging the engine. best bet is to replace the impeller and thermostat to be safe. stat could be stuck closed and/or the impeller is shot

 

[firstimer]

Re: evinrude 70hp 1975 lost allot of power

i am new at this and was wondering what the impeller is? what does it do? where would i find it? Is it the same thing as the water pump? Since i cant get the power i first was do you think i already damaged the heads?<br /><br />Thanks for all the great input!<br />Brad

 

[Boilermaker]

Re: evinrude 70hp 1975 lost allot of power

I am far from being an expert, and their are many here that ARE EXPERTS>>>but first things first. It sounds to me like you lost power from one or 2 cylinders.<br />First off, do a compression test.<br />Hook up your hose & "ears" and run water before starting the engine (just a few seconds of dry running will wipe out your waterpumps impeller>>the part that pumps the water).just run it for a few mins. to warm the cylinders,pistons & rings.Check the compression of each cylinder and see if they are close to the same pressure. NOTE THE PRESSURE OF EACH CYLINDER. <br />When you pull the spark plugs for the compression test, note the condition of each plug>>>the color,>Black whitish/gray, tan????>>> Is it wet, oily, dry & sooty??? <br />POST YOUR FINDINGS!!! <br />These are the basic, starting points of trouble shooting. By the time you post again, I'm sure one of the extremly knowledgable wrenches here will be able to help you!<br />GOOD LUCK!<br />

 

[firstimer]

Re: evinrude 70hp 1975 lost allot of power

i am sorry if i am being annoying and asking dumb questions but how do i check the compression? What tools do i need? <br />Thanks again <br />brad

 

[MGuckin]

Re: evinrude 70hp 1975 lost allot of power

Only dumb question that exists is those not asked.<br />First investment is a manual. Library will have it if you can't afford it but it will be well worth the investment.<br />Impellors are very simple to change and inexpensive. Make sure the rubber hose connected to the pee hole (for visual reference only) is clear, bugs love to nest in them.<br />Thermostats can be functionally tested.<br />Get your water flowing before doing any other tests.<br />Compression tester can be obtained at any auto parts store.

 

[Boilermaker]

Re: evinrude 70hp 1975 lost allot of power

You will need a Spark Plug Socket wrench(I believe yours takes a 13/16" socket) & ratchet. You will also need a compression gauge, as was stated you can get those in any Auto Parts store, or Sears ect...<br /><br />Warm up the engine on the earmuffs as stated in my earlier post, then shut the engine (and then the water)and pull the spark plugs. Ground the plug wires to the engine block, open the throttle plates on the carbs,insert the compression gauge into the top cylinder, keep everything clear of the flywheel & crank the engine over a few revolutions with the starter>>>Read the gauge & make note of the pressure>>>>move to the next cylinder & repeat.<br /><br />I agree that you should get a manual for your engine>>>but I would do the compression test first>>>their is no sence in spending $30 on a manual if the engine is toast!(unless you are going to do a complete rebuild, or buy the same engine to replace it) & the compression test will tell alot.<br />Good Luck!!!

 

[firstimer]

Re: evinrude 70hp 1975 lost allot of power

eairler i was talking about the impeler and water pump. I have all of the pee holes urinating water. I also talked about the top two holes closer to the engine and i asked are they supose to have water come from them. The answer was yes. I started up the engine and it was working great. I gave it some gas and the engine was hitting full throtle like it was earlier on the lake yesterday. I checked to see if water was coming out of those and there was. It was spiiting out and drooling water. How much water is supose to come ut of those two holes?<br /> Also i am going to the auto part store now to get the compression gauge. <br />thanks again <br /><br />brad

 

[sly36]

Re: evinrude 70hp 1975 lost allot of power

and this 2 holes you supose to have juste spray water exit and i have the same probleme before and i find that is the points adjustement are not good if you are not familar with this engine find the manuel book ist the best think you can do to troubleshouting

 

[Cricket Too]

Re: evinrude 70hp 1975 lost allot of power

It's a lot easier for an engine to hit that full throttle rpm with no load on it on the muffs, but don't keep doing that, it's not recomended to rev an engine that high on the muffs with no load. Are you sure it is running on all cylinders, check to see if you are getting good spark on all the cylinders.

 

[firstimer]

Re: evinrude 70hp 1975 lost allot of power

alright, i tested all of the heads and they ranged all at 105. I hope this is good!! Also, still concerned about the two water exit holes drooling water. are they supose to shoot?

 

[sly36]

Re: evinrude 70hp 1975 lost allot of power

no juste stream spray 105 its goods look for the point set timming!

 

[firstimer]

Re: evinrude 70hp 1975 lost allot of power

so do you think it is ready to go out on lake and give it another try? One thing i also did notice is when i took off spark plugs they were a loose.<br /><br />they where just hand tightened (forgot to tighten Could this have caused everything? <br />All off you are great for the help!!!<br /><br />brad

 

[firstimer]

Re: evinrude 70hp 1975 lost allot of power

forgot to mention the spark plugs are damp with black substance. Looked like oil. they arent dripping but they are not dry.

 

[fireman57]

Re: evinrude 70hp 1975 lost allot of power

If your plugs were loose you will lose power as they cannot ignite your fuel properly for combustion. When you are out running it take a good friend and a pair of well insulated pliers with you and when it starts bogging pull one plug wire. If your rpms change then you are getting spark to that cylinder. Replace that wire and go to the next. Keep doing this for all cylinders. If your rpms do not change then that is the cylinder that is getting not fire. Do this and post back and we will go from there.

 

[Boilermaker]

Re: evinrude 70hp 1975 lost allot of power

First timer>>>In your original post you mention that you rebuilt the carbs...<br />Did you do the work, or a shop???<br />If you did it, did you soak 7 blow out the jets & passage ways in the carbs??? Just wondering if you may have a clogged carb. You did say that all the plugs look similar,"...forgot to mention the spark plugs are damp with black substance. Looked like oil" so it sounds like your not leaning out on one or more cylinders.<br /><br />SOUNDS MORE LIKE AN OVERHEATING PROBLEM as mikeyzx2 first suggested.<br /><br />It is now time to get an engine manual for your 'Rude. You can get one here at IBOATS, at the top of the page.

 

[firstimer]

Re: evinrude 70hp 1975 lost allot of power

boilermaker,<br />i did do the work myself. All of the bowls where clogged with old corroded gas since it did sat so long. I did use carb cleaner to soak them. I did not blow out the carbs but i am positive they are not cloged because i did go back and make sure gas was going throw all of them. I did this by pouring gas in all of the chambers of the carbs and making sure they fill up then opened up all the other ends and watched the gas pour out. What should the sparks plugs look like? I am going to clean them off before we take out on lake in next few days when this rain clears up in knoxville. Then i will check to see what they look like again. I am also thinking they could be oily because when I first tried to get to run i used starting fluid to get the engine started<------ which i later found out is a bad thing to do. you said"...<br />so it sounds like your not leaning out on one or more cylinders." Can you explain because i do not know what that means. What could so of the reasons be that the engine would be overheating?<br /><br />Thanks you so much again and again,<br />brad

 

[michligj]

Re: evinrude 70hp 1975 lost allot of power

firsttimer<br /><br />I'm no expert, but here goes...<br /><br />I have a '74 70hp - very similar motor to yours. Most of the water exits through the prop with the exhaust. you will see some water coming from the two holes just below the cowling at the rear of the motor, but not a strong spray. Since the motor has sat for a while, change the water pump and the thermostats. Buy a manual, it is well worth the 30 buck for how much you can learn.<br /><br />you stated that you did not blow compressed air through the carbs. You need to do this. It doesn't take much to clog a jet.<br /><br />I'm gonna mention a few simply but often overlooked things:<br />1. is the vent on the fuel tank open?<br />2. check the hoses from the fuel pump to the carbs for cracks or looseness. If these are sucking air it can cause trouble. This would cause your engine to run lean (too much air, not enough fuel). from you description of the plugs, i don't think you are running lean.<br />3. check your choke to make sure that the butterflies are all the way open - horizontal. if they are not adjust the choke linkages. This would cause you to run rich (too much fuel, not enough air) and possibly wet foul the plugs. you said the plugs were wet, but I cant be sure how wet<br /><br />after checking these things, when the boat loses power again perform the spark check as stated above by fireman<br /><br />You want to try to isolate this problem as either fuel related or spark related.<br /><br />Right now my gut says fuel, but I could be wrong. If it is a spark problem, it could be an electrical component failing under heat or any number of things.<br /><br />Good luck and keep us posted

 

[Boilermaker]

Re: evinrude 70hp 1975 lost allot of power

Yea>>>I thought FUEL PROBLEM TOO... <br />As far as how the plugs should look, as with most things...IT DEPENDS! If the plugs are brand new, and you run the engine full throttle under load & shut the engine off without idleing, they will be a tan color with a slight bit of oily residue. If they are run a bit & you idle for a long time back to the ramp/dock>>>they will look a bit black & oilly. (by the way...you should also read plug color down the insulator, so you need to shine a light down into the projected insulator to get an accurate reading).<br /><br />What plugs are you running??? How old are they???Are you using a built in fuel tank??? If so, remove the pick-up tube & check it...most have screens on them & it could be clogged. Whats the fuel line squeeze bulb like when you loose power...is it collapsed, has it gotten soft??? Do you have an inline filter between the tank & engine?? As was suggested before>>>how is your tank vent & vent line??? If the vent line sags in the middle, fuel can become trapped there & it can't vent air. How is the fuel in the tank??? Did it sit for a few years??? Do you have a small fuel tank you can try with 100% fresh fuel & oil???<br /><br /> I still have to agree that you should now get the manual & change the waterpump & thermostats. At least, if nothing else, it will give you the knowledge that it is done & the cooling system is good.<br />GOOD LUCK & KEEP POSTING!<br />

 

[firstimer]

Re: evinrude 70hp 1975 lost allot of power

i am going to order the parts from the website. How do i know which ones?<br />thanks<br /> brad