70 hp rpm loss

[Javelin 353]

While ot today my 1991 70 Johnson suddenly lost rpm 5000 down to 2500. I tried to restart several time no luck. I unplugged the temp sensor,no change. While limping back to the ramp it took off back to full rpm then slowed again. Pulled pluggs all were black and oily looking.<br />All power packs and coils replace in October???<br /><br />How can I check spark By myself???<br /><br />Any other suggestions would be greatly appreciated.<br /><br />Thanks Jay

 

[B.autry4711A]

Re: 70 hp rpm loss

Javelin,<br /><br />How old is your fuel? If your fuel is old/sour that will definitely cause that. If so get rid of it immediately or you'll do more damge to your motor. Fresh 87, mixed with good TCW-3 approved outboard motor oil at 50:1 ratio or 16 ounces to 6 gallons of fuel. How old is your plugs?What about the filters? Are they cleaned? If your fuel is fresh, then did you squeeze the primer bulb to see if it picks up if so the fuel pump is bad. Did you bump the key in while this occured if it picked up then you have a fuel delivery problem or possibly fouled carbuertors.

 

[Javelin 353]

Re: 70 hp rpm loss

Fuel was fresh always use stabilizer.<br />Pumped key killed engine more.<br />Did not check primer bulb .<br />Plugs about 6 months old.<br />Boat rarely sits for more than a week or so.<br />I use pennzoil Blend oil. <br />Will check replace fuel filter tommorrow.

 

[B.autry4711A]

Re: 70 hp rpm loss

Javelin 353,<br /><br />Check all of your fuel filters including the fuel pump filter. I never checked mine until I got a SELOC manual and it says to check that fuel pump filter it is part of the tuneup maintenance. It is a large sized screw that is a flattop or slotted head remove that and make sure you catch some of the fuel. Under that cap which is black on mine motor is a fine round screen the same diameter as the cap. I blew mine out with my compressor and cleaned the area under the cap out and reinstalled it. Make sure after you install it to pressure check it by squezzing hte bulb. Mine leaked and I had to reset it and it was good to go. I checked mine for the first time in over a year having my boat and it had alot of crud in it. I think that might have caused it to run slightly rough at idle because I consider it a partial fuel restriction as the main line from the fuel tank runs directly into the fuel pump. I can'yt wait to crank her and see if she is running better than before. I see you are from Raleigh, N.C. very nice place I love driving through the Carolina's I grew up in Fayetteville, N.C. my father was stationed at Fort Bragg there. He is retired and I am stationed in Illinois, Scott AFB. Not bad assignment.

 

[B.autry4711A]

Re: 70 hp rpm loss

Forgot to mention one more thing,<br /><br /> have you changed out your water pump? If you haven't your motor could be overheating and that is why you could have slowed down in RPM did your overheat alarm go off if it is working. You can determine if the overheat alarm is working by grounding out the wire TAN color comming off each head and make sure the key is turned to on but the engine not running.

 

[Javelin 353]

Re: 70 hp rpm loss

New impeller and t-stat October, The Horn will sound when grounded.<br /><br />Big Bubba thanks very much for your service to this great country we live!!!!!!

 

[B.autry4711A]

Re: 70 hp rpm loss

Thanks you Javelin 353,<br /><br />If I had to do it again I would serve my country. It has been a great and rewarding career. I hope I have helped you out with your boat. I am by no means a master mechanic but I have learned alot from this outstanding forum and these guys have saved me alot of money and my baot runs pretty good. Thank you and everyone on this forum.

 

[Javelin 353]

Re: 70 hp rpm loss

How can I check spark working by myself?????

 

[OBJ]

Re: 70 hp rpm loss

Couple ways Javelin.<br /><br />Check the thread link below. It will show you a pic of a homemade spark tester....pretty neat...<br /><br /> http://forums.iboats.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=28;t=038398 <br /><br />Another way will require the help of a friend. Cut the head of a 10penny nail and stick the end of the cut off nail into a spark plug boot. Using insulated pliers, hold the sharp end of the nail about 7/16 to 1/2" away from any clean engine ground. Have your helper crank the engine. You should see a hot lighting like spark snap across the gap.<br /><br />You can also purchase spark testes from any good auto parts store. These usually will test one plug at a time.<br /><br />Your problem sounds a little more ignition related than fuel...."pumped key (choke) and killed engine more"....would kinda' indicate flooding the running cylinder.<br /><br />A service manual, OEM preferred, would be a good addition to your engine.<br /><br />EDIT: Just another thing.....get a set of compression readings. Even if all the holes are good, it would be handy to have a set for future reference.

 

[Javelin 353]

Re: 70 hp rpm loss

I will check compression I have a manuel also Selco. What compents are related to ignition besides coils and powerpacks??

 

[Javelin 353]

Re: 70 hp rpm loss

???? trying to beat the board shut down today!

 

[OBJ]

Re: 70 hp rpm loss

Timer base and charge coil. Both under the flywheel. But get a look at all the sparks and get a compression reading on each hole. Rule out as much as possible first. If your missing a spark on a cylinder, you can swap ignition coils to see if that maybe the cause. Or, using a multiple spark tester, you can swap igniton coil leads around from the power pack. This can help narrow the problem down. DO NOT try and start the engine with ingnition coil leads swapped around.<br /><br />Yeah.....throwing a bunch of stuff at ya' here before the forum goes off too......

 

[Javelin 353]

Re: 70 hp rpm loss

Thanks OBJ I have some old coils to use if i need to swap them out

 

[OBJ]

Re: 70 hp rpm loss

Raliegh huh? I'll be down at Kerr Reservoir in April. Like that area.

 

[Javelin 353]

Re: 70 hp rpm loss

Do not go to kerr often, striper fish up their some, I found the problem Yesterday, the middle cylinder had weak spark at the end of the plug wire, changed coil, same thing, moved the plug wire and the problem moved, replace all the wire with new oem wires, cleaned and tightened all connections ran some omc engine tuner in here and took her out for about 35 min of hard running no problems then a bad storm blew up, gonna replace the key swith this weekend just to feel better about that part.<br /><br />Thanks again OBJ!!<br /><br />Javelin 353

 

[Javelin 353]

Re: 70 hp rpm loss

1 more thing compression 115 all 3 holes

 

[OBJ]

Re: 70 hp rpm loss

Thanks for posting the fix Javelin. We like to hear about them so maybe someone else can benifit from your experience. <br /><br />We go mostly for Bass and Crappie. We've gotten into some Stipers on occasion but don't specifically fish for them unless we see boiling water........MAN! That's a blast!!<br /><br />Again...thanks for the post!

 

[B.autry4711A]

Re: 70 hp rpm loss

javelin 353,<br /><br />Good day to you. I am glad you found the problem. So as I am reading your solution to the problem you found a bad wire. I have a 1989 Evinrude 88 horsepower that will load up sometime when I am operating it in the driveway if it hasn't been cranked in a while but clears itself up. But since then I have found the fuel pump screen was really dirty and I have cleaned that out but haven't cranked it lately since then hoopefully that is what caused it to load up at idle. Glad you were able to fix your problem. Take care

 

[mark.aa]

Re: 70 hp rpm loss

had similar problem on my 89 vro 60hp johnson but found fault was fuel pump diaphram rubber coating broken off and found it,s way into carb needle valve float seat,s ,starving fuel intermitantly,new pump pump and carb kit fixed it.

 

[Javelin 353]

Re: 70 hp rpm loss

Where is this fuel pump screen located, how much disassembly work is envolved, going to try and find my manuel ??