Adapting 260 cowl to 200 2 piece adapter plate questions

[NZ Sidewinder]

30psi at 4000 with 2 piece plate suggests to me that all the cooling water is trying to squeeze out the tuner spray holes, the spray hole poppet dump and that small 3/8 poppet hole which should be a triangle.
That 3/8 poppet hole is too small.
Top hose

[LakeFever]

30psi at 4000 with 2 piece plate suggests to me that all the cooling water is trying to squeeze out the tuner spray holes, the spray hole poppet dump and that small 3/8 poppet hole which should be a triangle.
That 3/8 poppet hole is too small.
Top hose

it sure seems you are 100% correct. There was two issues the tuner spray hose was not plumbed very well and that hose was kinked. I have since corrected this with the two 45 degree fittings above. Then the 3/8 hole which I opened up to a triangle. The pressure drop from those two adjustments was dramatic so we definitely found the trouble. The pressure now seems to low so I’m hoping restricting the tell tale down to oem size will bring everything back in line to at least 10+ psi of water pressure. I’m also going to replace that plastic washer it has a warp to it so that can’t be good. Even though the poppet carrier is in tight I’ll stake it some more and triple check it’s all in good order. I don’t think the water pump is suspect because I went from 30psi to 8 just by doing these mods with the same water pump. I’m also replacing the lower unit shortly anyways with a brand new unit so a new wp will be going on.

Based on the huge pressure drop I managed by opening up flow it seems sensible to think restricting it at the tell tale should bump it back up. Adding the aluminum washer makes sense for a couple reasons firstly because it seems suspect from other member’s experience and the fact that I was over pressuring the system may have hurt it. Aside from those two details I can’t think of anything else that I should address. Again I appreciate all the input

[LakeFever]

I think I found the problem. The gaskets. I purchased a pile of gasket sets from the beginning along with a new poppet valve kit all from promarine. Well, as it turns out the gaskets in the promarine kit are 0.0056” thick, which is what was on the motor during my crazy high water pressure experience. When I opened up the hole to the triangle I opened up the poppet again to make sure all was well which it was by my eye. I reassembled it and that along with the triangular hole made a massive drop in water pressure. Today as it about to button up the new aluminum washer in my poppet I happened to notice the first gaskets I installed looked different so I measured them with calipers and they are exactly twice as thick as the poppet gaskets that came in the master gasket kits I bought two of way back. These are 0.0028” thick and that is the gaskets I was running last time with low water pressure and presumably normal coolant flow because it was running fine.

I did a quick search on the thick gaskets and see that this is a fairly common complaint so I believe the entire high water pressure problem was the thick poppet gaskets. Thankfully I have a third set of thin ones and I’m assembling now with the aluminum washer and tell tale orfice reducer and I’m thinking this is going to be resolved. Crazy

gasket with no writing on it is the thick one.



this is the kit and manufacturer with the thick gaskets

[NZ Sidewinder]

I use the thick cork gaskets.
This current build I'm going to try build a tell tale that is small so it doesn't dump to much flow, but still won't block up and cause unnecessary concern for the race driver or pit crew.

[LakeFever]

Well I surely thought I was onto something there. Just seems a bit nuts that opening a hole up can make such a big pressure drop. Figured it had something to do with the diaphragm not being squeezed properly or something along those lines. Ah well it’s all buttoned up now only thing left to do is try it and see how she goes

[LakeFever]

Well seems we got this sorted thanks again everyone. The little mods made some gains, nothing crazy but it holds steady 10psi now at 4000rpm. It may hold more but I was jacking my motor up until I saw the pressure start to vary up/down and I jacked down just a little from there and ran it. Almost every time I glanced at it I saw 10psi so that’s enough right? Might be more at higher rpm I wasn’t looking at it I was too busy having a blast.

Temp gauge sits steady right at 180 indicating which is 140ish actual. I don’t mind that the gauge is reading high because 180 is perfectly straight up pointer which makes it super easy to keep an eye on. Going to leave that as is. At this point my focus is going to go towards my new lower unit. Then I’ll be feeling more confident about airing this thing out

[NZ Sidewinder]

Where is your temp sender?
On my poppet system 225 promax I put a sender in the too of each head, very close to the stats.
At idle I'd see 70/80deg C, ( 140f)
But underway, it would drop off to 40deg C (70-80f)
At first I'd stop each time it got to 40C and let it warm up at idle again.
I was very concerned.
Then I gave up on it and just drove it.
Went real well.

[LakeFever]

Factory port side head temp sender. No clue what the ohm sweep is on the sender or the gauge. Don’t really care at this point now that I’m feeling it’s not going to burn up and I have 180 to read knowing it’s much lower actual I’m good. Funny thing about gauges sometimes ignorance is bliss

[NZ Sidewinder]

Someone who knows just recently said to me, the worst thing you can do is put a temp gauge on a v6 merc.
Toyota have this same policy with their 1kz-te diesel engine.
The gauge is dumbed down so there are just two readings.
Normal and fried.