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1990 454 Tests before purchase

C

carcraze

New member
"Hey all

I have been looking at boat purchases over the past little while and have been looking at one close by.

It is a 1990 454 Merc and I went through the service records and found that it had a frost plug popped, not sure if it has been in the water since. The report says replaced and ran engine all seems fine. Most PPl think frost plugs are some sort of freeze damage preventor but being raised by an auto teacher I know they are sand core plugs from the manufacturing of the bock. There is no hour meter as well, if I put in an offer I would like some conditional tests done on the motor.

I was thnking dry compression as I doubt they will want to run it.
A block water passage pressure test, can this be done easily? I know the BBC can crack internally.
A manifold and riser pressure test, can this be done easily?
Transom moisture test.

I have worked on older Mercs never a BBC though.

Any other tests I should be looking at before a purchase to protect myself?

Thanks all
Mat"
 
"I have seen many of "free

"I have seen many of "freeze" plugs pop with no issues to the motor. Only way to tell is to run it either in the water or with muffs and hose and let it warm up COMPLETELY and monitor the oil.

Check the dip stick before and see that the oil level is where it is supose to be. After running check again. If oil is milky or higher the when first checked ( of course wait for engine to cool a bit and oil to settle) then there may be water in it. All v8,v6 motors can/do crack internally!!!

typically the inline motors crack on the outside due to the water jacket is on the outside.

No easy way to check manifold or elbow when mounted on motor. A good run test should show most issues.

Remember that when running on a hose you are forcing water to the motor. When running in the water the impeller pump is doing the work.
So running in the water is the best test!!!!!!

Make a offer contigent on lake test. NOT land test unless you are sure it is OK!

A compression test is always good but I would run it first and let it warm up.

Does it have a Bravo I outdrive? if so that is great!

also there is more to an I/O then just the motor.

check gimbal ring slop, (steering left to right)at the gimbal ring.

Check the ujoint bellows, shift boot bellows, exhaust does not matter.

If boat has been sittting for a while the impellor may or should be replaced also.

check gear oil it should be clean and outdrive should be full up to the vent plug."
 
"It is a Bravo, not sure 1 or

"It is a Bravo, not sure 1 or 2. The impeller, gimbal bearing, bellows were replaced recently. Have not checked ring slop yet though."
 
"OP your right they are castin

"OP your right they are casting plugs and not "freeze plugs"

The Ghost is good do what he posts.

Consider this why did it pop in the first place someone didn't winterize it correctly, what else is cracked.

Let me guess this is a Florida boat.

My predection: One or more cracks between the water jacket and cylinder. Or the head is cracked, intake manifold cracked maybe."
 
"Thanks for the info. I am ver

"Thanks for the info. I am very concerned about inner cracks, as well as exhaust or intake cracks.This is a MI boat you would think it was winterized maybe too late? I know the service report says it was run and all is okay at this time, but that statement makes me wonder. I will see what contigencies they are willing to accept.

If I can get a lake test or worse case muff test how long running before problems show up like water in the cyclinder from manifolds cracked or oil level affected?

Mat"
 
Well If you use a hose with mu

Well If you use a hose with muffs

My advice would be to minimize the amount of water flowing into the motor. Not full water maybe about 1/2 or a bit less.

Enough to have water flowing and keep the impeler wet but not enough to allow the engine to stay too cool from the cold fresh water. I would say it would take ~ 1/2 hour to 1 hour of run time to allow for full warm up and getting all nice and warm.....
Check oil before and again after all has setteled.

My suggestions.
 
"Thanks ghost, what about mani

"Thanks ghost, what about manifolds, I assume as with my boats in the past if an exhaust is cracked it will drop a cylinder?

The intake possibly the same symptom?

Mat"
 
"At the very least a compressi

"At the very least a compression test MUST be performed. WRITE DOWN THE NUMBERS. Then you will have the base numbers written down for reference down the road.

Then a vacuum test, both done on a warm motor.

Then you will have some idea whats going on internally.

Both in my mind before you even take the boat for a ride."
 
"When there is any doubt as to

"When there is any doubt as to the condition of the motor in an older boat, I assume that the engine will have to be replaced and offer a purchase price based on having to re-engine it.

If the seller can't/won't demonstrate that the boat will pass a sea trial, why should you take the financial risk?....JMHO!"
 
"When I want to check the impe

"When I want to check the impeller's condition on dry land I remove the prop and lower the OD into a plastic 1/4 barrell tub and fill it w/a running garden hose. The impeller has to do its job on its own. If the temp holds at idle and a brief run at 1500 RPM, then it's good enough."
 
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