Troubles a-plenty with 5.0 V8 OMC

[Darcy]

I'm having troubles with my 19' 1985ish sea ray bow rider. It has a cobra I/O with the 5.0 V8. Hrs gauge says around 570 IIRC. More info available if you need... It has quite a few small problems, so help me with what you can please. I'm pretty mechanically inclined, but I haven't spent much time with big block carbed engines. I have the factory manuals. Sorry in advanced for the epic post! I'll give details to help you all diagnose better...

The motor barely starts on one battery. I have to switch to both to get it to crank fast enough to fire the engine. One battery is brand new, and the other is one season old. Admittedly, I haven't put them on the charger, but I have no reason to believe that they are undercharged after a whole day of boating. Volt gauge reads 13ish with engine running, 12 when off. I could be wrong, but it seems to me that the engine isn't turning as fast as it should be. Also, the rhythm is not smooth. Its a steady crank, and then two hard spots, as if two cylinders were harder to tdc than the others. I'm guessing a compression test is in order, but what else should I look for. Is this normal for a big 5.0?

First start of the day always needs quickstart (even in warm weather), and plenty of attention on the throttle for the first few minutes of running to keep if from stalling. Once its warm, idle is fine, and as I recall right in the correct RPM range. I think the choke is working, but I could be looking at the wrong thing on the carb.
I typically have to crank for at the very least 5 seconds every time, even with a hot engine. Often, I am hesitant to shut it down, because its a pain in the butt to get going again sometimes.

Before I purchased the boat, it ran seemingly well. It hit ideal rpm range (per the factory book), and got on plane quickly. After a few summer months, it gradually got fairly severe intermittent power loss. The first problem was the shift switch being misadjusted. I fixed that, but the problem returned, and was more consistent. I couldn't get on plane anymore with even 5 people on board at times. The power loss is less severe after the engine has run for at least 20 minutes. It felt like the engine was bogging down, as if I was overloading it trying to tow something.

Tried to take it out yesterday after 2 months (stored on trailer, ran ok before), and couldn't get it started. cranked and cranked, but rarely a catch. It was about 38F outside, compared to the 60F it was in last time I took it out. Could this be a factor? I did not check for spark, but I think that might be a good place to start looking. Am I on the right track?


Also, the temp gauge hovers around 200-220. I saw this when I was just a guest on the boat, and the guy said no worries. I have since learned that 140 is the ideal range. I will replace the impeller, and the thermostat. Is there anything else I should check out aside from hose damage?

I opened the oil fill cap on top of the valve cover, and what appeared to be steam was coming out. Not a lot like a tea pot, but enough to notice. The oil wasn't milky on the dipstick, so I am fairly certain there is no water in the pan, but this doesn't seem normal. Is it?

I get warm water in the bilge after running. I think I can find the cooling system leak, but I thought I'd mention it.

When turning hard, I get a low clicking noise from the outdrive. I'll pull it to look for rust, but the transom was resealed (previous owner said new bellows too) just before the season. What else should I look for?

Thanks again for anything you can help with. Sorry for the novel!

Darcy

 

[Bondo]

Re: Troubles a-plenty with 5.0 V8 OMC

Ayuh,......

It sounds like that poor little Small block is in Serious need of a Tune-Up,+ Full service.......
The Fuel Filter,+ Carb both sound like they need Changing,+/or Rebuilding.....

And,......
Your Shifting problem is probably a Bad Lower Shift Cable......

 

[Don S]

Re: Troubles a-plenty with 5.0 V8 OMC

It sounds like that poor little Small block is in Serious need of a Tune-Up,+ Full service.......
The Fuel Filter,+ Carb both sound like they need Changing,+/or Rebuilding.....

And,......
Your Shifting problem is probably a Bad Lower Shift Cable......

Along with Bondo information above, Pull the spark plugs and crank the engine and see if any water comes out of any cylinders. If not, do a compression test.
Have you checked the oil level and color???
Cooling system, can we assume you haven't changed the raw water pump impeller on the back of the drive???

 

[Haut Medoc]

Re: Troubles a-plenty with 5.0 V8 OMC

Welcome to iboats......
I would pull the plugs & check for signs of water intrusion.....
It should crank easily without them.....
It sounds like you need a full tune up, but I would try to get it running first......
You probably have a points type system, pulll the cap & look for signs of moisture, corrosion, carbon tracking......
Is this a raw or closed cooling system?....
How old are the manifolds/risers?.....​

 

[blouderback]

Re: Troubles a-plenty with 5.0 V8 OMC

Clicking when turning hard sounds like a gimbal bearing problem.

The hard cranking could be a weak battery, I'd make sure it was charged real good first to eliminate that. Might also be an old a weary starter.

I agree with the others on the fuel filter and carb rebuild, that should help with starting and loss of power.

Running at 200-220 is way too hot. Impeller should be checked to remedy that. Also, warm water in the bilge could mean a leaky riser, manifold, exhaust host, etc. That could also be contributing to the high temp, so track that down too. Check the engine temp with an infrared thermometer ($20 or so from Pep Boys) to verify the gauge is accurate as well.

Steam from the oil fill cap is not out of the ordinary, as long as it's not excessive.

Good Luck!

 

[Gary H NC]

Re: Troubles a-plenty with 5.0 V8 OMC

Running hot,hard cranking and all the other problems sounds like my old 4.3 when the head gaskets were bad due to it being ran hot with a bad impeller.
Just a guess but you have a lot of things to check...

 

[MikDee]

Re: Troubles a-plenty with 5.0 V8 OMC

The motor barely starts on one battery. I have to switch to both to get it to crank fast enough to fire the engine. One battery is brand new, and the other is one season old. Admittedly, I haven't put them on the charger, but I have no reason to believe that they are undercharged after a whole day of boating. Volt gauge reads 13ish with engine running, 12 when off. I could be wrong, but it seems to me that the engine isn't turning as fast as it should be. Also, the rhythm is not smooth. Its a steady crank, and then two hard spots, as if two cylinders were harder to tdc than the others. I'm guessing a compression test is in order, but what else should I look for. Is this normal for a big 5.0?

IMO, Aside from possible water in the cylinders, this sounds like a classic case of too much static timing advance

First start of the day always needs quickstart (even in warm weather), and plenty of attention on the throttle for the first few minutes of running to keep if from stalling. Once its warm, idle is fine, and as I recall right in the correct RPM range. I think the choke is working, but I could be looking at the wrong thing on the carb.
I typically have to crank for at the very least 5 seconds every time, even with a hot engine. Often, I am hesitant to shut it down, because its a pain in the butt to get going again sometimes.

Easy enough to tell if your chokes working, take off the flame arrestor when cold, (choke butterfly should be closed) then when hot, (choke butterfly should be open)

Before I purchased the boat, it ran seemingly well. It hit ideal rpm range (per the factory book), and got on plane quickly. After a few summer months, it gradually got fairly severe intermittent power loss. The first problem was the shift switch being misadjusted. I fixed that, but the problem returned, and was more consistent. I couldn't get on plane anymore with even 5 people on board at times. The power loss is less severe after the engine has run for at least 20 minutes. It felt like the engine was bogging down, as if I was overloading it trying to tow something.

A warmed up engine always runs better then cold.

Tried to take it out yesterday after 2 months (stored on trailer, ran ok before), and couldn't get it started. cranked and cranked, but rarely a catch. It was about 38F outside, compared to the 60F it was in last time I took it out. Could this be a factor? I did not check for spark, but I think that might be a good place to start looking. Am I on the right track?

As Bond-o suggested, a full tune up is in order, do a compression test also, while you have the plugs out, read the plugs, & check for water in the cylinders?

Also, the temp gauge hovers around 200-220. I saw this when I was just a guest on the boat, and the guy said no worries. I have since learned that 140 is the ideal range. I will replace the impeller, and the thermostat. Is there anything else I should check out aside from hose damage?

Way too hot, this is not a car, the stock marine thermostat is 145* your engine might run a bit hotter maybe 160* under load,,, on the muffs, it usually, normally, doesn't even read 145*

I opened the oil fill cap on top of the valve cover, and what appeared to be steam was coming out. Not a lot like a tea pot, but enough to notice. The oil wasn't milky on the dipstick, so I am fairly certain there is no water in the pan, but this doesn't seem normal. Is it?

Running that hot, steam is normal, but keep an eye out for excess moisture in the oil.

I get warm water in the bilge after running. I think I can find the cooling system leak, but I thought I'd mention it.

When turning hard, I get a low clicking noise from the outdrive. I'll pull it to look for rust, but the transom was resealed (previous owner said new bellows too) just before the season. What else should I look for?

Find the source of that leak, and again, the clicking could be too much timing advance, see my first sentence up above.

Thanks again for anything you can help with. Sorry for the novel!

Darcy

 

[Darcy]

Re: Troubles a-plenty with 5.0 V8 OMC

Update:

Did a compression check today per the OMC manual. Open throttle and choke, no plugs in engine. 3 compression cycles each cylinder.

Going around the engine, front to back, the psi was 90, 30,75, 60; and 45, 25, 30, 40

I'm a little worried at these low readings! I did not try putting some oil on the cylinder.

I was cranking with both batteries and a 100A starting charger. Starter still seemed weak. Spun freely with no plugs, but the compression check really slowed down the starter, almost stopped it. Sound like a rebuild canidate, or just get a new one? I'll leave each battery on the charger while I'm at work.

Plugs were all dark brown (almost black), and wet. Seemed to be fuel, but one looked like it had rust on it, that wiped away easily. Gaps were at .040. OMC specs .035

Oil from dipstick looks normal. Some milkshake looking oil in valve covers.

No chance to check the timing yet. Figure I should address the compression good first.

Thanks!

 

[Don S]

Re: Troubles a-plenty with 5.0 V8 OMC

If your compression gauge is accurate, and you were cranking at the proper rpm, your engine is JUNK.
While the starter may be weak, it could also be battery cables, but you have to get it spinning to do an accurate compression test.

 

[MikDee]

Re: Troubles a-plenty with 5.0 V8 OMC

Update:

Did a compression check today per the OMC manual. Open throttle and choke, no plugs in engine. 3 compression cycles each cylinder.

Going around the engine, front to back, the psi was 90, 30,75, 60; and 45, 25, 30, 40

I'm a little worried at these low readings! I did not try putting some oil on the cylinder.

I was cranking with both batteries and a 100A starting charger. Starter still seemed weak. Spun freely with no plugs, but the compression check really slowed down the starter, almost stopped it. Sound like a rebuild canidate, or just get a new one? I'll leave each battery on the charger while I'm at work.

Plugs were all dark brown (almost black), and wet. Seemed to be fuel, but one looked like it had rust on it, that wiped away easily. Gaps were at .040. OMC specs .035

Oil from dipstick looks normal. Some milkshake looking oil in valve covers.

No chance to check the timing yet. Figure I should address the compression good first.

Thanks!

OMG! It's worse then I thought, how can an engine even run with those comp. figures? I think you better make sure your gauge is good, or you're cranking fast enough.

 

[Don S]

Re: Troubles a-plenty with 5.0 V8 OMC

It really sounds like this thing has run for many years with absolutely no maintenance done on it. Is this true????????

 

[Malibud]

Re: Troubles a-plenty with 5.0 V8 OMC

Could it be a bad starter ?

 

[Darcy]

Re: Troubles a-plenty with 5.0 V8 OMC

Could it be a bad starter ?

Update!

Yes, the starter was the beginning of my problems. I replaced it today, and the engine fired right up. Crank speed was much better! Turns out that the + post on the solenoid was loose too!

I also changed out the thermostat. It looked like the one from the factory was still in there! I had to pry it out after scraping away the rotted o-ring. I'm sure that was the source of my hot running issues. Checked the raw impeller, and it looked brand new. I'll still replace it before the season.

When I pulled all of the manifold plugs, no water came out of the rear drains on the exhaust. They were clogged with black rusty/carbon junk! I reamed that out of there, but what else should I look for? Is this going to cause a problem somewhere else in the system, or is this somewhat expected on an older boat? Also, there is a small hairline crack in the starboard exhaust manifold. It isn't flowing water, but the crack was damp. How big of a deal is this?


I'm going to adjust the timing, and the shop manual isn't very detailed. I haven't searched the forum yet, but can you guys point me in the right direction please?

Is all of the water/exhaust supposed to come out of the propeller shaft, or does it also come out below the bellows at the transom? It seemed like most of mine was exiting near the anode right up against the boat. Normal?

Thanks!

 

[Lou C]

Re: Troubles a-plenty with 5.0 V8 OMC

Are you in an area that gets freezing weather, if so the manifolds may be cracked if they did not drain till you dug the crud out. That's a sign of deferred maintenance for sure. So I'd pull those off and check them for sure.
The water exiting under the pivot housing is normal at idle speed.