65hp Johnson '72 Cold starting nightmares

[bubbster]

I could do with some advice on how to get my motor warmed up right. Once warm it runs perfectly, and restarts instantly for an hour or so afterwards. But when I first get it into the water it is a real beast to get running. It starts immediately, and will run for about 30 seconds before starting to falter. If I put it into gear, it dies. Normally just after we have cast off, among the moorings. It then will not restart! The same happens if I wip the cover off, and give it some full throttle manually in neutral to blow out some smoke for 30 secs or more. It will then idle ok, but when I put it into gear and try to pull away it dies a few more times.

So far I have been lucky and have got it running just before being in real trouble, and it will falter for a bit as I open the throttle as far as I can in the moorings, but then it will suddenly clear and run smooth. At which point I can idle again no problem and she runs like a dream!

How can I fix this? Or at least get the engine warmed up prior to launch? I am beach launching which means I quite often don't have the depth to start her up whilst tied up.

Any tips appreciated!

 

[jtexas]

Re: 65hp Johnson '72 Cold starting nightmares

What's your compression?

It's hard to tell -- seems pretty normal to me...especially if it "starts immediately." She really does need to warm up for a minute or two or three. or four. with the hi-idle lever up part way. When it starts to falter, punching the choke should keep it running.

Are the choke plates staying open except when you engage the choke?

You can't run it long enough to warm up while still on the trailer?

If it really does take longer than normal to warm up to operating temp, check the thermostat.

It idles fine after warm-up?

 

[bubbster]

Re: 65hp Johnson '72 Cold starting nightmares

It idles fine once warmed up. I may well be trying too hard here, and not waiting for it to warm up. But I struggle to keep it running on warm up without revving it in neutral. However I have not yet used the choke? It starts fine without it, with only a little of the warm up lever. Once it cuts out, I have to reduce the warm up, as otherwise the engine override prevents it from turning (I assume this is to prevent flooding) - and so I have assumed the choke is not needed?

I think I need to work out how to warm this thing up! The problem is that I need to get the boat off the trailer in order to find the depth to drop the engine at my local harbour.

I was wondering if this may be related to the pre-warmup autochoke( if fitted)? I think I read something about this being a SB from OEM? This engine has been in the family since new, and I don't think has been serviced by a dealer since c1975? So it may not have been disconnected??

 

[tashasdaddy]

Re: 65hp Johnson '72 Cold starting nightmares

it sure sounds like it could be the auto choke. i believe you disconnect the purple yellow wire on the connect buss bar.

 

[bubbster]

Re: 65hp Johnson '72 Cold starting nightmares

Is this related to the Manual choke knob on the engine? It has on, Automatic and off setting. The manual recommends leaving it in 'Automatic'?

Or does this effect the choke toggle at the remote?

Thanks for any help!

 

[jtexas]

Re: 65hp Johnson '72 Cold starting nightmares

Is this on a RIB? Never beach launched before, having a hard time picturing your situation -- can you not get the water intakes submerged while the boat's on the trailer?

If I recall (and tasha'sdad will correct me if I'm wrong), "On" holds the choke plates closed, "Off" holds 'em open, and "Auto" holds the choke plates half-way closed until the engine warms up, plus enables the toggle on the remote to close 'em completely.

The automatic choke solenoid has two wires, a purple/yellow leading to the heat sensor controlling the "automatic" feature, and a purple/white connected to the choke toggle. The heat sensor gets dodgy over time, causing the choke plates to stay 1/2 closed all the time (or some of the time, or most of the time) -- I suspect this is what's happening.

The SB you cited says to disconnect the purple/yellow from its terminal on the terminal strip and connect it on the same terminal as the purple white.

The result is a choke full on or full off, controlled by the toggle at the remote.

The thermal switch was dropped from the design early to mid-70s. The cold start procedure is: hi-idle lever fully up, engage choke while cranking, release it when the engine starts. Give her just enough gas to keep her running while she warms up, and if she falters, punch the choke just for half a second.

Can't say for sure you'll need "full" hi-idle -- myself, I'd start there and use trial-and-error to find the sweet spot. Or somebody else who knows better will chime in.

Let us know if this works.

 

[F_R]

Re: 65hp Johnson '72 Cold starting nightmares

Is this on a RIB? Never beach launched before, having a hard time picturing your situation -- can you not get the water intakes submerged while the boat's on the trailer?

If I recall (and tasha'sdad will correct me if I'm wrong), "On" holds the choke plates closed, "Off" holds 'em open, and "Auto" holds the choke plates half-way closed until the engine warms up, plus enables the toggle on the remote to close 'em completely.

The automatic choke solenoid has two wires, a purple/yellow leading to the heat sensor controlling the "automatic" feature, and a purple/white connected to the choke toggle. The heat sensor gets dodgy over time, causing the choke plates to stay 1/2 closed all the time (or some of the time, or most of the time) -- I suspect this is what's happening.

The SB you cited says to disconnect the purple/yellow from its terminal on the terminal strip and connect it on the same terminal as the purple white.

The result is a choke full on or full off, controlled by the toggle at the remote.

The thermal switch was dropped from the design early to mid-70s. The cold start procedure is: hi-idle lever fully up, engage choke while cranking, release it when the engine starts. Give her just enough gas to keep her running while she warms up, and if she falters, punch the choke just for half a second.

Can't say for sure you'll need "full" hi-idle -- myself, I'd start there and use trial-and-error to find the sweet spot. Or somebody else who knows better will chime in.

Let us know if this works.

Sure sounds like it is a candidate for the choke modification. As already said, at the terminal strip, locate the wires coming from the choke solenoid. Remove the purple yellow (coming from the solenoid) and connect it along with the purple whites. From then on, it will only choke when you operate the toggle. You will probably have to momentarily "bump" the toggle a time or two to keep it from coughing and dying right after starting. Bumping the toggle is doing what the warm-up circuit is supposed to do, but you have control over it. And you probably will have to choke it to get the initial start.

Choke knob stays in the "automatic" position, even though the automatic feature is disabled.