Strange Problem/need Help

[JDs Dorsett]

Hello,I am new to this posting thing but thought I would give it a try. I am not a mechanic and only have basic Ideas of what to try. so here it is, I bought this 17 ft. Dorsett with a 70s Evinrude outboard recently from a guy that told me he had the same problem and was unable to figure out, {he is not a mechanic either}the engine runs fine, and it moves the boat fine under normal harbor speed, {5 mph} yet when you try and give it more gas to get the boat moving faster, it does not push the boat, even with full throttle. it just stays at a slow speed, and even seems as if it will die. The real strange part,......at the dock the engine starts, Idles, and goes into gear fine. but when it is tied to the dock and you put it in gear and give it gas from the motor manually, it acts like it will rip off the cleats from the dock, so it has thrust and power, and when you look at the mechanical action of the shifter for throttle it appears to be functioning as it should. I am at a loss for figuring this out. the only other thing I can think to do is take the throttle cable out and see if it has a break in it, but it seems to be pushing the throttle fine. any Idea would much be appreciated, thank you in advance. John

 

[oldrudedude]

Re: Strange Problem/need Help

What method are you using to manually give it gas at the dock? What lever are you manually activating? Are you manually activating the throttle butterflies without advancing the timing. Pretty hard to advance the throttle and timing at the motor without disconnecting the cable.

 

[Elbo]

Re: Strange Problem/need Help

It won't take fuel or can't get fuel.If it won't take gas the high speed jets are clogged.If it can't get fuel, the fuel pump is not delivering.There is a host of things to check.My sugestion,If you have never worked on one of these or have no idea how it works take it to a boat shop.May be cheaper.If you want to fix it ur self,lets go.Pull the hose off the positive side of the fuel pump,spin the motor and see if fuel comes out.Hold your finger or the pump nipple and see if it builds pressure,should spray out from under ur finger.Moderate pressure.

 

[JDs Dorsett]

Re: Strange Problem/need Help

Hi, and thanks for responding, I know I am going to get schooled from everyone that knows what I don't, so thank you guys but be gentle.
first let me answer your first question. with the motor cover off there is some linkage that you can raise to increase the gas with the motor running, this is what I lifted to see and hear any change, as I mentioned it functions this way as well as when it is in gear, and tied to the dock, it pushes the boat with great force. the lever I was talking about, was the shift lever for engaging into forward gear, { control by the steering} A boat mechanic came down to the dock and tried this and said everything seemed to be working properly, and to go try it out, so I did, and it just would not go any faster. my first thoughts were it was a fuel pump problem, but with all the gas it was getting and delivering at the dock, it seemed fine.

 

[JDs Dorsett]

Re: Strange Problem/need Help

well maybe I am nuts but, how could the jets be clogged if it runs perfect accellerating with the linkage like you would under the hood of a car testing throttle thrap? it gets fuel, reves up in nutural, and when it is in gear and tied to the dock, it seems to have plenty of power to push the boat, this was being test by a boat mechanic at the dock, he never tried giving it gas from the throttle shifter, because he was at the back of the boat, adjusting and trying things out. I am only assuming that if everything works from the back of the motor as he tried , then it would be fine useing the throttle shifter like you do norm. when your heading out.but it did not work, so I don't know. I will try what you sugest to clear that possibility up. thank you

 

[oldrudedude]

Re: Strange Problem/need Help

JD, the throttle linkage on an outboard is different than on a car. On an outboard the throttle cable attaches directly to the timing advance lever on the right side of the motor. The timing advance lever has a cam on it that moves the carb butterflies. If you throttle up by using the cable, you cannot open the butterflies without also advancing the timing. However, if you are back at the motor, you can "cheat" by flicking the carb linkage to open the butterflies. If you do that you are not advancing the timing with the increasing rpm. I was just trying to clarify what you did back at the motor to get it to rev well when you were at the dock. It is very difficult to move the timing advance lever from the back without disconnecting the cable first.

Check out the fuel pump. It is highly suspect. At idle the fuel pump may be able to keep up. But, at open throttle does not get enough fuel to the carbs.

 

[JDs Dorsett]

Re: Strange Problem/need Help

Oldrudedude
thank you for explaining, you know I had a mechanic come down, and he did turn what looked like a cam with his hand, and it does make since to me what you said, he is the mechanic so I thought he knew what to do to check everything. I will mention to him that we should start with the fuel pump, it was my orig. thought. I had a vw bug, everything ran fine, went to get gas, then took off to go back up a small hill, and all of a sudden, no power to get there, ended up being the fuel pump, it was the same type of ordeal. thanks for your input, and time. folks are pretty nice on here helping each other out, it restores my faith in a seemingly dwindleing "good ole man kind"

 

[oldrudedude]

Re: Strange Problem/need Help

Come back and let us know how it goes with the motor. We are curious and learn from your feedbback.

 

[JDs Dorsett]

Re: Strange Problem/need Help

Hello,I will definately post the resaults when all is done.
I was down there today [dry storage] and pulled of the cover and called a parts shop to find out what a fuel pump costs, to my amazement, the guy told me that it you just buy the kit and re do what is there, you don't buy them on this motor just [re-build] so I will get the kit, cause I know if it does not need it now, it will at some point. better have ready for the mechanic, or me if i learn this.

 

[oldrudedude]

Re: Strange Problem/need Help

Post the model of your motor so we know what you are working on. It should be stamped on a metal plate on the left transom bracket.

 

[twinriver]

Re: Strange Problem/need Help

My 70 horse did this same thing, although I did not try opening the throttle with my fingers. I limped it to my mechanic and it turned out to be a hairline crack in the fuel line where it goes into the motor. A six inch piece of fuel line and I was running again. He did not want any money, but I gave him a twenty and my fish.

 

[four m]

Re: Strange Problem/need Help

my question is did the boat sit for a long time like over 10 months,if so the carbs are gumed up ,the high speed jet is in the bowl . a good way to find is go back out ,throttle up (hold on)then choke it because if its the problem the boat gona take off. if it does the carbs need to be cleaned. as for the fuel pump some time gas will come thru the exhaust (prop) if the diaphram is ripped.

 

[JDs Dorsett]

Re: Strange Problem/need Help

according to what I looked up, it is a 1978 70 hp, and the lable on the motor says the model # is 70773s serial # is jooo317 I am going to put a new fule line today, as someone posted my same thoughts about a tear in the line, it should be replaced anyway, starting to leave black on my hands from the sun hitting it.

 

[JDs Dorsett]

Re: Strange Problem/need Help

Hi, thanks for adding this, I am putting a new one on today, it was my thought as well, besides thinking it was the fuel pump, with everyones suggestions I might just get this figured out. thank you and everyone else I may have missed.

 

[JDs Dorsett]

Re: Strange Problem/need Help

Hi, the only info I have is from the guy I bought this from, he only had the boat 3 mo. then he was forced to sell he needed money, he had the same problem just before I bought it. I will tell the mechanic your sugestion, thank you

 

[Willyclay]

Re: Strange Problem/need Help

John, the experts on this forum are great and can help you fix any problem. While I am not an expert, I did experience a similar problem with a friend's 1987 Johnson 25HP motor. It started and idled fine but would not gain many RPM's when the throttle was advanced. We checked everything and found only a missing clamp on one of the fuel lines. After replacing the clamp, it ran perfectly. It is usually something simple and you just have to go through the trouble-shooting list eliminating issues. Good luck!

 

[restornator]

Re: Strange Problem/need Help

If 1 or 2 cylinders aren't firing, you definitely wont have any power. Also, if the motor revs up and you aren't increasing speed, prop might be slipping. I just wouldn't automatically assume its the fuel pump; the electrical components are the weakest link on these motors

 

[JDs Dorsett]

Re: Strange Problem/need Help

Willyclay:
thank you for sharing your story & your input, I hope it is one of the simple problems, as I have been missing alot of hot dates with some big Halibut out here on the west coast.

 

[JDs Dorsett]

Re: Strange Problem/need Help

restornator:
the motor was only reving up mostly in nuteral, we had put it in gear with the boat tied to the dock, it seemed to push the boat, we thought it was good to go as mention in my other posts, but it was only about 1/8 the throttle, so when I untied and headed out to try, it wouldn't increase the speed, it in fact acted like I was lowering the throttle. i am going to start with some of the quick fix possibilitys first and go from there. I do appreciate your input, as I really do not know very much but have been lucky over the years, and this is my 5th boat, the first one never gave me any problems, got spoiled I guess.

 

[Elbo]

Re: Strange Problem/need Help

Have you changed the spark plugs.Could be as simple as that.If you give it fuel but don't have enough fire to burn it,it will bogg down.Also you can read the plugs to see whats going on.If they are coated black. to much fuel,should burn off the plugs fairly clean.