3.0 omc runs hot

[BIGTUCK]

So I got a 1975 Ozark Boat Works 17 ft, model 170, tri hull with a 140 horse 3.0 GM motor. From what I gather it has the 400 series lower unit.

I have fixed everything on this boat that was wrong or needed replaced including starter, carb, lower tilt motor, solenoids, fuel pump and carpeting. I am already in for the long haul on this thing and want it running top notch. So I put all this time money and effort into this thing, had it running good, and now all of a sudden it runs hot. This is my first boat and while I have lots of automotive experience, I don't know a lot about boats. So I need to know where and if my boat has a thermostat, and a breakdown on the schematics of how the water circulatory system operates on this thing. Oh yeah the lower unit only has about 20 hours on it and the oil is fresh as the guy I got it from stated he just had it rebuilt. Sorry for the long post just wanted to make sure you had plenty of info to go off of. Thanks, BIGTUCK
Here is some pics of the old beast

 

[bjcsc]

Re: 3.0 omc runs hot

Hey welcome to iboats! What a clean rig! Looks like you did a good job so far. You do have a thermostat, it's inside the housing on top in the front that three hoses go to. Did you replace your impeller?

 

[whywhyzed]

Re: 3.0 omc runs hot

Agree- you need to replace the impeller in the outdrive. And now you need to take the thermostat housing off and look for the chunks of rubber...well, see what it looks like when you get the old one out.

To do this job you need a manual -it's 30 odd pages and we can't type very fast... the Seloc manual is ok, proper OMC one off eBay better, Clymer one not recommended.

Definitely gotta name that boat the "Ozark Mountain Daredevil"

 

[BIGTUCK]

Re: 3.0 omc runs hot

no I havent changed the impeller. is it hard to change? I am assuming the impeller is the main water pump for the whole engine and the actual engine water pump just circulates water through the motor? would the impeller just go out all of a sudden? thanks for all the help

 

[Fishermark]

Re: 3.0 omc runs hot

"would the impeller just go out all of a sudden?"

Yep. Especially if it has been sitting up for awhile. The rubber vanes get hardened and then break off when used.

 

[BIGTUCK]

Re: 3.0 omc runs hot

So I just pulled the thermostat and put in some water on the stove and it opened normally so I guess that leaves the impeller. Oh and there was no standing or water that came out when I removed the hoses, so I guess I need to find a manual for this thing and order an impeller. Thanks for all the info guys!

 

[BIGTUCK]

Re: 3.0 omc runs hot

So this impeller is in the lower unit? So could my water pump be bad? Just trying to figure this out before I go buying stuff I dont need.

 

[whywhyzed]

Re: 3.0 omc runs hot

So this impeller is in the lower unit? So could my water pump be bad? Just trying to figure this out before I go buying stuff I dont need.

not in the lower, it's in the bottom of the upper unit on an old OMC. It should be changed every 3 years or so.
Don't worry - buy it, you need it.
Buy the manual, you need that too.
Search "OMC Tilt" on every boating board on the internet - you'll need to fix that that sooner or later too.

P.S. On your OMC stringer drive... DO NOT EVER EVER EVER NEVER EVER NEVER EVER EVER NEVER NEVER NEVER run the engine with the drive tilted. It destroys the ball gears fast.

I see your boat has power trim (the front engine mount electric jack) so learn the difference between tilt and trim. Your drive is like NO OTHER drive system invented in this regard.

Oh, and P.P.S., as an OMC stringer drive owner, you must refer to Mercruiser drives as "Black Anchors" and learn to develop shoulders of a guppy and the skin of an armadillo when conversing with Mercruiser owners about your outdrive.

 

[bruceb58]

Re: 3.0 omc runs hot

...and the oil that goes in that stern drive is a special type. It is called type "C". Don't ever use any other type.

 

[85Searayseville]

Re: 3.0 omc runs hot

I had this problem last summer while at the lake. I replaced the water pump (in the outdrive), checked the t-stat. Turns out my exhaust mani. was clogged, this is what i did. Take off the rubber boot where it connects the 2 pieces of manifold. you'll prob. ahve to buy a new one. Once the boots off disconnect the intake side hose and put your garden hose in it and turn on. Water should come out of that sucker like crazy. If not you got a clog. Proceed to pump water and take a flat head and try to work clogs out of your mani. This fixed my heating problem, might be worth a look .

 

[BIGTUCK]

Re: 3.0 omc runs hot

not in the lower, it's in the bottom of the upper unit on an old OMC. It should be changed every 3 years or so.
Don't worry - buy it, you need it.
Buy the manual, you need that too.
Search "OMC Tilt" on every boating board on the internet - you'll need to fix that that sooner or later too.

P.S. On your OMC stringer drive... DO NOT EVER EVER EVER NEVER EVER NEVER EVER EVER NEVER NEVER NEVER run the engine with the drive tilted. It destroys the ball gears fast.

I see your boat has power trim (the front engine mount electric jack) so learn the difference between tilt and trim. Your drive is like NO OTHER drive system invented in this regard.

Oh, and P.P.S., as an OMC stringer drive owner, you must refer to Mercruiser drives as "Black Anchors" and learn to develop shoulders of a guppy and the skin of an armadillo when conversing with Mercruiser owners about your outdrive.

Thanks for the info. I already have fixed the tilt and know the difference between the tilt and trim. I had to replace the tilt motor and solenoids and yes I figured out the hard way automotive solenoids and marine solenoids are different. Thanks for letting me know not to run it with the drive in the up position. All I need is to get this thing to stop running hot and I am ready to hit the water plus seats.

Another question, has anyone ever heard of Ozark Boat Works because I haven't been able to find much info on them on the net.

Thanks for all the help Iboats, I would have never figured it out without you guys.

 

[BIGTUCK]

Re: 3.0 omc runs hot

well I changed the impeller today, it wasn't near as bad as I thought it would be. holy **** was the water pump assembly a pain to get unstuck.

what is the the purpose of the spring that goes under the exhaust housing cover because it was missing?

I haven't put the unit back on yet, I figured out it is a pain in the butt by your self.

the impeller that came out looked just like the one I put in meaning no broken vanes or what not, so can you tell by looking at an impeller if it is good or not?

 

[whywhyzed]

Re: 3.0 omc runs hot

the impeller that came out looked just like the one I put in meaning no broken vanes or what not, so can you tell by looking at an impeller if it is good or not?

If it looked exactly like the new one, you still have a problem somewhere. If they look good, they are good usually....unless the brass hub in the center has broken loose from the rubber....check that on the old one

I have no idea what that spring does....