OMC overheating problem

[matt]

hello,I have a 1974 amc slick craft with a 225 orig omc.I Am having an issue with heating up,just changed the impeller and the thermostat,at idle temp is steady160,but when I give it throttle temp rises right up. fresh water intake hose is even warming up.a mechanic checked it out and believes it is getting to much water in the exhaust and suggest that I change the exhaust manifolds.any suggestions

 

[Chris]

Hi Matt,

Welcome to the forums - nice to have you with us.

I've never heard of that issue.

I wish I could help more with that question, but I'm afraid that one is beyond my backyard mechanic skills.

Maybe one of the other members will have some insight.

-Chris

 

[Fun Times]

hello,I have a 1974 amc slick craft with a 225 orig omc.I Am having an issue with heating up,just changed the impeller and the thermostat,at idle temp is steady160,but when I give it throttle temp rises right up. fresh water intake hose is even warming up.a mechanic checked it out and believes it is getting to much water in the exhaust and suggest that I change the exhaust manifolds.any suggestions

Did you have this problem before the new parts or after?

 

[Fun Times]

[FYI] Also if it is the type of stern drive I think I have read about some place, You might be getting some exhaust blow by in to the water intake system in side the drive, From either from maybe a bad seal or there is a drive style out there that they say you could just add a ton of grease to it and that will stop the exhaust from getting to the water intake system

 

[matt]

I did have this problem before the new part,that is why i started to change obvious parts. I just dont understand what is going on. 1 week before the wife and I took the boat on a 50 mile trip and everything was fine.the day before this all started we were out on our lake erie and 4 to 6 ft waves kicked up and I wasnt sure if something may have let go.Thank for the imput

 

[Fun Times]

I did have this problem before the new part,that is why i started to change obvious parts. I just dont understand what is going on. 1 week before the wife and I took the boat on a 50 mile trip and everything was fine.the day before this all started we were out on our lake erie and 4 to 6 ft waves kicked up and I wasnt sure if something may have let go.Thank for the imput

Well keep us updated on what you find out with your engine, Or if you need any more help we will try to give it if we can. Good luck with it. By the way do you have this kind of drive?

I've got a 1975 stringer and I replaced the impeller without any problems. Actually I had one problem and that was busting off a siezed bolt head, but that's a hazard with wrenching on any older machinery. I was a little apprehensive about doing mine, but it's not that bad of a job. Took me about 3 hours and I pulled the leg right off the boat to do it. One of those 'workmate' style table/vices works great for holding the leg to work on.

Did a compression test on it tonight....

Cyl 1 175psi
Cyl 2 175psi
Cyl 3 176psi
Cyl 4 178psi

Is this normal?
That is basically a NEW engine. Nice.

Try greasing your swivel bearing and go for a run.

Your w/p is prob sucking exhaust gases. The grease will seal it up.

 

[matt]

that does look like it but the boat is not in front of me,Ijust went out and took off the exhaust manifolds and I am going to get new ones from marina,if that doesnt work I dont know.thanks for checking in

 

[Fun Times]

that does look like it but the boat is not in front of me,Ijust went out and took off the exhaust manifolds and I am going to get new ones from marina,if that doesnt work I dont know.thanks for checking in

If that is with in the style drive you have try finding out from the dealer guy's where the fitting is and put a lot of grease in it to see is you get it to run right By doing that. From what you said this makes more sence the the exhaust manifold idea at least to me anyways But I could be wrong, I do not work on OMC. Did you get my PM?

 

[matt]

message I did,I just found a site where a guy had the same problem and he was told to grease the swivel bearing.he did that and he said it worked.maybe I will put the exhaust manifolds back on and try that.

 

[Fun Times]

message I did,I just found a site where a guy had the same problem and he was told to grease the swivel bearing.he did that and he said it worked.maybe I will put the exhaust manifolds back on and try that.

Good luck I think you will be on the right track with that Please let us know what you find out, thank you

 

[matt]

out of ideas,took it to the marina for repairs.thanks boat teck

 

[Fun Times]

out of ideas,took it to the marina for repairs.thanks boat teck

Sorry I couldn't help much, Some are hard to find and others are even harder to find. I hope they test it for you before they give it back to you. It sounds like some shops do and some do not test it out on the lake when they are done with it, From what I have read on the fourms before. Well good luck with it I hope they find it for you.

 

[Fun Times]

I have found some good general info to help every one understand general engine over heat problems out of a mercruiser engine service manual, I hope this info will help some one out some day..

Engine Overheats (Mechanical)
Cause Special Information
Engine RPM below specifications at wideopen-
throttle (engine laboring)
Damaged or wrong propeller; growth on boat
bottom;false bottom full of water
Wrong ignition timing Timing too far advanced or retarded
Sticking distributor advance weights
Spark plug wires crossed (wrong firing order)
Lean fuel mixture Refer to “Carburetor Malfunctions” in this section
Wrong heat range spark plugs
Exhaust restriction
Valve timing off Jumped timing chain, or improperly installed
Blown head gasket(s)
A blown head gasket(s) normally cannot be
detected by a compression check. Normally the
engine will run at normal temperature at low
RPM, but will overheat at speeds above 3000
RPM.​

Engines that are seawater cooled

: Using a​

clear plastic hose, look for air bubbles between​

seawater pump and engine. If there are no

bubbles present, install clear plastic hose

between thermostat housing and manifold(s).If
air bubbles are present at a higher RPM, it is a
good indication there is a blown head gasket.
Insufficient lubrication to moving parts of engine Defective oil pump, plugged oil passage, low oil​

level. ​

IMPORTANT: ​

The first step is to verify if the engine​

is actually overheating or the temperature gauge or​

sender is faulty

Loose or broken drive belt

IMPORTANT: Best way to test gauge or sender is
to replace them.
Seawater shutoff valve partially or fully closed
(if equipped)
Clogged or improperly installed sea strainer
Loose hose connections between seawater
pickup and seawater pump inlet (models with
belt driven seawater pump only)
Pump will suck air. Pump may fail to prime or will
force air bubbles into cooling system.
Seawater inlet hose kinked or collapsed
Seawater pickup clogged
Obstruction on boat bottom causing water
turbulence
Obstruction will be in front of seawater pickup,
causing air bubbles to be forced into cooling
system
Defective thermostat
Exhaust elbow water outlet holes plugged
Insufficient seawater pump operation Worn pump impeller
Obstruction in cooling system such as casting
flash, sand, rust, salt, etc.
Refer to water flow diagram for engine type
being serviced
Engine circulating pump defective
Also refer to “Engine Overheats (Mechanical)”
IMPORTANT: In addition to previous checks,
make the following checks if engine is equipped
with closed cooling.
Low coolant level
Antifreeze not mixed properly Antifreeze should be mixed 50/50 or maximum
60/40 (60% antifreeze, 40% water)
Heat exchanger cores plugged
Water hoses reversed at the water distribution
block​

Refer to water flow diagram in Section 6.
Insufficient Water Flow From Belt Driven Seawater Pump
Cause Special Information
Drive belt Loose, worn or broken
Seawater shutoff valve partially or fully closed
Clogged or improperly installed sea strainer
Loose hose connections between seawater pickup
and seawater pump inlet
Pump will suck air, pump may fail to prime or will
force air bubbles into cooling system
Seawater inlet hose kinked or plugged
Seawater pickup plugged
Obstruction on boat bottom causing water turbulence.
Obstruction will be in front of seawater pickup,
causing air bubbles to be forced into cooling
system​

Faulty seawater pump

 

[matt]

still in the shop,waiting for parts from a vintage parts supplier.marina says whoever worked on the outdrive last did not replace all of the grommets,so they think Im getting exhaust into the water intake system. WELL SEE ABOUT THAT! I will let you know.

 

[matt]

boat teck,well boat is back in the water and everything is good,temp is steady 160 been out 3 times in 4 days,feels good.marina replaced impeller housing,numerious grommets that were some how missing? that was letting the air into the water system,they had the boat for 3 wks and it cost me $800.00.but in my opinion it was worth every penny.just felt like I should let you know,thanks again MATT.

 

[Chris]

Glad to hear you got it fixed up.

Now hopefully you can go do some boatin'.

-Chris