898 log manifold conversion

I want to convert an 898 to center rise aqua power manifolds.
I have tried to use the existing tstat housing with 3 outlets per side and plumbed the new manifolds to flow kind of like the log ones did except from low back to high front with solid riser gaskets and the riser being fed by the top most outlet.
I used the Clymer diagram...
Engine runs fine and keeps around 170 even at wot but the manifolds are so hot I can smell the paint cooking.
Scalding hot to the touch.
Obviously something is wrong.
I have included the diagram I used and a pic of how I have mine plumbed and also a pic of a stock 898 which shows a different arrangement than the manual I think...

Is the picture the right way or is the manual correct?

I have searched other threads and have seen someone use a tstat housing from a Volvo and just run 1 line to the front of the manifolds with pass thru riser gaskets.
Just wondering if the is how Volvo does it as it appears they use this arrangement and the same housing on virtually all their setups.

Is this is any better than the way Merc has tried to do it with so may various tstat housings?

I would rather not have to go through the expense of buying a new housing and replumbing everything if I can avoid it.

Re: 898 log manifold conversion

The best way to do it is to use full pass gaskets between manifold and elbow and have all the water running into the bottom of the manifold. This will also reduce your hose count. I have a drawing somewhere on the different options and how to plumb them up... Give me a few minutes and I'll find it....

Chris.........
EDIT: Here's a thread that was doing the same as you... Have a read and see what you think...

http://forums.iboats.com/mercruiser...center-riser-question-602778.html#post4204080

Re: 898 log manifold conversion

Thank you Chris.
I have mine plumbed the same way as the last "228 warm" diagram but I never drilled bleed holes in the gaskets as the outlet back to the tstat housing is the highest spot....

So then this 898 must be plumbed wrong?

Re: 898 log manifold conversion

Yep, looks that way.

Re: 898 log manifold conversion

So using the warm setup, what should my manifold and riser temps be at idle, cruise and wot?

And conversely, how about the cold setup temps?

Re: 898 log manifold conversion

In post 3 you have the top hose going to the front of the manifold, it should be going to the riser.these are from the merc manuals for log and centerr rise

Re: 898 log manifold conversion

Yes thank you.
That pic in post 3 is not my 898,just 1 I found online that was making me think my setup as per the manual was wrong.
I have pulled off the risers and drilled holes in the gaskets and all seems well on the ear muffs now...
Risers are cool while the manifold is very warm but not scalding at idle at least.

Re: 898 log manifold conversion

Well all is not well after all.
At cruise, the manifolds and risers were way to hot to touch so I plumbed my center rise manifold and risers for the 228 cold setup in the link and now they get so hot at cruise I can smell the exhaust bellows starting to melt.
http://forums.iboats.com/mercruiser...center-riser-question-602778.html#post4204080
Obviously there is not enough flow but why?
Is this a bad water pump?
Bad impeller?
I'm pretty sure the manifolds and risers are not clogged.
The engine temp gauge reaches 165 and stays there at cruise.
What do I check and how?
Maybe I need to get a new tstat housing like maybe the Volvo one with just 1 outlet on either side?

Re: 898 log manifold conversion

You have two hoses routed wrong in my opinion.

Swap the riser hose coming from after the thermostat and put it to your front of your manifold. Your risers arnt getting much water till the motors really hot with the current setup. (Like it is in the original setup pic)

Take the front manifold pre-thermo hose coolant line and put it to the riser. You have two pre-thermo water lines. You will have to figure out which one supplies more water, and repipe the setup. That way your risers are getting the water they need.

I think this will resolve your issue.

I just went through this conversion on my boat. I ended up going to a two line setup and capping the third (pre-thermo) less flow water line.