Mercruiser Risers

[paultallett]

Hi,

I'm off for a few days on the boat and I've noticed for a while that I've got one manifold running warmer that the other on my Mag 350. I've armed myself with new gaskets, workshop manual etc.... and thought if I get a days bad weather I'd pop them off and see if there is some corrosion / blockage inside.

Has any body got some wise words or tips for me on doing the job?? Anything that makes the job easier will be greatfully recieved.

regards Paul.

 

[carlton]

How long have the manifolds and risers been on? Has this been in fresh or salt water? Is the temp. gauge reading normal?

 

[paultallett]

Morning,

Engine is 5 years old and has been used in mainly salt water. The temp gauge is absolutley normal yet the right manifold (when looking towards the stern from the helm) is running warmer, it's not glowing red or anything, it just is warmer to the touch when the engine is running.

Regards Paul.

 

[lovezoo]

It is normal for one manifold to be slightly warmer than the other, due to the way the water flows. If you are planning to remove the manifolds themselves, be careful as they are quite heavy. Also when they are off, it may be worth taking advantage of the extra room you have to do things like changing the spark plugs, checking the starter etc.

 

[davedpc]

I find one of those hand held lazer temp. meters to be handy. You will be able to check for hot spots and compare one engine to the other before going to the trouble of removing the manifold. They are so sensitive they can even tell if a spark plug is duff by the temp. difference to the others with the engine running.

 

[spannerman]

Remember to open the drain plug or remove the hose under the manifold first to drain them before you remove the risers or you will get seawater in the cylinders when you split the riser from the manifold.

 

[paultallett]

Remember to open the drain plug or remove the hose under the manifold first to drain them before you remove the risers or you will get seawater in the cylinders when you split the riser from the manifold.

Thanks for that, I had planned to drain the whole engine off, is it better to do this or just drain the one particular manifold / riser?

Thanks.

 

[volvopaul]

The last pair I had to look at , when the water hose was removed I could not even blow air down the hose they were that bad, removed manifold and immersed them in a descaler to unblock.

 

[spannerman]

You can just drain the manifolds, but if you remove the drain plugs in the side of the block at least there is no possiibility of an accident, you may have to stick a screwdriver in to get it to drain after you have taken the plug out as its where all the rust and crud collects in the bottom of the block

 

[paultallett]

Brill,

Thats just the kind of info I was looking for..... keep the tips coming!! I had planned to rod the risers out with gun brushes, what descaler would you recommend for the manifolds??

Thanks.

 

[volvopaul]

Rydelime descaler buy it from RK marine or motortech.

 

[tinkicker0]

Morning,

Engine is 5 years old and has been used in mainly salt water. The temp gauge is absolutley normal yet the right manifold (when looking towards the stern from the helm) is running warmer, it's not glowing red or anything, it just is warmer to the touch when the engine is running.

Regards Paul.

Time the manifolds were changed then.

 

[paultallett]

Time the manifolds were changed then.

Thats what I was thinking, I just wanted to take a look to make sure that corrosion was the reason before ordering the parts.

Thanks.

 

[AndieMac]

We have a local service agent that always sandblasts the risors and manifolds when they get to a certain age, as part of his maintenance program. He says if they can't take the blasting, they shouldn't be put back on.

 

[tinkicker0]

Thats what I was thinking, I just wanted to take a look to make sure that corrosion was the reason before ordering the parts.

Thanks.

Lifed components.

General rule of thumb for allowing a reasonable margin for engine safety and getting reasonable value for money is:

Salt water - change every 3 years.

Fresh water - Change every 9 years.

This is what the Yanks advocate anyway. Anything over those times and you are on borrowed time, although it depends how you use the boat I suppose.

 

[paultallett]

One more question I guess for Spannerman or Volvo Paul, my workshop manual states 'to use Loctite 510 on the 2 gaskets on the risers as your new gaskets will probably not look like the replacement ones'. I've asked my gasket supplier if I should install the gaskets dry, they said yes but said some engineers do use a sealant. Whats your opions on these gaskets, sealant or not??

Regards Paul.