87 260 Alpha 1 Issues-Help Please.

[Ryan50]

1st issue-When I purchased the boar last year, the PO explained that it would try to run hot at idle sometimes. The temp did not fluctuate during the 45 minute sea trail. The impeller had not been replaced in 5 years so I figured that was most likely the problem. I rebuilt the water pump in the lower this winter and still have the issue. It only happens when coming down to idle from higher rpms. I can give a few hundred rpms of throttle and it will cool right back down to 165. After that you can pull back to idle and it you can idle in gear for hours and the temp will not raise.

2nd Issue-Boat ran great for hours at all speeds until putting on trailer. While my son was cranking winch, I gave about 2000 rpms to help ease the boat up to the bow stop. While throttling back to neutral to shut it down the engine died and would not restart. I was able to get it started on the hose at home 30 minutes later (some black smoke at start up). I kept it running for several minutes until temp reached normal then throttled back to idle and it shut off and would not restart. I then noticed fuel on the intake manifold leaking from a port on the starboard side of the carb. It also looked like fuel leaking from the carb/intake gasket as well but could not be certain that it was not the same fuel from the leaking port running around the carb gasket at the base. Why would fuel be leaking from the carb even in a flooded condition? I am guessing a carb rebuild is in order. Rochester carb # 260 1347-9662.


Any assistance from you folks is greatly appreciated.

 

[alldodge]

1st issue-When I purchased the boar last year, the PO explained that it would try to run hot at idle sometimes. The temp did not fluctuate during the 45 minute sea trail. The impeller had not been replaced in 5 years so I figured that was most likely the problem. I rebuilt the water pump in the lower this winter and still have the issue. It only happens when coming down to idle from higher rpms. I can give a few hundred rpms of throttle and it will cool right back down to 165. After that you can pull back to idle and it you can idle in gear for hours and the temp will not raise.

2nd Issue-Boat ran great for hours at all speeds until putting on trailer. While my son was cranking winch, I gave about 2000 rpms to help ease the boat up to the bow stop. While throttling back to neutral to shut it down the engine died and would not restart. I was able to get it started on the hose at home 30 minutes later (some black smoke at start up). I kept it running for several minutes until temp reached normal then throttled back to idle and it shut off and would not restart. I then noticed fuel on the intake manifold leaking from a port on the starboard side of the carb. It also looked like fuel leaking from the carb/intake gasket as well but could not be certain that it was not the same fuel from the leaking port running around the carb gasket at the base. Why would fuel be leaking from the carb even in a flooded condition? I am guessing a carb rebuild is in order. Rochester carb # 260 1347-9662.


Any assistance from you folks is greatly appreciated.

Yes look at the carb, but find the clear plastic tubing coming from the fuel pump that goes up to the carb/flame arrestor. If fuel is coming out of it then the fuel pump started leaking. If this isn't the case go pick up a carb kit, probably got some dirt in the needle seat and floods the carb. If you haven't replaced the fuel filter replace it also

Just google carb kit 1347-9662, it will come back with several places

 

[Ryan50]

Thanks AllDodge. The sight tube is dry. I'm going to rebuild the carb. The overheating is stumping me. What could cause an overheat at idle, but only after reducing throttle. It runs cool at all rpms unless you just reduced throttle. If you reduce speed to idle, the temp starts to rise. Then you can add just a touch of throttle and it will cool back down. Once it cools back down, it will stay down even at idle until you speed up and slow down again.

 

[Eric 3.7LX Alpha 1]

Have a read here... it's a newer engine than yours but may offer some ideas:

http://forums.iboats.com/forum/engi...s/383475-mercruiser-5-0-mpi-overheats-at-idle

 

[Ryan50]

Update: Carb is off waiting for rebuild kit. I removed the thermostat housing and found a considerable amount of rust build up, but all passages were open. I cleaned it up a bit. Inside the intake manifold under the thermostat was really rusty. The passages that exit left and right under the thermostat were pretty closed up. I used some wire I had that opened them up a little. I am wondering if there are more blockages in the intake that I cannot reach to clean up. Exhaust manifolds and risers are new. The long block is new, the intake is original. Could rust in the intake manifold be restricting water flow? Is it common to have to replace intake manifolds due to rust? Boat was a freshwater boat until last year, but always flushed well after each use. My other issue is that I do not know the serial number to order parts and gasket (when engine was replaced by previous owner, the mercruiser info was not replaced onto the engine. An old registration shows 2 engine serial numbers: 08641751 (the 08 could be OB) and 08807465 (the 08 could be OB). I figure 1 is prob the engine and 1 the outdrive. Does anyone know how to determine if indeed 1 of these is the engine serial #? She is an 87 260 with rochester q-jet and alpha 1. Any help is greatly appreciated.

 

[Bondo]

Boat was a freshwater boat until last year,

She is an 87 260 with rochester q-jet

Ayuh,.... Boats that run in the brine, do in fact rot out under the t-stat, in the intake manifold,....
They can rot clean through, 'n drop water into the oil from there,....

If ya wanta replace it, the info I quoted should get ya the right intake,....

 

[Ryan50]

Thank you Bondo. I am pretty sure this is my overheat issue. Looking for an intake now.