running hot

[94proline2550]

I have a 94 Mercruiser/Alpha One Gen II FWC 4.3 vortec. I change the impeller and change the drive oil every new season. Took the boat out for a burn Sunday and it was running up to 180 degrees at 3000 RPM, cooled to 150 below 2000 RPM<br />Over 3000 it'll begin to go over 180. Changed the the thermostat with a new 142 degree. Thinkin' it may be a clogged heat exchanger. Whadda ya think?

 

[Don S]

Re: running hot

Could be the exhaust risers or manifolds are getting plugged up. IF they are original, they are due to be changed at 12 years old, if you boat in salt water, they are WAY overdue. When they start plugging up, they reduce the amount of cooling water going thru the heat exchanger.

 

[Bt Doctur]

Re: running hot

base gasket under the water pump base could be sucking hot exaust but like Don says manifolds and or risers.10 years is a lot in salt water.

 

[Haut Medoc]

Re: running hot

Welcome to iboats I used to live in Toms River, so I had to reply...<br />Pull the end caps & look for obstructions....<br />Don S. is most likely correct however....<br />The dumps in the risers are probably clogged with scale reducing water flow...<br />You should replace the risers, possibly the manifolds, before they fail & leak water into the cylinders....<br />I'm assuming that the manifolds are on the FWC side of the system, examine the mating surfaces on the manifolds very closely, if they even look questionable replace them, esp. since you are in salt (even in the Manasquan River)....<br />It probably wouldn't kill ya to get the exchanger boiled out at a radiator shop & change the coolant with 50%-50% anti-freeze/distilled water....JK

 

[94proline2550]

Re: running hot

New risers and checked the manifolds with the new engines last season. I did put riser spacers in though. When I did, I replaced the shutters with the new style rubber flappers. With the longer exhaust "wye" to riser elbow hoses, I didn't like the way they were sitting. Maybe one or both are binding inside. Is it possible that the engine would run so well and still have an exhaust/water restriction?

 

[Don S]

Re: running hot

So, you're saying this problem started AFTER you installed the extensions? Are your manifolds FWC? Are you sure you have the water plumbed to the risers and extensions properly? How about the type gaskets used?<br />Is this Merc manifolds/extensions/risers or aftermarket?

 

[94proline2550]

Re: running hot

I have twin engines and both aree plumbed with the cooling water going to the spacers. Gaskets are Quicksilver, one has four open slots, the other blocks off the connection between the FWC manifolds and the risers. The second engine runns wide open without a problem.

 

[Don S]

Re: running hot

Time to start looking for things that can resttrict water flow between the pump and the exhaust.The hose between the pivot housing and the transom shield. With age, they kink instead of bend. Or the elbow that goes through the transom sheild could be partially clogged.<br />Check the powersteering cooler, it could have something in it. Did you remove the end caps on the heat exchanger and look for blockages?

 

[Bt Doctur]

Re: running hot

prior to mounting the drive do you pre-lube the impellers.usually to mount a merc you need to be in fwd and turn the prop counterclockwise to line up the shafting.this turns the impeller backwards. if the impeller was dry could the vanes have reversed themselves and now have poor flow.

 

[I/O WALDO]

Re: running hot

That rubber seal on the shaft above the impeller housing HAS to be correctly spaced to prevent air intrusion into the pump.(only gen 2)

 

[Don S]

Re: running hot

BT makes a good point about the Gen II pumps. One thing about them, if the vanes are backwards when the pump is put together, they will NOT turn around when run the other direction. They must be installed the proper direction.

 

[94proline2550]

Re: running hot

We have a nasty day here today in NJ. Gonna pull the raw water feed hose off and direct it to a bucket then run the engine. If the flow is good, I;m going to switch to watching the outflow just long enough to determine flow before the exhaust sees too much heat. That should tell me if the flow is bad coming in or through the exchanger. If both turnout to be good then it'll be drive impeller checking time. I'm sure I replaced it in the right direction, that's why I suspect the exchanger. Thanks so far let you know what happens.

 

[94proline2550]

Re: running hot

Kay, pulled the end caps off the exchanger and saw nothing but daylight from one end to the other. Pulled the elbows off and verified the shutters were there and functioning. Pulled the hose from the transom fitting and the bottom of the exchanger and was able to blow though the hose with no backpressure. That leaves one thing, the impeller or the pump housing. Gonna pull the big money-pit this weekend and change both out. Back after the trial to say what it was.

 

[Bt Doctur]

Re: running hot

when you drop the units, before you remove anything, put muffs on the lowers and see if there is any leakage from the pump area.

 

[94proline2550]

Re: running hot

Good advise, but I'm going to be doing it right at the ramp parking lot. Too big a beast to go too far with it.

 

[Bt Doctur]

Re: running hot

what ramp?<br />leave a number at EJDSR251@aol.com