fred

I am changing my old style log type with rear riser exhaust to new style center riser, my existing themostat housing and cap only have 2 outlets (1 for each riser per motor) the new exhaust requires 4 (2 for ea. riser) does anyone have 2 housings or caps with 4 outlets on them?...or is there another way I should do this? Thanks Fred

dyno

Fred call Jim Valeco he always has a bunch of take off stuff....

fred

Good idea Don, I'll do that, Thanks Fred

ursus

you do not need to change thremostat housings. You can use the 2 out let thermostat, just plug the hole in the riser with a screw in brass plug and use the riser gaskets that allow water to flow in all 4 passages versus the gasket that has water flowing in only 2 passages. This is what Merc does on newer engines. The 2 passage gasket has two 1" or so long passages and two 3/16" holes. The gasket you need has four 1" long holes one on each side. Merc part #27-863726 is the 4 hole gasket #27-863724 is the 2.

fred

Thanks ursus, I'll look into the gaskets....sure would make the change over much easier without having to change housings and all that....Fred

ursus

P.S. make sure to get the newer style riser gaskets, these look silverish, versus the older style with a red or orange fire ring/strip

MrCIG

Fred,
Ursus is correct.
I did that on my Formula and had over 300 hours and no problems. The hose goes in the bottom of the manifold and new riser gaskets and you done.

Mark

fred

Mark, did you plug the fitting on the riser and just use the one on the bottom of the manifold to feed the hose to?.....Were they late model type center-riser manifolds?....Fred

ursus

Yes plug the riser with a 3/4"npt brass plug and just use the bottom manifold fitting to feed the hose to.

Basically it is the thermostat system that is different not the manifold/riser. They are designed to accomodate either type of thermostat block.

in the 4 outlet thermostat when the stat is closed the excess water exits out the 2 top outlets and this goes to the risers keeping the exhaust flappers etc cool. when the stat opens the heated water from the block exits via the 2 lower oulets this goes to the bottom of the manifolds.

in the 2 outlet thermostat block the thermostat is bypassed by a small channel so some water always flows through and in either case it then goes to the bottom of the manifold, the dif gasket allows for the additional flow sinca all the water now flows through the riser/manifold junction.

fred

Thats just sounds too simple!!....I am going for it....Thanks....Fred