Weird Over heating, need help

[sxpilot]

I re rigged my 21' Daytona with merc 280

Here is what I have and whats going on.

01 Merc 280 powerhead worked my JSRE, bought here on S&F out of LA. consumer Box.
04 15" Mid bought here
and late model Sporty also bought here that was junk and needed rebuilt.

Assembled it with new base gasket, Installed new water pump complete, setback is 16", lower is 1" below pad, fuel pressure reads 30psi all the time, water pressure is maybe 2psi cruzing and at WOT its 8 to 10psi.

Now temps after starting will go to 140 to 150 and stabilize, when I cruze at 40 mph the temp will climb to 180 and throw a code, it takes maybe 4 mins to get there. As soon as I get out of it and come back to idle the temps drop back to 140 150.

Now when I go WOT I get 8 to 10 psi the temp will stay right at 165 to 170 and be stable, I get top speed 94 mph GPS aired out with a Merc Lightning Et 28/29 and 6800 to 7k rpm.

I have checked all the lines, the water passages all look clean, the lower side plates are clean and sealed, the washers in the heads are small hole maybe 3/16 hole.

The pee hole coming from the heads is coming out even for the most part, at speed its hard to tell, but water is coming out, on the lower block hose is also streaming out water.

I thought the lower pick up was getting airated but since I lowered it down its getting clean water.

Any advise guys?

Im getting bummed out at this time, thinking I should have went with a New 300xs...

[Fish]

did you put the keyway back in when installing the new water pump impeller?

[sxpilot]

did you put the keyway back in when installing the new water pump impeller?


Yes,

At first I just replaced the impeller, but after 2 times out with the same results, I bought a whole new assembaly, factory merc parts $$$

[CharlieB53]

If I read correctly, you're getting about 2 lbs cruising?

Not enough flow, try increasing the washer hole size for a little more flow, hopefully that will increase cruising cooling enough and without too much cooling WOT.

[sxpilot]

I tried a larger holed washer with no luck, installed the original ones back in.

Question how many LWPU holes should be on a SM gear case, mine has 3.

[CharlieB53]

Could the by-pass spring be weak and opening too early?

[Dukestor]

Check the end of this thread about decreasing the size of the bypass tubing. It gave me a couple additional PSI across the RPM range. I can still restrict it more if I need more pressure.

http://forums.screamandfly.com/forums/showthread.php?t=151960&page=2

-Duke

[j_martin]

Duke,
I would hazard a guess that there just isn't enough water getting delivered to the powerhead. I'd look for restricted intake, air leak into intake before pump, leaking riser tube, riser tube gaskets (both ends), excessive goo gob in lower reassembly, etc. My reasoning is that if you are getting any water at all out of the telltale, and the pressure is low, it would be cold from too much water flow. Low pressure AND hot at the same time would mean just not enough water coming in.

hope it helps
John

[Jay Smith]

My guess you have pump and or water delivery issues. The larger the holes are on the head washers or any place where spent water LEAVES the block the LESS pressure you will see on a gauge. Pressure readings are created by a restriction if there is NO restriction there will be no gauge indication or an issue with the water pump health of its ability to get water to the engine. . Also IMO 2 lbs crusing is too low and the 8 -10 at WOT is also WAY too low. Most of the 280s I build have 20-25 lbs at WOT. You might have a split or a pucker at thee grommet at the water pump OR the tuner adapter plate where the copper tube enters..Might try looking at that, I have also seen that when a motor is low in the water ( low speeds ) and the water pump is under water and when the rig picks up speed enough to get the water pump areas out of the water and then the motor looses water its most likley that the water pump is somewhere sucking air as it becomes high enought it can suck air instead of being buried in the water where air isn't possible to draft..

Jay Give me a call 1 281 576 5088 cst

[Greg Moss]

The problem is the sporty lower unit. Pull the lower unit and remove the pump base look at the gasket and see the hole from where to suck air. Water is harder to suck that air so as soon as the water pump base is above the water level you are sucking air. Here are some pictures to show you what I mean. It's a bad design. I fill the base area with an epoxy or something you could fill the void with 5200 or something like that to test if that is your problem. With the motor running on a hose see if you are sucking all the water the hose will put out. YOU SHOULD BE. When you pull it apart look at it you will see what I mean. If you have any more questions I'll try to post some more pictures to show you better. I have one here that I can use to take the pictures of.

[Jay Smith]

SXPILOT,
I have a friend in Az. that had a belly full of the Sportsmaster water pump gasket failing issues and had some custom ones made with metal reinforcement like the High Per Base gaskets and his issues are history..

Enjoyed our talk today , call anytime..

Jay

[sxpilot]

Jay I'll get it figured out one way or another, thanks for the knowledge, I'll do what you said first...

Pics of this old heavy thing..

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[sxpilot]

more pics

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[sxpilot]

last ones...

[sxpilot]

280

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