Home › Forum › Ask A Member › 9.9/15 impeller housing tricks?
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March 27, 2015 at 3:08 am #12842
Well I finally got this motor back together. Long story short the old thermostat must have been malfunctioning, and/or the impeller was toast. This being my 1st 9.9/15 true project, it certainly taught me a great deal. The following had to be done, but once it was back together tonight, voila! Started up on 2 pulls. Everything operated correctly, less a couple of weeping new gaskets, which just required a little extra tightening on their respective covers.
Before I list off everything that had to be done – my question to you all: I have observed that when installing new gaskets, they sometimes leak. Particularly the water jacket gaskets. Any tips on how to solve this? I usually install them dry, and I’ve seen this happen on a number of different models. Should I be slathering on perfect seal on these dry gaskets? I’ve heard a few people use a small amount of silicone/marine sealant, since it will not be in contact with gas. I figured crankcase seal would be overkill, and getting to liberal could easily foul various passages.
Here’s what I had to do to get this baby back into service:
1. Replace transom bracket assembly completely
2. Replace both transom tightening screws
3. Replace tiller gear and remanufacture from scraps/scratch (that was an interesting macguyver, but works great now!)
4. Replace inner tiller gear after drilling out – old one was frozen in from salt
5. Drill out tiller connector, the little plastic one
6. Replace tiller grip
7. Remove, replace kill switch and reroute
8. Reinstall powerpack and coils; reroute and rewire external ignition parts, retainers, and clips
9. Replace manifold due to stripped out manual starter orifice
10. Carb was…OK
11. Replace breather box
12. Replace all gaskets at the powerhead, less the exhaust gasket
13. New thermostat
14. New Impeller
15. drill out and retap 1 head bolt
16. Repaint the motor cosmetically
17. Free up the cowel latch, frozen
18. Of course, clean off and re-mate the water jacket bypass, thermostat cover, cylinder head, manifold surfaces
19. Completely rebuild and repair the manual starter (a lot easier than the 9.5’s)
20. Replace all fuel linesSurprisingly for this being a salt water motor, the internals were all OK, and almost no screws were stuck including powerhead, exhaust, water jacket, and even the gearcase was free. The transom bracket had actually corroded to the point where it was turning to dust and broke in half. All tiller hardware was a complete loss and replace, it was cemented in beyond salvage – thank god for parts motors. Even though this motor turned into a 20 hour job, it was a good investment in terms of learning about these motors. I have a bunch more to go through and the subsequent ones will certainly move along much faster now. Next time I’ll know just to pull the powerhead and switch to a different leg and pan, and toss the original pan/leg into the scrap pile.
So let’s just say I feel pretty confident around these motors now…except Donny…you got me all nervous about the newer cable throttle assemblies when they updated the tiller hardware in ’85!!!!!!!
March 27, 2015 at 10:47 am #12854Well, those exhaust gaskets are tricky, because the inner exhaust cover in not flat inside and is a pain to clean/true up properly.
First, I would recommend that the powerhead be removed in order to be able to get at all the surfaces and do a better job, nearly impossible with the powerhead installed on the midsection. Be sure to true up the flat surfaces, like the outer cover, and the flat side of the inner cover, along with the block. Keep in mind that the water passage walls are kind of thin, so be sure to inspect these surfaces carefully. In other words, you should be concerned about internal water leaks into the exhaust chamber, not just external leaks. Consider replacing the inner exhaust cover if sealing is questionable.
Probably a good idea to remove the plastic elbow while the cover is off, replace it with a new one. The only reason I mention this is that you will be in a real mess if the old elbow snaps off/leaks once the powerhead is back in place on the exhaust housing. Be sure to clean all the threads, and bolt shanks in salt water units.
Please do NOT use silicone or any other goop, use the OMC/Merc perfect seal gasket sealer only.
All that being said, I have never really found a cooling problem related to problems in the exhaust cover cooling passages. So, it might be best to "leave well enough alone". I surely have seen crappy jobs that had to be redone when people pull this cover off though. And, I have opened "Pandora’s box" a few times when I removed these covers.
And, once again, remember that the early 9.9/15s (74-78) had NO upper water tube grommet issues, the problem was introduced in 1979 when the grommet design was changed, the original grommets are no longer available. So, I usually leave an original ones in place, without trying to pull out the water tube. Keep in mind, that the original grommet has probably been replaced with the crappy grommet if the powerhead has been off before. -
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