1987/70 hp johnson traileritis

[smkonwatr]

My 70 hp johnson has a bad hesitation when I trailer it,Also sometimes when pulling skier ect. I have 115 to 118 lbs. of compression and moter tops out at about 5600 rpm with 13 3/4 X 15 SS prop.I wonder now much help if any would a Boyeson Power Reed kit be for this motor problem?

 

[JB]

Re: 1987/70 hp johnson traileritis

Howdy, Smoke

Welcome to iboats.

I am pretty sure your hesitation problem is not reeds and that aftermarket reeds wouldn't help.

It sounds to me like your synchronization between ignition and carbs is off.

Do a "link 'n' synch" procedure (carburetor linkage and ignition synchronization) . . .by the book. My guess is that will solve it.

 

[smkonwatr]

Re: 1987/70 hp johnson traileritis

I did link and ignition synk , I did not find anything out of spec. far enough that would cause my hesitation problem.As I was checking my pickup timing the no. 1 coil quit firing. I purchased new coil and am back in bussiness. I think that it is strange that the coil quit as I was timing motor as the coil was firing when I first begin timming engine.As The engine seemed to run a little lean I will go to a different idle jet to see if this will help my idle and mid range acceleration. I will not know how much this helps or not untill I put boat on water,as I live in Iowa it may be two months befor the ice is out so I can test run Motor. Thanks to anyone who may have a suggestion as to solve my acceleration priblem. Mike

 

[smkonwatr]

Re: 1987/70 hp johnson traileritis

I don't know if anyone is interested but I am about to give my relationship with this motor. I purchased 1985 motor(not a 1987 as I have said)mouted on 1987 lund Renegade 5 years ago. Motor had new prop and a bad hesitation at acceleration( motor would die on acceleration frequently. Had motor at Marina and was not fixed,I did compression check and had only 70 to 75 lbs. I tore engine down and found each piston had seised ring. I rebored 20th. and new wiseco piston, rings, bearings,rods gaskets,carb kits.Engine has 115 to 118 lbs. compression and about 50% of hesitation problem gone.I have put new fuel pump kit, mixed gas and eliminated VRO.Finaly I got a little wiser and begain changing props,this heped alot but I still have a hesitation problem so than I change idle and low rpm orfice. I have used this motor about once a week all spring summer and fall and it has been 4 years since I overhauled motor. Engine runs and sounds good at WOT but still has hesitation.Also last year the motor would only run at idle with hood off, after much research I found exhaust leak where power head bolts on. Upon repairing gasket this problem disappeared but still have hesitation.

 

[tashasdaddy]

Re: 1987/70 hp johnson traileritis

possible carbs.

 

[ezeke]

Re: 1987/70 hp johnson traileritis

Ask your service department to pull up OMC Service Bulletin #2188 3/87 so that you can read it.

It is likely that it may apply to your situation.

 

[smkonwatr]

Re: 1987/70 hp johnson traileritis

Called OMC dealer and he said the bullentin reads to synk and link and change idle orfice's. This is basicly were I am at. last weekend I tinkered with motor again and I noticed that when I lower tilt and trim all the way the motor runs rich. I think this is due to float bowl is over filling due to motor angle,I will need to wait untill I get motor in water and see if it sits level than. Just maybe I may improve motor if I set floats lower?
Thank You, Mike

 

[Dhadley]

Re: 1987/70 hp johnson traileritis

That may have a lot to do with it. Some additional things come to mind --

Can we assume you're at or near seal level?
What spark plugs are you using?
What is the timing set at?

5600 isn't a lot for that motor. Have you tried a higher X dimension (mount motor higher)?

 

[smkonwatr]

Re: 1987/70 hp johnson traileritis

I live in Iowa and we are at about 600 feet above sea level.I have installed champion QL77JC4 spark plugs.When I checked my synk and lynk I had between -1 and 0,I did adjust one turn and now have between -3 and-4.
It was my plan to test run motor and see if the one turn made a difference and than maybe I will change this on the water to see if it helps.My repair manual says Max. RPM is 5000 to 6000. I talked to local dealer and he thinks 5600 was a good MAX. RPM number.I don,t remember off hand but I think the high end timing is set at 19,I will check this number tonight.I could reprop to gain higher RPM but I dont feel compfortable traveling at a higher RPM and I dont want to lose any MPH as I boat on the Mississippi river and travel miles between fishing spots on occasion.
Thaks Lots, Mike

 

[tashasdaddy]

Re: 1987/70 hp johnson traileritis

your motor developes it's hp at 5000 rpms. but with the lousy, gas we have now, it will run better and cooler the closer you get to 6,000. 5,600 is not bad.

 

[Dhadley]

Re: 1987/70 hp johnson traileritis

Good choice on plugs and top end timing. Don't worry what the low end timing is. Just set the idle so you get the proper in-gear rpm. The wot timing is what we worry about. Don't go over 19.

You could stand at least a couple hundred rpm more on top. The motor will live much longer. However, I sure wouldn't reprop smaller to get it. That will only decrease efficiency. I'd raise the motor to increase the X dimension and reduce drag. That will improve everything from idle to top rpm.

 

[smkonwatr]

Re: 1987/70 hp johnson traileritis

I checked fuel pressure and found that at idle I dropped to 0 lb. and than up to 2lb and down again. With the help of this forum I swapped out VRO pump for non-VRO pump, since I had gone to 50:1 fuel 4 years ago.Well I think I am ready for the water. Thanks again, Mike

 

[smkonwatr]

Re: 1987/70 hp johnson traileritis

Just a recap of my post. Last fall when I last used my boat the motor run lean at idle.(if I hit the primer button the motor would pick up rpm's),When I tried to trailer boat the motor would die when accelerating(motor run lean at 1500rpm also).This winter I swapped out #28 idle orfice to #24,changed #1 coil,backed off pickup timing one turn to 3 degrees BTC,I put new spark plugs (gapped at .30),raised motor 3/4 inch (which puts me at aprox. 1/2 inch higher than keel,I swapped out VRO fuel pump(was getting varable readings at idle down to 0lb. and up to 2 lb. and than back down.) for non-Vro(now holding 1 3/4 lb. at idle). I was running 5600 rpm and 30 mph last tme out. Next time on water (maybe 2 weeks before ice out) I will check the tilt of my motor at WOT to check hieght of motor as to keel,also check WOT rpm,I may have to fine tune idle rpm in water,I will check that I have 19 degree timing at WOT and make sure my new fuel pump delivers enough fuel at WOT.I will also be aware of how motor idles at different tilts to see if motor runs rich or lean when trimed all the way against keel of boat.(I am thinking that when tilted beyond plumb the floats may alow fuel to over-fill or under fill-float bowl).I will repost at this time and I hope it will be good news. Thank you to all who have helped me with this project, Mike.

 

[tashasdaddy]

Re: 1987/70 hp johnson traileritis

keel, or do you mean transom,

 

[smkonwatr]

Re: 1987/70 hp johnson traileritis

I have a lot to learn,I mean the bottom of the boat at the transom.

 

[smkonwatr]

Re: 1987/70 hp johnson traileritis

Went fishing on the Mississippi river yesturday.Two guys in the boat,caught 2 saugers apiece(not too good),Motor seemed to perform well. Had 5850 rpm WOT,had good hole shot and never once hesitated under acceration.19 degree timing WOT. Thanks again for the good imput,I think all and all my motor problems have had different causes and the problem I was having last fall was the fuel pump not putting out at idle. I did not run the motor much yesturday but, I think it running real good.

 

[wavrider]

Re: 1987/70 hp johnson traileritis

Glad to hear and thanks for posting follow up. not often do we get the chance to find out the results. enjoy the boating season.

 

[smkonwatr]

Re: 1987/70 hp johnson traileritis

missprint on post #13. Post should read that timing is -3 degrees at idle(pickup point).