Adapting 260 cowl to 200 2 piece adapter plate questions

[LakeFever]

98 200 efi with a 260 cover. Everything related to the power head and two piece adapter plates are factory 98 pieces. All cooling is routed as per factory spec. The only variable is the cowl base plate. I am having some hi engine temp worries as I have been running heat cycles to break in the motor. On the hose everything seemed fine. It would idle happily with about 5psi water pressure and stayed cool. I put the boat in the water to run some more heat cycles ( wisecos ) and the water pressure is quite high it runs almost 30lbs at 4000 rpm and the engine temps climb up 160 range so I shut it down. It is possible I’m just being paranoid but I don’t want to be rebuilding this thing again so I’m taking baby steps here. My instincts say something isn’t quite right it seems to be getting too hot. Im running an autometer temp gauge into the port side head sender. My water pressure at 4000 rpm gets up to 30psi so I feel there must be something up with my base plate or maybe a blockage somewhere I missed. I did blow compressed air through the block cooling passages and all the head, rear cover ports too. I was pretty careful with cleanliness of all parts during assembly. The water pressure gauge is tapped into the line coming out of the port on top rear of power head that feeds down to the poppet. Thermostats and poppet all brand new. Water pump fresh too.

Wondering if I missed something with the base plate that might be blocking flow somewhere? The tell tale is flowing very well it’s a 5/16” hose without restriction. The adapter plate feed is a bit of a mess it’s slightly kinked trying to route it between the skirt and the adapter plate. I have since removed the skirt and will be replumbing that hose kink free in case this is part of the issue. I also replaced the head gaskets just in case it was compression pushing water psi up but they looked fine

Any thoughts?

[Jim Speros]

I have not made that cowling change. However The Sea ray white cowled engines in the late 80's early nineties used a plate for lift off cowl. Maybe you can buy those gaskets and compare. You may have to drill some holes in the plate. Don't know for sure.

I do believe your instincts are correct 30lbs at 4000 is entirely too much; 30 lbs at wot is too much.

[Jim Speros]

I found I used 27-99776 1 gaskets. Couldn't find sea ray cowl on any parts lists.

[skialot2]

30 PSI is too high. It is double the pressure you should have. 15 PSI is max. The poppet is the pressure relief. One test you can try is pull out the poppet. Put the poppet cover back on and try it again. Be very carefull not to overheat it. If you still have hi pressure, you have a clog somewhere. If you have no pressure, your poppet is sticking.

[25two.stroke]

I found I used 27-99776 1 gaskets. Couldn't find sea ray cowl on any parts lists.

0A9 to 0C1 serial ranges with the Oyster bucket style cowl. Gaskets will work, the difference is you need a promax stainless base plate, not a 260 one. The promax plate has the little triangle area for the poppet to work correctly. If you don't have that then you wont ever flow right.

[LakeFever]

0A9 to 0C1 serial ranges with the Oyster bucket style cowl. Gaskets will work, the difference is you need a promax stainless base plate, not a 260 one. The promax plate has the little triangle area for the poppet to work correctly. If you don't have that then you wont ever flow right.

I guarantee I do not have a triangle cut out in this plate and I’m 99% sure this is my issue. This is the plate I have. I bought it from a member here who posted up a few years back. Seems his website is down but it looks identical to this. So I have to once again pull the power head and cut a triangle in this base plate for it to work.

Any other issues with this base plate and my motor playing nice I need to worry about? Or maybe anyone know where to buy a stainless promax style base plate?

https://www.buckshotracing77.com/pro...owl-base-plate

[Jim Speros]

On that Oyster cowl engine I had to enlarge the hole in the plate where the water tube comes up. It was half obstructed; probably form the factory. Created a lower pressure issue.

Anyway its something to keep an eye out for if you changing plates.

[LakeFever]

Guys I think the plate has a hole there. I circled in red the hole that goes over the triangular hole. The poppet should not be blocked then right?

[Jim Speros]

I can't tell without seeing it in place but, I would think the poppet relief needs a bigger opening then the hole circled.

I think the poppet relief is on opposite side .

[LakeFever]

I don’t know whether that’s the side that faces the block or the adapter plate. I do know the cowl plate will only go on one way. The listing at buckshot says it’s for promax and race motors so I’m thinking that’s what that hole is for. I might try the poppet removal trick and see what transpires I’m not near tools or parts for a while so I have to make do for now now and I can get that apart so long as I salvage the gasket I’ll be able to test it

[LakeFever]

Ok there is definitely a hole in my plate over the poppet dump. I dug through my phone and found a pic. Snagged a random pic online showing my adapter plate type. It may be that the hole for the poppet is not large enough but I’m thinking it’s well worth the try to pull the poppet back out and make sure it’s not jammed up somehow.

[bigboy]

Make it triangular... should be ok after that modification.

[LakeFever]

The dump hose for the exhaust was pinched a bit so I replaced that. In the lead up to thinking it was possibly the base plate I thought maybe head gaskets pushing pressure so I also replaced those. Went from 0.75 to 1.20 on the head gaskets. The lower dump hose was pinched a bit so I peeled the skirt off and ran a new hose there. I’m going to test this as is and see if there is any change. If not I’m finished with shade tree attempts I’ll wait til I get it back to the shop and tear into the whole deal and enlarge the hole and whatnot. Thanks all, keep ya posted to what comes of this

[LakeFever]

Well that didn’t solve a thing. 10psi at 750rpm idling on the trailer in neutral. Dragging this thing back and taking the power head off the mid again and I’ll see what’s what. Thanks again gents, really appreciate the guidance

[Jim Speros]

10lbs at idle is not normal.