Johnson 70 HP - No power when under load

[jughead0691]

Hi all. I am brand new to boating and currently experiencing a problem with my Johnson 70 HP. I purchased the boat 6 days ago and was advised from the gentleman that I bought it off that the boat performed well the last time he used it (Eight months ago). I took the boat out for the first time today and found that the engine stalls and when it actually runs when it is in gear it is extremely low on power. It will not rev at all. I am a mechanic by trade but outboards & two strokes are new to me. It seemed like the ignition timing is out of adjustment. Or maybe it my be the carbs?? I have checked all the spark plugs, leads, fuel filter and replace the fuel with a fresh tank. Can anyone please help me with this?? Suggestions would be appreicated.

Cheers,

Paul

 

[tashasdaddy]

Re: Johnson 70 HP - No power when under load

what year or model #??? i suggest checking compression, should be over 100 psi, but more important the readings are within 10 % of each other. timing and carb cleaning are cover in the following link. without model # i cannot tell you the timing setting.

http://forums.iboats.com/showthread.php?t=299680

 

[RJDAWSON]

Re: Johnson 70 HP - No power when under load

I hate to sound like a broken record, a quick look at the stator for driping resin or sticky to the touch might show you the problem. An ohms test of the stator is quick and easy, just need a year for your motor... from 76 -90 most resistance readings are between 0.8-1.4, please check your manual. If you don't have the specfic for your motor, check out E-bay also Johnson/Evinrude will be the same.

 

[jughead0691]

Re: Johnson 70 HP - No power when under load

THanks guys. I think it is a 1984 model - there is no year date on the tag. The model number is J70TLCRD. IS this the info you guys need?? Thank you.Cheer, Paul.

 

[jughead0691]

Re: Johnson 70 HP - No power when under load

Hi guys me again, just check the compression 110 psi in all cylinders. I removed the fuel pump diaphram to find it cracked. I am going to replace the fuel pump and re-kit the carbs. I checked the stator and it is not dripping. Looks good. Thanks for your help. Really appreciate it.

Cheers,

Paul.

 

[chucko]

Re: Johnson 70 HP - No power when under load

Youve located the problem. Dont go throwing money away on carb overhauls, as its a lengthy unnecessary thing to do at this point. Get the pump going, and likely your problem will be solved. Good luck.

 

[rickdb1boat]

Re: Johnson 70 HP - No power when under load

I think it would be wise to go ahead and rebuild/clean the carbs since this is a new purchase and it's hard to tell when it was last done. Considering how long the engine has sat unused (8 months) is enough to warrant the rebuild. Only takes one clogged carb high speed orifice to toast a cylinder. Plus with the new kits, you know that you will have ethanol resistant parts in the carbs..

 

[HybridMX6]

Re: Johnson 70 HP - No power when under load

I agree with rickdb1boat, seeing as how it set for the past 8 months, and who knows when it was done last, I'd do the carbs. I'd probably even do the water pump while the carbs are off since it is a lot easier to disconnect the shift linkage with the carbs out the way. $200 in parts and a few hours of your time are well worth saving a possible $1500+ repair job b/c a high speed jet was clogged and fried a cylinder, or the impeller was toast and overheated the engine.

 

[JDs Dorsett]

Re: Johnson 70 HP - No power when under load

Hello, I just posted something similar, same motor, kind of same problem, will not go faster when throttle is pushed full, stays at a slow speed. I had a mechanic look at it and he too thought it was something with the advance. he adjusted it and thought that someone just did it wrong, and it should now be ok. but it wasn't, same problem. maybe this is a problem with these motors, maybe someone out there can help us. your half way there as you are at least a mechanic with better knowledge to understand the tec. stuff,good luck, I just got this boat and motor too. very frustrating to see it sit at dry storage.

 

[.Bennett]

Re: Johnson 70 HP - No power when under load

I think it would be wise to go ahead and rebuild/clean the carbs since this is a new purchase and it's hard to tell when it was last done. Considering how long the engine has sat unused (8 months) is enough to warrant the rebuild. Only takes one clogged carb high speed orifice to toast a cylinder. Plus with the new kits, you know that you will have ethanol resistant parts in the carbs..

This. Completely worth the time, effort and money. And ethanol resistant is a must. That stuff is murder!

 

[jughead0691]

Re: Johnson 70 HP - No power when under load

Thanks for all of your replies. I decided to go ahead and remove and strip the carbs. I found that the No.1 & No.2 carb bone dry and both needle and seats stuck closed. No.3 carb float bowl was full and the needle and seat working. I will rebuild them when the kits arrive. Does anyone know where I can get a exploded diagram of a carb? Thanks again. Much appreicated.

Cheers,

Paul.

 

[HybridMX6]

Re: Johnson 70 HP - No power when under load

should be able to get one online at shop.evinrude.com, and follow the prompts for partsm then select your engine brand, year, hp, and specific model #.
You should look into a factory manual for that engine, they can be found online an kencook.com I believe or on ebay. Ebay it hit or miss though, but if you find one, it will be a lot cheaper.

 

[jughead0691]

Re: Johnson 70 HP - No power when under load

Update - tested the boat in the river this afternoon. FAULT STILL THERE. There is not difference. Still has now power and stalls when selecting gear. Will not run in gear. Has anyone got any other ideas?? Cheers Paul

 

[tedious]

Re: Johnson 70 HP - No power when under load

Is that after you rebuilt the carbs? And you put a new diaphragm in the fuel pump, right? Then the next thing I would check is the link and sync - sounds like the carbs may be opening up before the timing is advanced far enough. DO NOT mess with the timing itself at this point - hard to see how that could go bad in 8 months of sitting idle.

Get yourself a factory manual if you don't have one - it should describe the link and sync procedure.

Also, what do the plugs look like after a run?

Tim

 

[jughead0691]

Re: Johnson 70 HP - No power when under load

Yes that was after the carb rebuilds and fuel pump re-kit. I will check the plugs. Thank you for your help. Much appreicated.I will track a manual down ASAP. Many thanks Paul.

 

[tedious]

Re: Johnson 70 HP - No power when under load

Paul, I think you can get a downloadable copy of the manual (for a fee, of course) from www.marineengine.com - might be quicker than waiting on the slow boat from whereever.

Tim

 

[jughead0691]

Re: Johnson 70 HP - No power when under load

Thanks Tim. You have been a great help. Cheers Paul.

 

[WIMUSKY]

Re: Johnson 70 HP - No power when under load

Considering how long the engine has sat unused (8 months) is enough to warrant the rebuild.

Man if that's the case, some of us boys in the northwoods would have to rebuild carbs every year. We can have ice on the lakes for 6 months.....

 

[RJDAWSON]

Re: Johnson 70 HP - No power when under load

Did you do an ohms test on the stator?
I found that the rubber conecters are sometimes hard to put back together, I've been using a dry teflon spray lube( get it at the auto store) to help recouple the conecters after the test.

 

[jughead0691]

Re: Johnson 70 HP - No power when under load

ANOTHER UPDATE - I got the motor running now. I remove all carbs and re-adjusted float levels. Refitted and found the ignition timing adjustment. Changed the timing and started first attempt. Boat performs excellent with plenty of power. I just need to fine tune it a little more. Can anyone tell me what the timing setting is and what the procedure is to do it? Once again thanks very much for all of your help.

Cheers,

Paul