1977 70hp evenrude starts fine but dies when throttling up.

[roonie]

Just bought this boat (1977 lund fiberglass dart 14ft.) with a 1977 70 hp rude. She starts just fine. I warmed her up and as i begin to throttle her up she dies almost every time. The only time it will take off is when i creep the throttle up ever so slowly and even then i have trouble. The fellow i bought the vessel from stated that he had the carbs done the year previous. I should add that of the few times i have been able to keep her running and WOT she just flies (38mph) and seems to run fine. I was told the tank cap must be half open to allow for air and in fact found out the hard way the other day when left the dock. Could it be that opening the tank lid halfway is still not enough air for the tank? Also....the seller told me it had a "dead spot" when pulling skiers etc. but his boat mechanic told him he bought the problem when he bought this engine. ????
I did a comp. test tonight and found the three cylinders to be only 55 lbs. exactly each hole. Aslo...it took 8 pumps to fill the bulb...is this normal? Any help would be greatly appreciated. Just love the website here by the way. Searched but could not find a similar thread.

 

[roonie]

Re: 1977 70hp evenrude starts fine but dies when throttling up.

im bumping this up as I need help soon

 

[Daviet]

Re: 1977 70hp evenrude starts fine but dies when throttling up.

The compression is way low, might try checking it with a little oil in the cylinders and see if it comes up. Since the engine runs maybe do a good decarb and see it comes up. You might think about pulling the head and see if there is any cylindr or piston damage.

 

[Sixmark]

Re: 1977 70hp evenrude starts fine but dies when throttling up.

Might want to redo the compression test with a different gauge as well, 55psi seems awfully low for a motor that is "getting up and flying".

 

[emoney]

Re: 1977 70hp evenrude starts fine but dies when throttling up.

It's been said, but I'll echo the "redo" on the compression test. I've never counted the # of times it takes to fill my fuel bulb, but on the surface that seems like a lot, however, if you're able to pump it and it remains firm, then I wouldn't think that's a biggie. But, if it requires you to be continually pumping the fuel bulb then it sounds like there's a leak in the system somewhere. First thing I'd do, though, is open the the fuel cap vent all the way and see if that rectifies your issue. Depending on the how the cap's made, 1/2 way may not be actually opening it.

 

[Bamaman1]

Re: 1977 70hp evenrude starts fine but dies when throttling up.

Suggestions to start:

1. Pull the siphon on your gas tank and see if there are any blockages on the bottom of the tube. Sometimes there are filters there.
2. Check the engine for fuel filters--and change them.
3. Does the cap on the gas tank has a vent, and is it letting air in?
4. Go to WalMart and replace the fuel line and bulb with a universal kit. (I always like to keep one as a spare anyway.)
5. Get new spark plugs and install them.
6. Inspect the carbs. After motor runs, are there any drips in the throats of the carbs after the engine is shut off? That would indicate sticking needle valves in the fuel bowls--and cause you to bog down on acceleration.
7. Pull the carbs, disassemble, clean them with a can of carb cleaner and reassemble. Be careful disassembling the carbs, and you can reuse the gaskets. Also note how many turns out any adjustment screws are--and reset them the same. (Carb cleaning is a simple job--not rocket science--and 2 strokes don't require any carb kit.)
8. Is your boat running right now? If not, warm it up and then check your compression on the cylinders.

All in all, you might spend $25 and 3 hours time doing these normal maintenance items. Another thing I'd suggest on any "new" used boat is always change the water pump impeller and inspect/change the lower unit oil before you use it.

 

[roonie]

Re: 1977 70hp evenrude starts fine but dies when throttling up.

thanks for the quick response...i really appreciate it.
The fuel tanks are metal older but in almost perfect cond. The lids have no vents just the half turn and full turn lids.
I used a push/pressure comp. tester and i fully agree that it should be redone with a better comp. tester. I agree...it flys too fast to be that poor of an engine.
The carbs were redone only a yr. ago
The bulb and hose look real new..but i will call the previous owner and ask a few more questions.
The spark plugs were just changed but ngk and not the plug the engine sticker calls for...does this matter?
One thing i know needs changing is the impeller as the previous owner has had this since new and claims the impeller has never been changed....yikes!
One thing i would like to have an answer to is.....this engine has zip ties all over every gas line in the engine etc. Are zip ties ok to use rather than a clamp style?
Is it worth pulling the flywheel and cleaning/changing the points and timing the engine?
also....where does the water pee out....i did not see any? I read about the tell tale retrofit but shouldnt there be a pee come out somewhere on the engine down low from factory? Sorry for all the questions fellows

 

[Daviet]

Re: 1977 70hp evenrude starts fine but dies when throttling up.

Replace the pump, not your running problem but sounds like it needs to be done. Install proper plugs. Zip ties are used on fuel lines, I have a tool that gets them to the proper tension. There are special ties for gas lines, but I have seen regular ones used with success.

 

[roonie]

Re: 1977 70hp evenrude starts fine but dies when throttling up.

and the pee comes out ...where on this engine?

 

[patrick4266]

Re: 1977 70hp evenrude starts fine but dies when throttling up.

Take out all the plugs when doing the comp test, go to auto zone and rent you a good gage, Your numbers are wrong big time. Get you a rebuild kit for all 3 carbs, link and sync, impeller change and you will have a good motor. You need to throw a few bucks into it, but not a whole lot.

 

[Daviet]

Re: 1977 70hp evenrude starts fine but dies when throttling up.

According to the parts breakdown, you don't have a tell-tale. You can install one, do a search, there are several posts on how to do it.

 

[roonie]

Re: 1977 70hp evenrude starts fine but dies when throttling up.

patrick4266...my first post states the carbs were done last yr. why do them again?
Is there a step by step on this site that im not finding on how to change an impeller rather than getting a manual?

 

[Daviet]

Re: 1977 70hp evenrude starts fine but dies when throttling up.

Get the factory manual, it will be the best money you have ever spent.
I don't know of a site that has step by step instructions, but you tube has some repair videos posted, maybe try there.