Alpha I Gen II impeller change

Fairly new boat owner here.. while summerizing the boat, i started the motor and ran it for about 30 seconds without the muffs on. It's been 2 seasons since ive started it up and didn't think it would hurt anything. After reading the manual after doing this, i was worried i may have damaged the impeller. I took it out on the lake and saw normal temps (175 degrees) at idle, but noticed it would rise slightly to 180 or a little over, above 3000 rpm's. I couldnt remember if this was normal or not because it had been a couple years since i ran the boat. So i decided to change the impeller for ease of mind.

During the impeller replacement last night, I found the top housing seal to be good and intact. The impeler itself looked great, no noticable defects other than it not fully straightening all the way after removal. I noticed the factory faceplate under the impeller housing was 1 piece with rubber on both sides and no sealant, instead of the 3 piece gasket/faceplate that came with the kit. The factory faceplate/gasket looked to be in perfect shape (engine only has 36 hours on it) so i decided to reuse it and avoid getting any perfect seal on my drive for ease of future replacements. I added perfect seal to the 4 housing bolt threads and torqued them. I'm wondering if anyone else has ever reused this rubber faceplate gasket. I probably wont be putting more then 20-30 hours on the boat this summer.

There was also an orange coating on the new water tube o-rings that partially rubbed off when i installed them. Curious if this will affect anything, but not too concerned. I put it all back together and re-serviced the gear lube, and im now wondering if i should just go start it up on the muffs and check for leaks or just take it out on the lake and hope for the best?

2009 Crownline 185ss
Merc 4.3 TKS, Alpha I Gen II

Re: Alpha I Gen II impeller change

It just takes a minute to start it on the muffs and verify seaworthiness.

You sound like you are being careful in your mechanical endeavors, and you wouldn't be the first to re-use parts, although the official answer is always to replace wear items. That is not always practical on regular folk's budgets.

Re: Alpha I Gen II impeller change

GaryMc73 said:

if i should just go start it up on the muffs and check for leaks or just take it out on the lake and hope for the best?

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Start it up on the hose, watch for good consistent water flow coming out the idle relief ports, let it warm up to normal operating temperature and verify it does not run hot.

The orange must mean something but always seems to rub off.

My 2005 which has the 4.3 but is mpi, not tks, will get to 175 as normal operating temp then when I get over 3000 I will see the gauge go up slightly then usually settles back down to about 175.

Here's the service bulletin that Merc put out on the procedure for proper operations on a hose.
http://www.boatfix.com/merc/bullet/99/99_09.PDF

Mark

Re: Alpha I Gen II impeller change

ran it today on the muffs, ran good with a rock solid 175 degrees on the gauge (Faria) at about 1200 rpms. no signs of any gear lube leaks anywhere. Taking it out on the lake tommorow for the real test Before the impeller change it would sometimes spike up to 185ish degrees at WOT.

Re: Alpha I Gen II impeller change

Looking good there Gary.

Let us know how it comes out.

Mark

Re: Alpha I Gen II impeller change

temps were good on the lake, it stayed 175 degrees under 3000 rpm, and only went up to maybe 178 over 3000-WOT. It never went over 180 like it did before the impeller change. A little surprising because the impeller i replaced looked great. Drive lube dropped about 1/8" in the monitor by the end of the day but i suspect it was just air bubbles being purged.

Re: Alpha I Gen II impeller change

GaryMc73 said:

temps were good on the lake, it stayed 175 degrees under 3000 rpm, and only went up to maybe 178 over 3000-WOT. It never went over 180 like it did before the impeller change. A little surprising because the impeller i replaced looked great. Drive lube dropped about 1/8" in the monitor by the end of the day but i suspect it was just air bubbles being purged.

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Looks can be deceiving but just keep the one you took off on-board as a spare just in case.
Maybe also by simply doing the r&r with new gaskets, tightening, etc. that helped seal it all up properly.

Good work

Mark

Re: Alpha I Gen II impeller change

I wouldnt keep a used impeller as a spare, even if it "looks" good. if the vanes are "set" (i.e. curved and wont relax to straight), then keep it as a souvenier or put it in the bin.... Buy a new one for a "spare"....but if you are going to do that, might as well get the kit as a spare, to have the right gaskets to put it all back together (along with new oil and a new drive -to-bell housing gasket set..you'll need those, too.)... JMHO...KTB.

Re: Alpha I Gen II impeller change

ktbarrentine said:

to have the right gaskets to put it all back together (along with new oil and a new drive -to-gimbal housing gasket set..you'll need those, too.)

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Just for clarity sake, the drive connects to the bell housing not gimbal housing.

If the vanes are set, then it would not qualify as looking good. Keeping used parts (especially small ones that store easily) is a good way to see "trending" between maintenance periods of like items. It can be interesting what might be seen.

Mark