Impeller housing overheating

[DGMan80]

Took it out again today with the whole family. Went out great, got on the island and hung for about 4 hours, loaded back up to head out and after about two minutes boat died again. Would not restart. Just clicked like the starter was trying but nothing. Gave it a few minutes and it cranked bit wouldn't fire. Ran the kicker back to the marina took about an hour but we got her back. The lady last thing I can think that I haven't looked at would be the fuel line. I'm going to pull every filter in the line and replace as this is the only thing I haven't touched since getting it and honestly probably the first thing with the fuel being older. Any other things I should look at?

 

[Lou C]

Remove the spark plugs and check for water in the cyls. You want to make sure the non cranking issue is not hydrolock. Then take off the flame arrestor and pump the throttle while looking down the carb Venturi; do you see a good squirt of gas? If so lack of gas is not likely your problem. If this is the case you need to go back over all the connections in the starting system starting with the battery cables and terminals. If you have wing nuts holding on your battery cables to the battery get rid of them and use locking nuts or bolt on marine quality clamps to the terminals instead.

 

[Lou C]

PS also these OMCs use an assist solenoid between the ignition switch and the starter. On mine it is mounted with the trim relays (old style large relays). I had a similar problem about 12 or so years ago and it was corrosion on the terminals. Cleaned it all up and it was fine. So don’t forget to check that

 

[DGMan80]

Remove the spark plugs and check for water in the cyls. You want to make sure the non cranking issue is not hydrolock. Then take off the flame arrestor and pump the throttle while looking down the carb Venturi; do you see a good squirt of gas? If so lack of gas is not likely your problem. If this is the case you need to go back over all the connections in the starting system starting with the battery cables and terminals. If you have wing nuts holding on your battery cables to the battery get rid of them and use locking nuts or bolt on marine quality clamps to the terminals instead.

I'm fearing hydrolock Lou, the way it won't crank at all immediately after dying, but then cranking after letting it sit? Each crank getting harder to turn it would seem. Then by the time I get it home 45 minutes later it fires right up on the muffs. I'll pull the spark arrestor off and take a look.

 

[DGMan80]

PS also these OMCs use an assist solenoid between the ignition switch and the starter. On mine it is mounted with the trim relays (old style large relays). I had a similar problem about 12 or so years ago and it was corrosion on the terminals. Cleaned it all up and it was fine. So don’t forget to check that

I'll check the solenoid, this boat when I got it had a loose connection at the trim solenoid. I'm pretty sure I saw another one there.

 

[Lou C]

There are 2 trim relays (1 up & 1 down) and one assist relay. The up will have a blue wire on it, the down has a green wire on it and the assist will have a yellow/red wire. Depending on how the engine cover is designed water can drip back there from rain and cause corrosion...might as well clean em all up.

 

[DGMan80]

Ended up being the same issue, made it out no problem. Anchored up spent 4 hours on the island, loaded up and left. Less than two minutes into the trip back the engine quit. Came in on the kicker again. Everything that happened before, happened again. Got it home and it starts right up. Took it out last weekend to try and replicate. It did! This time im ready with tools in hand. Pulled spark arrestor it's getting fuel. Started pulling plugs. Starboard side looked good. Pulled the #1 port side completely burned up. Pulled #3 port side it's even worse. #5 the ceramic housing cracked while removing but the plug looked ok on the inside. What brand would anyone recommend? I've always used champion, but at this point maybe reconsidering? Anyways, This leads me to believe the port side exhaust manifold it's clogged causing it to run hot. And my temp sensor is no good. I pulled all the drains and ran the hose to it. Fired it up and sure enough nothings coming from the port side manifold. I tried pushing some compressed air through the inlet side, no luck. Went up from the drain, bingo, blew out nasty rusty water. Hooked it back up and ran it for fifteen minutes. At this point I'm seeing that my temp gauge isn't working at all. Everything appears to be flowing though. I tested the sensor, is indeed bad. When I ground the wire it pegs the gauge. Pulled the sensor. I just need to get my hands on another sensor to ensure my temps are dialed in. Anyone know a part number on that sensor? I googled it and everything is showing the part with a 3/8 opening I'm fairly certain it's much larger. (Came off with a 23mm socket!) Lou im definitely looking into a complete exhaust conversion after seeing the condition of those manifolds! At this point I just want to ensure that everything else is in working order, run it through the paces and then get the exhaust parts orders and swapped over. Will I need to pull the motor to do that conversion? It didn't appear I had to, but you would be the expert.

 

[DGMan80]

I'll check the solenoid, this boat when I got it had a loose connection at the trim solenoid. I'm pretty sure I saw another one there.

The solenoid was good however coming from the solenoid going to the starter was a fused line. It is an older glass fused line and when I wiggled the line it was causing it to cutout. It was slightly corroded inside there. I cut it out and replaced it with a large spade fuse.. the cranking was solid however if my engine is overheating I think it may be soft seizing due to heat?

 

[Lou C]

You gotta get the temp gauge working but for now get an IR temp gun and use that to measure temps. Check:
Intake manifold right under stat housing, should be about 10-15 degrees below the rating of the thermostat (standard is 160).
Top of exhaust manifolds (elbow section)
Mine were usually about 90-100 at idle and would get up to 135 after coming off plane but would cool down in about 5 min of idling. Engine temps on gauge 160-175.

Those plugs are trashed. I would check the base timing and total timing advance to make sure it’s not too far advanced. Base is 6*, max centrifugal advance is 12* for a total of 18* at approx 3200-3500 rpm. From my OMC manual. Use AC Delco Marine MR43T plugs.
About the manifolds if they are running hot remove them and make sure the 4 outlets are not blocked. Just pick up a set of manifold to block gaskets. To remove you need to slide the rubber exhaust hoses down the Y pipe first. Then the manifolds will slide right off the studs.
What I used to do was to spray silicone spray on the Y pipe below the rubber hoses. Then get a really thin screwdriver and slide it up between the hose and the Y pipe, to work loose the rubber hose...they get baked on from heat. Then slide the hose down. If you don't do this first the manifolds will not come off. Once you get the manifolds off you can clear out the 4 outlets and hook the hose fitting up to a water hose and test them for flow.
Here's a couple of pix, you can see how one outlet on the one on the right it totally plugged with rust. Last pic is the install of the 2 piece OMC/Volvo system, see how much bigger the water passages are.

 

[alldodge]

Nothing wrong with Champion, took at set out of my 20 year old Rinker and they where still doing fine. Did install MR43T because I got a deal one about 50 of them some time ago

Any plug will do what yours did when they get that hot.

 

[DGMan80]

Thanks guys for the feedback, do you think that the lack of flow would cause the engine to seize and this happen to the plugs? I'm assuming this is why when it dies it acts like it's seized until it cools down. It would also explain why it cranks like a dead battery until it cools down enough to crank normal again. this is my second boat the first one had a two stroke outboard, and I've heard champion is solid so that's what I've put in them. the ceramic housings cracking on two of the plugs makes me reconsider. But honestly I'm sure this would have happened no matter the brand. Does anybody have a p/n for that sensor? I've checked everywhere local and every one is pulling out 3/8 thread sensors. This one is 1/2 inch. Lou is there website you recommend that I can get the entire two piece assembly for both sides? I'll be able to get my hands on an ir temp gun next weekend I think If I can find one this weekend for a reasonable price ill try and pick one up. Once again thank you for the feedback! You guys are super helpful.

 

[alldodge]

every one is pulling out 3/8 thread sensors. This one is 1/2 inch

Are you talking NPT or SAE?
A 3/8 NPT means the ID of the hole is 3/8 which makes the threads .675 which is slightly larger then 1/2

 

[DGMan80]

Are you talking NPT or SAE?
A 3/8 NPT means the ID of the hole is 3/8 which makes the threads .675 which is slightly larger then 1/2

I'm an idiot well off to try and see if they match I was scared to order one online.

 

[alldodge]

I'm an idiot well off to try and see if they match I was scared to order one online.

Been there done that my self many times

 

[DGMan80]

Sourced it locally, turned out to be the 1/2" thread. PN is TS26631 got it installed and fired up the motor on the hose. Temp never went above 145 which I think would be correct with a 140° thermostat in there. I let it idle for about ten to fifteen minutes could feel the water pump hose warm up. The exhaust manifolds were not very warm yet I'm guessing I need to get it in the water and run it under load. Oil pressure was good. It runs about 40 psi at idle. The million dollar question is this, if my exhaust manifolds are not running effectively my temp will indicate it correct ?

 

[Lou C]

In most cases yes especially when you put a load on the engine. However as I said these OE OMC one piece manifolds are somewhat prone to clogging of the outlets because they are on the small side as you can see by the pix I posted. Running on the water hose is not a test of this you need to run the engine up on plane and check temps at the intake under the stat housing and on the manifolds.

 

[DGMan80]

That'll be the next thing I do. Almost took it out today after getting everything put back together. Weather was awful and I was soaked after installation. Hopefully I can sneak out after work one day this week. Im going to pickup a cordless IR temp gun and I'll check the temps. A question on those two piece manifolds, do you replace the risers as well ? Or is it just the exhaust manifolds? Thanks again for the feedback.

 

[Lou C]

the two piece conversion is a manifold+elbow+90* exhaust pipe & hoses....pretty much the standard Volvo Penta set up used from 1994 all the way up till yjey dded cat converters. It will fit the Cobra perfectly. Firts 2 pics are my conversion last pic shows how it looks from the back side. I used Barr aftermarket for the manifolds and elbows and Volvo OE for the rest....

 

[DGMan80]

Update #400 it's been an eventful evening. Got the boat in the water fired right up idled for 5 minutes and pulled off the dock. Ran in gear at idle for a minute then ran the throttle up. As I crossed about 2k rpms the motor started acting up. Kinda bucking a bit. I pulled power and it died. It didn't seem to matter what rpms I ran it at it high or low would sometimes sound like clunking at the outside and then it would die. It fired back up every time. One thing I did notice was that in neutral it wouldn't like go over about 3k rpms however just listening I feel like it was much higher than the tach showed. I'm going to run it on a timing light tomorrow. My first thought was a u-joint or the gimbal bearing as of these were not dialed in it may cause this?? Get it back to the dock cannot get the outdrive up. Solenoid clicks but will not engage. Tried everything, ended up going straight to the plug with jumper wires to the battery. Finally got it raised. Back the trailer down pull it on the trailer. Goto pull up the ramp snap! The strap shreds and the boat rolls of the back of the trailer. Luckily it's still in 5 feet of water and its sitting at about a 45° angle sitting on the back roller and resting on the bottom of the outdrive. I quickly tied the end of the strap to the hook and winched it up. Seemed like too much weight to leverage I ended up having to back it up about six inches. It scraped slightly I the outside then floated back into the trailer. Absolutely insane afternoon. Checked the bottom of the boat fairly well to ensure no bowing punctures or unusual marks. Couldn't find any. I definitely learned my lesson to hook the secondary safety chain immediately before pulling out. I typically would do that after pulling out and securing everything. Back to the boat I was planning on pulling the outdrive off and checking everything between the motor and the outdrive. Any other ideas? On a positive note the engine runs at 140° it's got a 140° thermostat in it. Manifolds are all running cool as well. Put the ir temp sensor on everything today engine it was running nothing was too hot anywhere.

 

[Lou C]

Ok you have some symptoms time to put them together and make sense of what is happening. Burnt up spark plugs, and an engine that won't take a load, sounds like very lean fuel mix. First thing go back to basics. You may have a rusted and or sticking anti siphon valve, that would explain the unwillinglness to rev under load. Also check the fuel tank vent. I had the anti siphon valve problem on my boat years back.
What carb do you have? Rochester? 2bbl or 4bbl? Might be time for a carb rebuild.
Also, ignition system....OE is a Prestolite points distributor, unless someone changed it out. When was the last time the points were checked, gap & dwell? I check mine every season, usually replace them every 5 seasons or so. Dwell should be 39* + or - 2*.
Cap and rotor? they don't last forever. If you can get a hold of an advance timing light check base timing and total timing advance with the boat in the water (@ 3200-3500 rpm). Base should be 6*BTDC. Total, is 18* (12* centrifugal advance + 6* base) yes that seems low compared to the V8s but that's what is in the OMC shop manual. If the distributor and carb have not been maintained it will never run well. Don't forget the anti siphon valve. That had me scratching my head because back then I was not familiar with marine fuel systems.