Starter motor turning so slowly (35hp '77 Johnno)

[McBarry]

Hi,<br />trying to convert the above to electric start.<br /><br />Have "borrowed" parts from 25hp '76 Johnno - starter motor and bracket(had to modify slightly to fit), starter and choke solenoids, neutral switch.Motor already has points on it....<br /><br />Before I describe the symptoms/my faultfinding results etc, is this starter motor "big" enough to crank my 35hp?<br />it's got 2 brushes but my manual for the 35hp elec start shows 4 brushes - ?? a bigger starter motor needed for the 35hp??<br /><br />Here's the symptoms - turns over nicely, but sooo slowly.. like battery is flat.(it isn't...)<br />so voltages--<br />12.5v at terminals at rest.<br />10.7v " " on cranking.<br /><br />12.5v at starter solenoid input on cranking.<br />5v at starter input lug on cranking. (to eliminate solenoid, I direct connected battery to starter bypassing ALL wiring - same slowww response.<br />took flywheel off and cranked - starter spins beautifully (didn't do voltage measure - should I have???) - so it dies badly under load..<br />Given the symptom exists with original wiring or using short lenghts of new battery wire I guess rules out wiring anomalies.<br /><br />Which leaves me with starter motor failing under load. <br />???brushes??? not much else I can think of??<br /><br />Sorry about super long post - figure get you guys heaps info up front to help me if possible..<br />Thanks again,<br />David

 

[JB]

Re: Starter motor turning so slowly (35hp '77 Johnno)

G'Day, McBarry.<br /><br />A little confused about your report.<br /><br />1. 10.7V at the battery and 5v at the starter when cranking?? Where did the other 5.7 volts go? It must be lost in a resistance in the circuit.<br /><br />2. When you say you bypassed all wiring, does that include the ground portion of the circuit?? Did you connect battery ground directly to the starter case?<br /><br />It sounds to me like there is resistance in getting battery power to your starter motor. On a new installation I would suspect the electrical connection of starter to bracket, bracket to engine block, engine block to ground cable or the cables themselves.<br /><br />Good luck.

 

[rickdb1boat]

Re: Starter motor turning so slowly (35hp '77 Johnno)

Jump all the way from the battery to the starter to eliminate bad wires and loose or corroded wiring. Heavy jumper cables will work. But I bet JB is right...

 

[DJ]

Re: Starter motor turning so slowly (35hp '77 Johnno)

McBarry,<br /><br />You mentioned that you had to "modify" the mounting bracket. Is the starter binding against the flywheel?<br /><br />Otherwise, I'm with JB and Rick.

 

[McBarry]

Re: Starter motor turning so slowly (35hp '77 Johnno)

Thanks guys,<br />sorry 'bout confusion..<br />bypassing wiring was done by 1m battery wire from battery +ve to starter input lug, but I didn't ground the starter case directly.<br />Also, "modifying" entailed some grinding to get the bracket to fit snug onto the engine block, BUT, and this may be significant, had to use spacers on the 2 long mounting bolts to drop the starter down out of the bracket by about 5mm otherwise it wasn't disengaging from the flywheel at rest. Maybe it needs the top of the starter to be up in the bracket housing to make a good earth ???<br />And yeah JB - I'm really perplexed about the vanishing 5v??!! My meter leads died too so tomorrow morning(it's 2.30am here...) plan is some new meter leads, ground starter case directly and go from there.<br />I'm hoping the starter-to-bracket resistance is sky high to solve the problem - man I'm frustrated with this one...<br />If it's not, where would U guys look?? I mean, not much else to investigate??or likely I've overlooked something obvious..<br /><br />Thanks,<br />(very frustrated and annoyed),,, Dave.

 

[bidlimit]

Re: Starter motor turning so slowly (35hp '77 Johnno)

I had the same problem with my '76 35hp....The starter turned but did so in a very slow manner. I took it apart and the brushes were worn down to nothing. I just replaced the whole motor because the bendix was shot and the commutator was also. Anyway, try inspecting the brushes and also check out the commutator. There are about six thin slots on the face of it that get clogged very easily with brush material. If they are clogged, the motor is shorted more than it needs to be and runs at reduced power. You can use a sharp ice pick to clean them out. Than sand it clean with 400 than 600 grit sandpaper. Reassemble the motor and grease the bushings. Also check the cable from the solenoid to the motor case, they weaken at the sharp bend where it connects to the motor case. Hope this helps.

 

[ob]

Re: Starter motor turning so slowly (35hp '77 Johnno)

Insure that the starter bendix is not binding when manipulated by hand to the flywheel teeth and that it will disengage freely,which it sounds like you've covered.If your concerned as to whether you are not getting good ground between starter case and block,check with your ohm meter in the R X 1 scale.Should peg out to 0 ohms.If not ,you got a ground issue.If it reads 0 ohms ,proceed ,as Rick suggested, and run you some known good cables from a known strong 12 volt battery,neg. to the engine block for ground and the pos. cable to the terminal post of the starter.If it cranks weak,you got starter problems.If it cranks strong ,you got wiring issues.<br /><br />Be extremely careful around flywheel when performing .

 

[McBarry]

Re: Starter motor turning so slowly (35hp '77 Johnno)

MAJOR SUCCESS !!!!!<br /><br />THanks for the replies and ideas.<br />The mechanics of the starter were/are fine - drive gear sliding up/down the shaft freely (thank goodness..)<br /><br />At first light today I sussed the ground wire. Rather than checking volts across it, I checked for a drop along it ie - meter lead on the battery neg and other meter lead on the cable to motor chassis connection.<br />Guess what...well JB nailed it...I was losing 4 to 5 volts because of that #$*%$ cable. !! Inspected inside the OK looking terminal connection - corrosion city!!<br />Then I got all obsessive and pulled the starter apart, cleaning thoroughly the joins at either end of the body where both end plates sit. Then gave the 2 long mounting bolts a clean and emery paper, ditto the 2 spring washers(did I mention obsession setting in....LOL), checker brushes(plenty length, good surface cond and free movt in brush holders), and reassembled. Again...<br />Bought some new battery cable, soldered lugs on ends (obsession again...) and fired it up.<br />Amazing difference. NO lag for a millisec as the starter winds up, just BAM! away it goes.<br />Now to give it some fuel and see what happens.<br /><br />The main thing which helpes was measuring voltage drop along the cable ie I already knew there was a fat loss somewhere, just didn't know where..<br />Thanks for all replies and ideas - much appreciated.<br /><br />Regards,<br /><br />David<br />PS ; did OMC make a flywheel for the 35hp which accommodated manual and elec start together - like on the 25hp model??<br />Ta

 

[ob15]

Re: Starter motor turning so slowly (35hp '77 Johnno)

Looks like another happy ending. Gotta love it.