'08 Optimax 115 overheating issue

Riddickulous

Cadet
Joined
Nov 20, 2011
Messages
6
I have an '08 Optimax 115 and had some very odd water/overheating issues yesterday. I'm cruising up the Bogue sound at 5100 rpm, sound temperature is 58 degrees and I flipped through the SmartCraft and made a comment to my buddy that it was amazing to me that an engine could run at 93 degrees and that there must be a ton of flow going through it. Not 5 minutes later an alarm goes off, I quickly scroll through and see it is at the 160 degree point of the alarm and before cutting it I happen to glance back and notice a fairly decent flow out the pee hole.

We sit long enough for it to cool down to about 130, crank it and get a reasonable stream and it seems to be cooling down a little initially. We get underway and I was only able to do about 2000 rpm with the temperature going back and forth between 140-150 (thermostat opens at 145 I believe). I tried to give it more throttle and it pretty quickly jumped above 150, pulling back on the throttle brought it down. Pressure as indicated by the SmartCraft was about 11psi at around 2000 rpm and the stream seemed to be the same as its been all summer (just got the boat in May). We get a few miles down the sound at this near troll speed and the temp shot up to 160. I'm not sure if I had flow at this point as I was poking around on my phone looking for what the water pressure should normally be. I let it cool again for a bit and this time no flow out the hole but seemed like I could see vapor/exhaust coming out.

After a tow back to the dock and back to the house I hook up the garden hose and water flows out the pee hole and I hear a couple of clicks as if something was opening or closing. Let it run for 10-15 minutes and I crank it up and after cranking it the flow out the pee hole immediately beings to slow as if the passage is going closed and finally it stops. Motor has 206 hrs on it (20 by me this summer) and likely has never had the impeller changed.

I talked to some guys at work and two of them independently said the driveshaft could be spinning in the impeller and this would cause the intermittent issues. Any other ideas?
 

jerryjerry05

Supreme Mariner
Joined
May 7, 2008
Messages
17,923
Re: '08 Optimax 115 overheating issue

If the driveshaft was spinning in the impeller it would overheat fast,I've only seen this once in almost 30 years.It was a 5hp.
The impeller is probably shot.Not a big job.Fill out the profile you might be close to someone who can help.
 

Riddickulous

Cadet
Joined
Nov 20, 2011
Messages
6
Re: '08 Optimax 115 overheating issue

Filled out the profile. I have a Newport address but I claim Morehead City. I'm a few miles from Brandywine Bay for those of you in the area. I'd be interested in compensating someone (in beer or money) that has this motor (or one of its siblings with the same guts) and has done some water pump maintenance on their own before that wouldn't mind coming over and at least pulling the LU off with me and getting the pump housing off to have a look at what we find to give me an idea of if it will be a simple replacement of the impeller and/or housing or if I have other problems higher up with either the thermostats or the poppet valve. I'd just pull it myself but sometimes I have a real bad habit of not remembering which little piece went where and it would be nice to have someone that has done this before for some guidance.

Additionally, if anyone knows someone that does mercury outboard work on the side that would be fine as well. Just trying to avoid paying dealership labor and markup for something that could be so simple.
 

Riddickulous

Cadet
Joined
Nov 20, 2011
Messages
6
Re: '08 Optimax 115 overheating issue

I got the LU off and this is what I found:
IMG_20111203_121056.jpg

IMG_20111203_121121.jpg

IMG_20111203_121248.jpg

IMG_20111203_121305.jpg


Scoring on the housing = need a full kit, right?
 

CharlieB

Vice Admiral
Joined
Apr 10, 2007
Messages
5,617
Re: '08 Optimax 115 overheating issue

New SS parts and impeller should have that puppy pumping like new again.
 

Riddickulous

Cadet
Joined
Nov 20, 2011
Messages
6
Re: '08 Optimax 115 overheating issue

Just wanted to update this for anyone coming behind searching for answers. Some boat buddies at work suggested sticking the impeller back on the shaft and seeing if I could easily turn the impeller without turning the shaft. Sure enough, the impeller was slipping around the shaft without a lot of effort. My buddies idea for this was that if the shaft were slipping in the impeller then it would occasionally turn it causing flow out the tell tale at idle but would likely get worse as I ran faster and water was being rammed harder into the pump housing causing the impeller to slip. I didn't notice it when I posted the pictures but if you look in the third pic at around 7oclock on the impeller bushing you can see a little crack that was probably the root cause of the slipping. A new impeller, plate, and gaskets and 3 hrs of cruising around several weeks ago and no high temp alarms so I'd say it's fixed.
 

17rogue70

Petty Officer 3rd Class
Joined
Feb 21, 2010
Messages
93
Re: '08 Optimax 115 overheating issue

a friend of mine here in florida had the same issue EXCEPT his impeller seperated from hub in the impeller . same scenario high temp when cruiseing and cool at idle. new pump kit and its fixed
 
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