Seawater pump 7.4 bravo1

[Handsome Transom]

I will I have already had the one lower off and was able to keep up with my onboard bilge pumps without bagging I am hopeful that I can slow it enough to get the shutters changed I'll for sure fill in on this when I do it tomorrow or Tuesday so someone in the future can benefit from my experience good or otherwise.

So I did the port side exhaust tubes and shutter valve yesterday and it went well .fitting the shutters is the most challenging part . I didnt bag the drive . Onçe the lower tube is off the fun starts. Pried the old shutter out while rinsing the bilge with plenty of water .pumps start. Once it was out i jammed on the lower tube to stem the flow and worked from inside it to fit the new shutter. All together again with new riser gaskets and everything is great

 

[Handsome Transom]

Didn't think the top of the Y pipes were so close to water line but in that event, don't think a bag over the drive is going to help much unless it can somehow cover the little exh ports on the transom plate too. Let us know how you make out

Yes they are about 1/4 " below the water level .port side is done and went well

 

[Handsome Transom]

Since you don’t know the maintenance history I would do C. As far as waiting, hard call, it’s working now but you don’t know how old the impeller is. First sign of a failing water pump is risers getting hot - should be able to lay your hand on them if too hot to do that you are starting to have problems. If risers are cool I might wait.

So the exhaust tubes are done along with new shutters . Also new heater hoses to the new water heater and going to do the other cooling hoses today as soon as they arrive. I believe they are original and time to replace on a 30 year old boat I am surprised they lasted and although really old still not leaking . I pulled the plugs in the manifold to çheck water flow and there is plenty I am c concerned with scale rust and residue in the block and wondering if I should use ridlyme or vinegar and given the block an internal soak and flush. My concern is because my port side riser is hotter than the starboard not lots but definitely noticeably.

 

[BillK2632]

It's normal for one riser to be hotter than the other, that is due to how the water flows through the system. I have had several different Mercruiser engines and they all behave that way. The point is, even on the hotter one it should not be too hot to lay your hand on. It's been awhile since I've done it so don't hold me to my numbers, but if you put a heat gun on it should be somewhere between 100-140deg - there was about a 20deg difference between the cool and warm one. On my 4.3, one riser at idle is "cool" and the other is "warm" I could lay my hand on them all day. After running and coming off plane if I checked one would be "warm" and the other would be "very warm" but still able to leave my hand on them.

As far as rust/scale in the engine water passages - Your in Canada, so I am assuming freshwater? If the boat has been in freshwater and with the short season up north, you are not likely to ever have issues with the raw water system - engine block, risers or manifolds. I know our salt water friends are constantly working on this about every 5-7yrs, but I have boated in freshwater my whole life, we have had all kinds of boats and I don't recall replacing an exhaust manifold or riser ever. My current boat is a 1999, so almost 20yrs old - I have replaced the raw waterpump numerous times and the circulating pump once, but would not even think about pulling a manifold or riser - at least not out of concern of rust/scale buildup. If you are pulling these parts it's because of freeze damage or in the rare case a manufacturing defect.

If you are truly worried, go ahead and do a flush it can't hurt, also pull the thermostat housing and have a look that will give you and idea of the condition of the water passages and the risers. If you start trying to pull manifolds and risers on a 30yr old motor, something is likely to break, so be ready to just replace them.

 

[Handsome Transom]

It's normal for one riser to be hotter than the other, that is due to how the water flows through the system. I have had several different Mercruiser engines and they all behave that way. The point is, even on the hotter one it should not be too hot to lay your hand on. It's been awhile since I've done it so don't hold me to my numbers, but if you put a heat gun on it should be somewhere between 100-140deg - there was about a 20deg difference between the cool and warm one. On my 4.3, one riser at idle is "cool" and the other is "warm" I could lay my hand on them all day. After running and coming off plane if I checked one would be "warm" and the other would be "very warm" but still able to leave my hand on them.

As far as rust/scale in the engine water passages - Your in Canada, so I am assuming freshwater? If the boat has been in freshwater and with the short season up north, you are not likely to ever have issues with the raw water system - engine block, risers or manifolds. I know our salt water friends are constantly working on this about every 5-7yrs, but I have boated in freshwater my whole life, we have had all kinds of boats and I don't recall replacing an exhaust manifold or riser ever. My current boat is a 1999, so almost 20yrs old - I have replaced the raw waterpump numerous times and the circulating pump once, but would not even think about pulling a manifold or riser - at least not out of concern of rust/scale buildup. If you are pulling these parts it's because of freeze damage or in the rare case a manufacturing defect.

If you are truly worried, go ahead and do a flush it can't hurt, also pull the thermostat housing and have a look that will give you and idea of the condition of the water passages and the risers. If you start trying to pull manifolds and risers on a 30yr old motor, something is likely to break, so be ready to just replace them.

Ok good news in the temp difference . Btw we do have oceans here too but you're correct I boat in Georgian bay . I had my risers off when I did the exhaust bellows or tubes and shutters they are not bad at all minor scale.the manifolds look good from visual inspection with the risers removed.what I noticed was quite a bit of scale in the hoses i am replacing as well as plenty of rust on the t stat housing in fact one of the nipples that feeds the lower hose leading to the bottom of the manifold is actually deteriorated at it's lip. My biggest concern is the small passages in the block. I think ill go for it with an acidic solution . Luckily my boats motor is extremely clean and I have not had any issues getting large fasteners loose but I understand about breaking old stuff for certain . Thanks so much for your experienced input
Davr

 

[Handsome Transom]

It's normal for one riser to be hotter than the other, that is due to how the water flows through the system. I have had several different Mercruiser engines and they all behave that way. The point is, even on the hotter one it should not be too hot to lay your hand on. It's been awhile since I've done it so don't hold me to my numbers, but if you put a heat gun on it should be somewhere between 100-140deg - there was about a 20deg difference between the cool and warm one. On my 4.3, one riser at idle is "cool" and the other is "warm" I could lay my hand on them all day. After running and coming off plane if I checked one would be "warm" and the other would be "very warm" but still able to leave my hand on them.

As far as rust/scale in the engine water passages - Your in Canada, so I am assuming freshwater? If the boat has been in freshwater and with the short season up north, you are not likely to ever have issues with the raw water system - engine block, risers or manifolds. I know our salt water friends are constantly working on this about every 5-7yrs, but I have boated in freshwater my whole life, we have had all kinds of boats and I don't recall replacing an exhaust manifold or riser ever. My current boat is a 1999, so almost 20yrs old - I have replaced the raw waterpump numerous times and the circulating pump once, but would not even think about pulling a manifold or riser - at least not out of concern of rust/scale buildup. If you are pulling these parts it's because of freeze damage or in the rare case a manufacturing defect.

If you are truly worried, go ahead and do a flush it can't hurt, also pull the thermostat housing and have a look that will give you and idea of the condition of the water passages and the risers. If you start trying to pull manifolds and risers on a 30yr old motor, something is likely to break, so be ready to just replace them.

So I installed all new hoses on my engine and with that done my portside riser is noticeably cooler .almost can't tell if it's different than the starboard side now