1975 70HP Evinrude Hustler Just Aint Right-Need Guidance

[TexAgDoc]

Howdy All - I really appreciate your help on this one because its been driving me nuts. Backstory here is that I'm new to being a father and currently a veterinary student. Life has been busy. But now I have the summer off and a little more cash in my pocket and I'd like to get this engine problem solved. I'm not really into throwing money at parts so anyway I can "test" something before calling it quits would be preferred.

I've taken it out probably 2 dozen times. It has never once failed to start on me and never once died (maybe occasionally at low throttle when docking - still need to adjust that.)

Pretty consistently, what happens is that it cranks right up (no problem). I let it warm up on the trailer for a good 3-5 minutes. I'm in Texas so its HOT anyway. And then when I take off from the dock and ask for WOT, it probably goes to about half its capable RPM range and just hangs out there (during that time my throttle arm i full forward). Can't get it up on a plane, no nothing.

Anyway, after about 5 min - and sometimes I'll try to wind her up in neutral and turn it off and back on again (doesn't seem to help), there will be like the sound of a hiccup and then instantly she runs like a swiss watch - usually for the entire day. No problems whatsoever... Recently I went out and did this same thing but this time I asked for WOT and it gave me half.... so I was waiting waiting.. then it revved way up but sat dead in the water, then when I backed it and asked for WOT it gave me half again and started to propel me then got up on a plane... Once it has done this I can usually get on and off a plane fairly easily... I just don't get it. I'm at a loss. Any Ideas?

Since I've had this issue I've done new plugs and when I first bought it checked compression (about 1.5 years ago now) and they were all within a couple PSI of each other.

Thanks!

 

[flyingscott]

Check for spark when that happens you can get a spark checker for about $10. It sounds like you might be running on only 1 or 2 cylinders.

 

[TexAgDoc]

Great. I actually have one. I’ll give it a shot tomorrow. Any chance I can just do it in my yard with the cups on it? Seems like the problem goes away and it being under load should not affect whether there is spark or not. Agreed?

 

[TexAgDoc]

So - In the yard I hooked up the cups today and put the spark tester on it and all cylinders had lots of spark being thrown from them. Even put it in gear and ran the throttle up and all cylinders through lots of spark. This thing almost seems mechanical... something slips after a few bumps on the water then everything starts working once again.

To anyone just joining on now to the chat the short of the long is that when I first go to run the boat I ask for WOT and it only gives me half... then there is a hiccup after a few minutes of this and the boat takes off gets up on a plane. Usually for the rest of the trip it doesn't happen again.

I guess my next thing I need to do is take a buddy, do a sea trial and start pulling plug wires when this happens and see if I can isolate a cylinder - or see if mechanically the carbs aren't getting there flappers opened all the way. Again - it seems like when it warms up the problem happens less (although not always).

Its easier for me to test stuff at the house since I'm at home watching my 1.5 year old.

Thanks!

 

[Keyboardman]

Might want to check that your advance/timing base isn't sticking.

 

[jimmbo]

Try the spark test in the water, under load. Are the chokes fully open?

If your engine is a 1975 model, it is either a 70hp, or a 75hp Hustler

 

[fireman57]

Have you tried pushing the key in when it does this for a quick bump of fuel and see if it picks up?

 

[TexAgDoc]

Thanks guys. Yeah sorry about the typo at the top it is indeed a 75HP. What should I be looking for that would tell me that my advance/timing base is sticking? I probably won't get a chance to sea trial until Wednesday of next week. But will keep y'all posted and appreciate the help.

Also-I have bumped the key to make sure chokes aren't sticking - when I cleaned the carbs I tried to make sure they were all fully functional - bumping it after 2-3 min running will generally try and kill the engine.

 

[Keyboardman]

The timing base is under the flywheel. There is a rod that attaches it to the throttle linkage. As you advance the throttle, the timing should go forward all the way to the black stop before the throttle plates start to really open. I had the metal wiring holder stopping it from advancing all the way on my 75hp Stinger.

 

[TexAgDoc]

Update: I went out fishing on Saturday (caught a few bass) with my FIL. Since our discussion on here I have checked spark while on the cups and it looked good. Also I but a brand new fuel pump in. We really went out there to fish but while I had someone else to drive the boat I took the cowl cover off and had him floor it while I played with the engine. I was curious if the timing advance lever was sticking as one poster suggested. But straight out from the dock we were trying to go WOT first thing and the problem where we are asking for full power but only get half happened again. The advance lever was not sticking. Went all the way to the black bumper. So I just pushed it back and forth and the engine dogged down more then when I let it go back to where it wanted to be it was back to its half power when asking for WOT. I was hoping I’d find a hang up there. Anyway. Put the cover back on and just kept on going at that pace for maybe 3 minutes more then ... there was a small skip in the motor and off she went. WOT. ran great for the rest of the day.

Things I’ve noticed when it’s behaving poorly are that it idles really rough. I can have it in idle in neutral but as soon as I put it into gear it either dies or really wants to die. If I catch it just right I can slam into gear and get the rpm up quick enough where I can take off. After the little pop when the motor has just been turned on at the beginning of the day, like when you ask for WOT and it actually gives it to you-I never have that issue again. Idles great and never dies while putting it into gear.

Maybe one other thing I have noticed is that when everything is working right and it does come up to WOT and plane out... it does so kind of slowly and not very smoothly. It’s almost like it’s having to catch up with itself too. Once it’s ripping it’s ripping though. So can’t complain there. But I wouldn’t say it’s rapidly on demand. Maybe that’s another clue. It should push the boat great. It’s only a 1992 16’ fiberglass nitro. I think it’s even over powered for what is called for originally.

HELP

ETA: I know that I still need to check the spark under load when this is happening. So wondering if there is any insight given more info I have provided. Or if anyone is suspecting anything.

 

[racerone]

Does spark jump a gap of 7/16" on the 3 leads, yes or no ?--------What are the compression numbers with a good gauge ?----Have you test run with another tank and hose ?----Inspected the fuel pump diaphragm ?-----tried pumping the manual fuel pump when it acts up ?-----Spark " under load " is something I have never looked at as it means nothing to me.

 

[jimmbo]

I would be checking the floats to see if they are operating properly, no binding or interference from the little clip between the needle and the float. Also looking for signs that dirt might be keeping the floats from closing,

 

[fireman57]

You might try running it with the cover off and see what happens. Might have an exhaust leak. Also, try it with the airbox off so you can see the throttle plates and make sure they are opening all the way. When you are taking off and only getting half the throttle you should have someone close a carb body off with their hand and make sure it is drawing air as strongly as it should. When you had the carbs off did you shine a light back into the reeds and make sure a screw or something else has not been sucked back into them? Has happened more times that I would like to admit.

 

[TexAgDoc]

Does spark jump a gap of 7/16" on the 3 leads, yes or no ?--------What are the compression numbers with a good gauge ?----Have you test run with another tank and hose ?----Inspected the fuel pump diaphragm ?-----tried pumping the manual fuel pump when it acts up ?-----Spark " under load " is something I have never looked at as it means nothing to me.

Going to try my best to respond to all things here the best I can.

1) I have not tried the spark jump of 7/16” yet. Looks like I need a new tool that I’m going to get.

2) As for compression numbers with a harbor freight gauge (had it laying around. I guess I can go rent one from o Reilly’s if you don’t find the following acceptable)

-so I tested today and got:

*125 PSI top, recheck top 120 PSI, re re check 120 PSI, .031 inch gap for spark plug




*135 PSI middle, recheck 135 PSI, .030 inch gap




*135 PSI bottom, recheck 130 PSI, re re check 125 PSI, .033 inch gap

3) I have not tried a new tank yet. Don’t want to buy one but I can if this seems like top of differentials. When I have ran and had the half power problem I have tried opening up the cap... I can’t remember if I have pumped the bulb while running during this issue but when I first start the engine it always pumps up tight right before.

4) fuel pump is brand new as of last week and please read comments above. That is included.

5) I have cleaned the carbs and visually confirmed the float moved freely etc. after I cleaned them it did not change the way it ran at all. I did not replace any carb parts when doing this. Honestly it looked pretty good. Gave the bowls a shake. Didn’t seem like they were holding any fluid

6) earlier up in posts I mentioned I had spark tested it and I thought knew what that was but just recently learned of this 7/16 gap rule. I’m gonna get that tester and report back.

7) I haven’t had a chance to have someone running it while I mess with the engine because it’s my wife holding our young son which doesn’t give me a lot of options. But I will try this soon when I go out with a buddy. Thanks for the suggestion.

8) I did have a moment about a month ago (hardly would idle ever) when I noticed that the carb banks were loose due to loose nuts and that a couple of the flat head screws holding the intake manifold to the carbs had come out and I found one almost going into the engine past the carbs. I’m assuming those are the reeds?!?! I retrieved it and locked all those connections down tight. There was still one screw not accounted for. (Maybe happened during previous owner-a year and a half ago).

***at this point in time I’m wondering if some sort of weak ring in the cylinder may be to blame (since it heats up and maybe things expand and start working more efficiently) or something of that sort since it only runs quite well (with some hesitation in response to throttle but overall it winds up and runs real fast and pushes the boat damn quick) or if as others have pointed out either a) there is a screw that made it past the reeds (don’t know why if this was the case the problem would seemingly resolve itself throughout the day) or b) if the spark jump of 7/16 inch may reveal something - I think in an earlier post I did say that I put a spark tester just to see if there was any spark at all and with the cups on it was showing lots of spark with the flashing light- but I know now I need to use a different tool and will do so soon.

Thanks for the help-I know it’s a lot-posting from a phone sorry for typos

TXAGDOC

 

[TexAgDoc]

Just a little update. And to summarize for those who are confused what the problem is... seems like for the first 10 minutes of the day the engine will not idle. And if I slam into gear and try to take off it sounds all bogged down at WOT. Then there is a hesitation and it just takes off and runs great the rest of the day. Isles great. No problems whatsoever.

I just did the 7/16 spark gap test and it was a strong blue flame on all 3 leads.

Does this put me back to fuel issue?

 

[TexAgDoc]

PROBLEM SOLVED: Brief summary. This is a 1975 75HP Evinrude Hustler. I replaced the fuel line and bulb and the problem is gone. Wish I would have kept it simple.

Problem: Loss of power at full throttle intermittently, rough idle at times - sometimes it would run great for hours.

Discussion: I really felt like since this problem came and went that it was something else. Carbs maybe? I must have cleaned 3 times and rebuilt, new fuel pump, new carb fuel lines...When I inspected the fuel line with the pump from the gas tank it sucked up gas and spit it out, it was older though (not sure how old). So it appeared to work fine... replaced it with a generic one off of Amazon. Did the trick.