1984 Johnson 35hp tell tale at idle

[xBoomhauer]

Please bear with me here, I'm not looking for a definite root cause (I haven't gone through enough troubleshooting to give you guys enough info on the matter), mostly looking for verification that this is something I need to look in to.

I get a solid water flow from the tell tale at idle on a cold start. Once the engine is warmed up, I don't get good flow unless the engine is at elevated RPMs.

For example after trolling for 45 minutes (I know this likely isn't the best motor to use for trolling) I'm not getting any flow from the tell tale and am worried I am running the engine too hot if I stay at idle RPM. At this point I have to crack the throttle to get some water flowing. I worry about overheating since it sounds like the water boils for the first second or two after water starts to flow again. (passages obviously going to get hot with no water flow)

Video example of this for reference:
(I also feel like the motor makes an excessive metallic knocking/clicking noise while running. Not familiar enough with these motors to know if that's an issue or not, just something I've noticed in general)

Normal? I feel like even after the thermostat opens up I should still have a constant flow at idle? I've made sure the hose to the tell tale is clear, but have yet to go through the entire water system to check for blockages. I was also thinking maybe the water pump/impeller is worn out or weak and needs replacing, causing low water pressure.

 

[tphoyt]

You’re on the right track with worn impeller.
Any idea when it was last done?

 

[racerone]

When ever you get a " new to you motor " it needs a new impeller.-----Start with a compression test.----If good , install a new impeller NOW !----I used to troll with a 235 HP V-6.----Sometimes both engines in 6' waves.----Parts and pieces do not know how big a motor they are in.----Trolling all day long with that 35 HP won't hurt it in any way.

 

[xBoomhauer]

"It was replaced last season", so he says. With how relatively easy of a job it is, I was thinking about doing it anyway for the peace of mind (along with the lower unit gear oil). And with what you guys are saying I'm definitely going to get an impeller kit installed ASAP. Thanks for the confirmation/reassurance.

I'll report back once replaced.

 

[xBoomhauer]

Quick update.

Finally got around to pulling the lower unit off last night. My first time doing one of these. From what I could tell the impeller itself looked like normal wear, but a few things stood out:


-The copper tube came out with the lower, I was expecting it to stay in the motor. Maybe it was not connected properly up top or it was just seized on tighter at the bottom? Going to look into this.



-Pics of impeller/housing/plate




-The "o-ring" in the housing looked like it had been sitting out of its groove. Though there wasn't an obvious pinched section of seal like I would expect to see, if it wasn't in the groove when tightened down.



-I think the housing started to melt. The impeller cup looked sunken down slightly on one side, and what looked to be melted plastic next to it, and slightly up and over the edge on the side sitting lower (seen on the pic above)









Anything stand out that looks like it could have been causing my low water flow issue?

Going to try to verify the motor water passages aren't blocked before putting everything back together. I also want to get that copper tube reinstalled and put some water to it and make sure it's not leaking where it connects up top.

TIA for any insight

 

[flashback]

None of that was replaced last season, more likely last decade.

 

[tphoyt]

Yea it’s time for a water pump kit.
That impeller is toast. They should be soft and pliable and the fins should be straight. What you have is called set and you don’t want that.
The tips looked burned as well so it was likely run dry at some point and melted the housing.
Imagine back in the day going down a steel slide with a pair of shorts on. About half way down your ars catches fire and if your lucky you came to a stop before your shorts melted to the back of your legs.

 

[jimmbo]

Another Vote for that Impeller is Toast. A complete Pump Kit will have you on your way again

 

[xBoomhauer]

Good to hear.

The old impeller came out with a standard round metal pin vs. the crescent moon type key that came with the kit. Assuming that's normal and they're interchangeable? I plan on using the new one either way.

I will get everything cleaned up and put back together with new parts and let you guys know how it goes.

 

[xBoomhauer]

Welp, got everything put back together. Went down to the ramp to test it out and nothing was coming out of the tell tale. Only tried twice, idling it for maybe 10 seconds each time.

Everything went together well with the exception of the water tube. I had a very hard time getting the bottom of the water tube to line up with the grommet on the water pump housing while sliding the lower on. The water tube is pretty loose in the upper grommet. It doesn't want to fall out, but it flops around and is hard to get it to line up, even with the motor hanging vertically off the transom. Something doesn't seem right, though the height of the end of the water tube does seem correct.

I'm thinking that once I thought I finally had it lined up, the water tube actually slid next to the hole in the pump housing. So the water was just shooting out that hole.

I haven't taken the pump housing back off yet, since when I spin the shaft by hand the resistance feels like I am turning the impeller in the housing.

Not sure how easy it is to access or test the seal on that upper grommet for the water tube, I'm assuming it's not a quick job. I may try again one more time with an extra set of hands and make sure the water tube inserts into the housing.

 

[jimmbo]

To get to the Upper Grommet, the powerhead has to come off. Attached to it will be the Exhaust Tube(9) where the Grommet(115)is located, in the pics, you are looking at the Guide Tube(114)

I would attach a water supply to the Water Tube and observe for Leakage from the Guide Tube Area. Water will soon be pouring down the Housing, just from normal exits...

 

[xBoomhauer]

With the help of my brother I was able to get the lower unit back on while ensuring the water tube seated into the water pump housing. She's got water coming out of the tell tale now. The shift rod adjustment is all out of whack now though.

Going to get that sorted and then go out for a test run once I get the rest of the boat put back together. (Long story short almost had a small electrical fire due to some sketchy wiring/battery placement done by the previous owner. In the process of ripping out all of the old stuff and re-wiring)

Thanks again for the insight everyone.

To get the water tube to line up during installation, I used a section of stiff wire with the end bent into a hook. I used that to hold and guide the water tube as my brother slid the lower unit in. We did this with the motor tilted all the way up. There was barely enough of a gap to see the water tube as it slid into the pump housing. The wire was thin enough so at that point I could give it a pull to straighten out the hook bend in the end of the wire and pull it out. My upper water tube grommet is soft enough it allows the water tube to dangle around and seems like it would be nearly impossible to have it line up properly, even with the motor hanging vertical.

 

[oldboat1]

Should not guess at powerhead overheating. Get an infrared tester and look for an operating temp at top of cylinders around 130-140F. 160F is overheating.

 

[xBoomhauer]

Thanks for the heads up and info on that. I will plan on checking that next time I go out. I can already tell the water coming out of the tell tale is much much cooler than it was before doing the water pump. It would come out pretty hot, not enough to burn my hand but pretty dang hot. Now it gets warm to the touch but not hot. Fingers crossed I didn't run it too hot up until now.

 

[racerone]

Inspect / retorque head bolts.