help with overheating issue...this is long
 

this is my old boat, I am trying to sell, hence want to diagnose and repair myself rather than take to a marina.
not the Formula which runs perfect

1991 454 carb engine, closed cooling, antifreeze in block and exhaust manifolds. open exhaust with inline mufflex mufflers, bravo 1
24 ft bowrider.

i need to determine if i have an internal engine issue or a cooling system issue or other stuff i haven't thought of
this is long but i want to provide as much info as possible

the engine is a complete used drop in I installed about 4 years ago. It has always run hotter that i thought it should,
about 190-200 under load and wot. installed on existing transom and outdrive,
old engine didn't run hot. cratered from rotten manifolds
and crankcase full of water.

last year I installed new seawater pump, took heat exchanger and oil cooler end plates off and checked coolers which seemed ok.
didn't remove oil cooler just checked for water obstruction.
main heat exhanger tubes clean as new.
took thermstat out to see if that would help but it didn't.

first trip out this year, it ran ok but still hot, over 200 deg after about 10 minute wot run.
shut the engine down shortly after that and restarted after about 5 minutes and it billowed oil smoke, lots of smoke, out right side exhaust only.
since it was oil smoke and one one side, I assumed valve seal. changed the seals and found no fault with old ones.
took the head and manifold to engine shop for pressure testing and had the head vacuum tested too.
had manifold gasket surface surface planed.
all checked out ok.
put back together with new gaskets, plugs etc and then test run,
still overheats. but no more smoke
checked timing and found was 12 deg at 1000 rpm. set to 8 degrees

another test run and still hot,
this time it pucked a bunch of oil into bigle, 2-3 liters
on this run when it got hot, it felt like it was tightening up, actually losing rpm until backing down on the throttle.
it idles fine, cruises on plane fine, just doesn't like high rpm.
has lots of oil pressure, 30-60 psi depending on rpm
i think the oil came out the dip stick tube or fuel pump gasket
didn't come out of valve cover, head gasket, front seal or oil pan gasket
right front lower corner of engine was soaked in oil.

cleaned it all up at home and ran on hose looking for oil leak, runs perfect, no leaks, seeps, drips. stains anywhere.

then did a coolant system pressure test and holds 17 psi for 5 minutes, that should be good.
bought a combustion gas test kit for the coolant and ran it
twice as long as recommended and perfect, no discoloration whatsoever in test fluid.
engine oil is clean and no indication of coolant in oil.
checked timing again and it is ok.


so, next step...
1. to determine if i have an internal issue is a compression and/or leak down test.
i can do a compression test at home but don't have a compressor to do a leak down test.
if it passes compression test, can i forego the leak down test?

if it passes compression/leakdown, it should be safe to say i have a cooling issue????

2. the other thing IS.. the marina i bought the engine from told me to run straight dexcool which i thought was odd, but fiqured he knew.
i have done some checking and straight dexcool can cause a temperature increase but should not lead to the level of overheating i have.
when it stops raining i will drain and backflow the coolant system and mix to 50/50 water and dexcool ,
don't want to change to green a/f, if i don't get all the d/cool out, they don't mix well.
i will reinstall thermostat as well

3. is it possible to time it on the 8 deg mark if i have the distributor out a tooth or out 180.
i checked the dist cap and plug wire #1 is on #1 on the cap and #1 on cap is front and center where it should be.
i was told timing should be checked at 1000rpm but operators manual says 8 deg at idle, which is coreect

4. it appears my coolers are ok, seawater pump and
circulating pump appear to be working,
there appears to be lots of water out the exhaust,
risers and end caps on coolers are cold to the touch under normal running, haven't checked at high rpm/load

how can i check that i am getting enough seawater flow from outdrive to s/water pump.
this is ocean water, eastern canada, the water still cold

in summary, works great till high rpm/load, but cooling issues could be related to boat speed as well, not getting enough water in pick up to s/water pump.

what have i missed??

you are probably correct on the engine life expectancy but i still need to determine source of problem.
if i pull and rebuild or replace the engine and still have a water pickup issue, i am back to square one.
if have re-read my post several times and it seems more like a boat speed issue rather than engine speed,
but i don't know how to check/test the water pickup volume

To check the water pick-up, I would think a water p.s.i. gauge could be installed faily cheap. Have you checked fuel pressure during your WOT runs? If it is running out of fuel or losing fuel pressure at the time when it needs the most fuel, the engine will run hotter, again a fairly easy check wheather it is a temporary gauge or permanant. On the timing thing, First since you are having problems, remove the #1 spark plug and position the #1 piston at EXCACTLY TDC by feelling with a screwdriver in the hole while rotating engine by HAND, and check to see that your timing mark is alighned with your timing pointer. I've seen them slip on the balancers and will through the timing way off. And if you could get a timing light with the adjustment dial on it to check your timing at high rpm to check 'total timing' This usally done around 3500 rpm or so. Not sure excactly, but it should be around 32-36 degrees total timing.

thanx for the tip on the timing, i can do that.
fuel pressure gauge shouldn't be too hard to rig, what should f/pressure be?
i will look at the raw water plumbing and see where i can put a gauge. what number should i be looking for

If the water intake is in the drive, check the hose and fittings between drive and transom housing. if they are old and cracked they suck air once the boat is on plane and they are out of water. At low speed they are under water so the dont suck air (idles speed). If it comes thru bottom take hose off and check thru hull fitting for blockage.

i think it extremely unlikely that it is a tuning issue of any sort. you are running about 250 galls /minute of not thermostat controlled cold water thru that system... if the motor were lean enough or advanced too so much as to cause that volume of water flow to heat then the combustion chambers would have to be as hot as the surface of the sun and you would certainly experience other far more obvious symptoms...

i think whoever mentioned the water pickup is probably correct in one fashion or another. what i have seen with my own eyes was this exact problem being caused by the hose from the water pick up to the pump being both old and not wire reinforced and getting sucked closed by the pump...

that boat did exactly the same thing .

you didn't do something foolish like when you had the motor out, jam a rag in that hose and forgot that its there, did you ?

good points about the tuning, i am going to check compression for peace of mind.

the hose from the transom to the s/water pump is reinforced with a coil.
the water pick up is in the drive above the tube for output shaft, normal bravo 1 setup.
again, there is lots of water coming out the exhaust but maybe not enough
i will pull on water pump end of the hose off and and check for flow on the hose in the driveway,
if ok , i'll pull the drive if i have to and check transom for hoses leaks or blockage.
i'll also try and find a place to put a gauge on the raw water plumbing, there may be a bung in the heat exchanger housing.

sorry. missed the part about plenty of water coming out the exhaust...

this isn't something dumb like a bad sending unit for the gage is it ? i mean... is it really at 200 ?

it does run hot, pucked oil out the dipstick, engine tightens up when hot, have seen as high as 220 on guage,
exhaust is steam when hot.
actually i don't know where the oil come out. i know it didn't come out the valve cover, head gasket, front seal, pan gasket.
that leaves dipstick or fuel pump gasket, neither of which leaked after clean up and restart in driveway.
gotta determine if it's sea water problem or engine circulation
problem.
next sea trial i have an infrared temp sensor i can check variuos temp points with as well