Cooling Issues

[loaderman]

Hi everyone, im new at this posting problems thing, so , here goes.

I have a 1986 Wellcraft Sportsman with a cooling issue. It has a cobra outdrive, and 5.8 mercruiser. I have owned this boat for a few years now and i am now having cooling issues. I first suspected the impeller in the outdrive, but have now discovered another issue to question.

I removed the impeller housing to inspect the impeller (which is intact but needs replaced) and had a brainstorm, what if i put the muffs on to verify flow to the impeller. Well, what i discovered is that behind the housing the passages split, and one was holding water where as the other wasnt.

I turned on the hose to verify flow, and just as i suspected, only the port passage had a flow, the starboard seemed to be clogged.

I pressurized the muffs trying to "make" the flow push out any obstruction, but had no effect. I suspect a blockage. Am i on the right path, and if so, how do i clear the obstruction?

I really need to get this issue resolved seeing that striper fishing is here and i cant troll my downriggers without overheating.

 

[bruceb58]

Re: Cooling Issues

I think you are on a wrong path. Have you put a new impeller in an looked at the water flow at the engine yet?

What was actually happeneing when you were running the engine?

 

[havasuboatman]

Re: Cooling Issues

Are you kidding? Nothing is blocked.
Think about it, that is a pump. If water came out of both passages from the ear muffs how exactly is it a pump?
When the impeller spins, it sucks water into the pump housing thru the port passage and pushes it out thru the starboard which leads to the motor.

 

[loaderman]

Re: Cooling Issues

Actually, im not kidding. It was a serious question. I am by no means framilliar with the workings of an out drive. All my boats until now have been outboards. I have the impeller out and the vanes are intact, however they are cracked and very pliable, so im going to replace the impeller and the thermostat. I feel that it would be a good start, since i have never done it since owning the boat. The boat dosent run constantly hot, it is an issue that varies depending on throttle position, so im thinking a possible thermostat issue as well as an impeller issue. No blockages between motor and outdrive, it just seems that sometimes it cools better at low rpm range than at the high range.

 

[loaderman]

Re: Cooling Issues

Also, sometimes it happens at low rpm range after running at speed for a few mins. I have experienced it at various rpm ranges. When i throttle up in neutral to increase the water flow, it will cool down. This is driving me crazy. Especially since i moved my houseboat to a mooring line and need my Wellcraft to get to my houseboat.

 

[180shabah]

Re: Cooling Issues

Have you checked the manifolds and elbows for partial blockage?

FWIW - that 5.8 is not a mercruiser.

 

[loaderman]

Re: Cooling Issues

5.7, and it is either a mercruiser or has the wrong stickers on it. And i am pretty sure manifolds are clear, im pretty sure that its an impeller issue, or a thermostat issue. Whats the best way to verify flow to all places. The boat is trailered all winter and through the week until the weekends, this has been a slow developing issue that began at the end of last summer, and it hasnt been an issue thats constant till now.

 

[180shabah]

Re: Cooling Issues

5.7 sounds better.

Not knowing any history, other than the engine has been replaced at some point. I would start at the seawater pump and go through each hose and component all the way to the exit in the elbows.

If you suspect there is debris in the caught in the thermostat, pull it apart and look. "pretty sure manifolds are clear" doesn't sound very convincing. Are they new? Have you pulled them off for inspection? Were they replaced with the engine, or are they the originals (25 years old now)? Do you have a power steering cooler? they can catch debris also.

 

[loaderman]

Re: Cooling Issues

Why do you feel that the engine has been replaced, according to all my research and paperwork on the boat, it is the stock 5.7L v8. I havent pulled the manifolds yet, rain set in on me yesterday as i began working on it. The impeller is in pretty poor condition, how much of an issue could that cause? I am still confused with why you think the engine has been replaced.

I think i confused every one by saying 5.8... My Bronco is a 5.8, my boat is a 5.7 . Sorry for the confusion, easily mixed up when im checking on parts for both motors

 

[bruceb58]

Re: Cooling Issues

Why do you feel that the engine has been replaced, according to all my research and paperwork on the boat, it is the stock 5.7L v8.

For the same reason you started your thread with a Cobra drive and a Mercruiser engine. Those are two seperate companies. The Cobra is made by OMC.

 

[180shabah]

Re: Cooling Issues

I think i confused every one by saying 5.8... My Bronco is a 5.8, my boat is a 5.7 . Sorry for the confusion, easily mixed up when im checking on parts for both motors

5.8 = ford 351
5.7 = chevy 350

While OMC used both ford and chevy engines right up to the end, Mercruiser hasn't used ford since the late 70's. We just really need to know what you have to be of any real assistance.

 

[loaderman]

Re: Cooling Issues

Once again, sorry for the confusion, my motor in the boat is a 5.7L, chevrolet 350. Which i am very framilliar with the motor, just not the outdrive. I will make an attempt after work to check the flow through the rest of the engine, after i install a new thermostat and the new impeller. I figure that the easiest and most accesssble things first, because after all, what can it hurt to know that i have the new parts installed . Then i will go from there and check the flow throughout the rest of the engine.

 

[180shabah]

Re: Cooling Issues

I agree a new impeller and t-stat are good. And even if they are not the cause of this problem, you will have eliminated the next problem. Systematically follow the waterflow and you will find the problem.

 

[loaderman]

Re: Cooling Issues

One last question for a few. Is the t-stat a common, chevrolet t-stat, or is it some odd-ball marine thing that is gonna cost an arm and leg just because it goes in a boat motor.

 

[bruceb58]

Re: Cooling Issues

It is different becuase the thermostat housing is different.

 

[liquidlew]

Re: Cooling Issues

After you check your flow and find that it's good but still have cooling problem, check your engine timing, maje sure it is set to the correct specs for your engine, and a tune up would be a good thing too!

 

[loaderman]

Re: Cooling Issues

The tune up is recent, only 20 hours or so of run time on new plugs, and oil change. Only 1 or 2 hours on new fuel filter. At the end of last season (around labor day) i put a new coil and points, cap and rotor button in. Havent changed plug wires yet, but they ohms check as good, so i felt there was no need.

 

[liquidlew]

Re: Cooling Issues

Well I mentioned the timing because after I did a full tune up, new water pump (engine and lower unit), new manifolds, risers, and thermostat, had excellent flow but temp was still climbing at idle on the muffs. Decided to recheck the timing and it was off because some chucklehead (me:redface didn't tighten the dist. hold down bolt enough. It was off just enough for it to go hot but still idle smooth.

 

[loaderman]

Re: Cooling Issues

Well i would like to thank EVERYONE for their input on my problem. I just now came in from working on my boat (9 p.m.) and am proud to announce that i think i have the issue resolved. I replaced the impeller, and the thermostat (which was very rusty) and ran it on muffs for about 30 mins. Temp didnt rise above 120 deg. Usually it would have went to 200 plus in that time at idle. Im not sure which one was the fix, but they both were in desperate need of replacing. The new impeller actually was drawing so hard at 1500 rpm's that it was collapsing my water hose.


SO I SAY AGAIN, THANK YOU TO ALL FOR YOUR HELP

 

[cr2k]

Re: Cooling Issues

"I have the impeller out and the vanes are intact, however they are cracked and very pliable"

This, plus the fact that you say you have never changed it tell us that is your problem.

Impellers should be changed every other year. Period. Used or not.

I think you will find much better cooling after you change it.