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Need advice. Exhaust manifolts and risers

S

staffan80

New member
Hi,

I am new to the boating world and i am going to try to make my story as short as possible :)

This summer i bought a Maxum 1900sr 2001 model with a mercruiser 4.3l gen + engine. I did not know anything about boats before this and not that much of engine in general. The boat looked great and only litte over 90 ours on the engine. The seller had change oil and filter before storing it for the winter. He did not pour antifreeze in the water system but drained the engine.

Fisrt day the enginge run good but when i took it out the second day it started to hesitate and misfire. After this my father in law took it out for a spin and it died completely. I managed to get the engine going again by replacing the coil, ignition sensor in the distributor, sparc plugs and fuel filter. But the engine would still misfire after it was getting up to working temperature.

I have spent many ours reading forums and the service manual and decided to do a compression test. It showed that there was zero compression on the left middle cylinder (other cylinders were in spec)
I have now taking of the cylinder head and it showed there was a leaking exhaust valve. The head is now sent to a machineshop to get it fixed but i wonder what can be the cause of all this?

There is rust in the manifold from water so i guess water has broken the valve. Inspecting the manifold, riser and spacer seems to be in pretty good shape, dont they?
I have pressure tested the manifold by poring acetone in them and check for leakage. Not a drop passed in to the exhaust ports. One thin i noticed when i worked with the engine is that one of the exhaust flapper wings has broken off and the tubes going from the carburator to the valve cover was not properly installed. The pushrods is also fairly rusty at the top near the rocker arms

I took some pictures of the manifolds. Should you replace this? they are fairly expensive here in Sweden :(

Excuse poor English
Kind regards Staffan

DSC_0292_1.jpgDSC_0294_1.jpgDSC_0295_1.jpg
 
Jag ska prova det här sättet, och även i den engelska versionen http://www.bing.com/translator
En ventil fastnat/skadad pipa är oftast min vatten in i cylindern. För att testa grenrör, stödja dem upprätt och med hjälp av en slang som kommer att gå ovan th vridbart ther grenrör, fylla den med vatten upp till toppen av grenröret och låt det sitta en dag eller två.Watyer kommer ut på pipa hamnar signalerar ett fel.
Pipa grenröret kan testas på samma sätt med ett modification.you behov att försegla den inre hamnen med en plugg av något slag att hålla insidan torr.Försegla vatten hamnen att hålla vattnet.Stöd ståndaren med facken inför uppåt, med slangen igen, fyll med vatten till toppen av riser och Låt sitta. Om vattennivån går klänning och det är vätan inne i hamnen, ståndaren är läcker och som var orsaken till vatten intag.
Ed

I`ll try it this way, and also in the english version http://www.bing.com/translator
A stuck/damaged exaust valve is usually my water entering the cylinder. To test the manifolds , support them upright and using a hose that will go above th etop of ther manifold, fill it with water up to the top of the manifold and let it sit a day or two.Watyer coming out the exaust ports signals a failure.
The exaust manifold can be tested the same way with a modification.you need to seal the inner port with a plug of some sort to keep the inside dry.The seal the water port to keep the water in.Support the riser with the slots facing upward, using the hose again, fill with water to the top of the riser and let sit. If water level goes gown and there is wetness inside the port ,the riser is leaking and that was the cause of water ingestion.
Ed
 
The pushrods is also fairly rusty at the top near the rocker arms
Click to expand...
Did you remove the other valve cover and inspect the valve train? You may also see a little rust there similar to the other side. Rust can occur from using the boat for short trips whereby the engine oil does not get hot enough to cook off any moisture that occurs naturally during combustion. Check the thermostat to make sure it is working. A 12 yr old boat w/only 90 hrs on the engine does not help it. It means it sat most of the time w/moisture contaminated oil in the block caused by short trips.
 
Thank you for posting back,

I will pressure test everything again from Bt Docturs instructions. If they passes the test, would you guys still replace them or would you be confident putting them back in the boat?

guyjg: Yes, i have removed the other valve cover and it is the same story there. The top of the pushrods are rusty and the oil contains water (Milky wihte/yellow). The dipstick oil is perfectly fine. I am pretty sure the boat has always been run short distances, Because it has been stationed in a very small freshwater lake.

I am thinking about order everything from the US, Do you recommend a supplier that have good prices and will ship to Sweden?

The parts that i am sure off is:
Thermostat with gaskets
New intake gaskets
New head gaskets
New carberator gasket
All new pushrods
New shutters/flappers

Parts not so sure about:
New mainfolds, spacer and elbows
New Head bolts (They look fine but must they be replaced?)
New intake bolts (They look fine but must they be replaced?)

Thanks in advance :=)
 
Ayuh,.... I'm gonna Guess that yer water was comin' from 1 of the gasket joints, either coulda been leakin',...

Havin' manifold, 'n riser blocks, then elbows is twice as many gaskets to leak,...
It almost looks like water tracks on the riser block in the picture passin' into the exhaust,..??...

Inside the manifold, I see abit of rust, how far up inside can it be seen,..??
Rust tracks generally point ya to the leak,....

I'd clean up the gasket surfaces by millin' 'em Flat, or atleast dressin' 'em Flat, with a flat file,...
Then throw on a set of Mercruiser's carbon metallic type gaskets, 'n run 'em,...

I Hate those green paper gaskets myself,...

Donno who ships parts where, but the head bolts, 'n intake bolts are plain ole reusable bolts,..
 
This company ships WW. http://bpi.ebasicpower.com/index.php The exhaust mans., risers and elbows can be ultrasonically cleaned by a radiator shop. They should still be good since they were used in fresh water. You can buy refurbished pushrods if they are available to save a little money.
 
i finally got sick and tired of those cast 2 piece heavy weight manifolds,and got on to some 1 piece stainless ones,less than 1/4 of the weight of cast iron ones,beautiful extractor design of the exhaust flow,absolutley no chance of coolant leakage,sounds better and goes better,only down side is the cost,HY-TECH is the brand name,come from australia,there is some retailers in USA,can highly recommend.
 
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