Hello - first, I have to say this is my first post but I have found many useful threads in the past so thanks everyone for all the help. Second, I do have some experience working on boats and PWC but certainly not an expert. I have done bellows jobs, rebuilt trim units, installed water pumps, etc. Third, I did look for a similar problem but could not find one so here goes.
1991 Mercruiser 7.4L I/O with bravo out drive
I purchased the boat in April 2013. Appeared well taken care of and stored in heated storage. Brought it home and had starting issues. After throwing in a re-manufactured starter and new battery......we were on the water and running smooth. Two weeks ago, we were out all day with no issues. Brought the boat home and parked it in yard with cushions up and all opened up to air dry before covering. over the following 2 weeks, it rained hard several times just in time to prevent the cover going on. This is a carberated model with the round air cleaner. The threads on the rod that hold the air cleaner and black cover on were messed up so the black cover was off leaving the air cleaner on carb held on by zip tie while I ordered a new threaded rod. OK - enough background
Getting ready for the lake a few days ago, I hooked up to muffs as usual and turning over........the starter gear would just grind on flywheel. Few more attempts with same results so I assumed it was the cheap starter I purchased. Replaced starter with same results. Pulled all plugs out to relieve compression and allow me to crank over by hand when.........water was coming out of SOME cylinders as I removed the plugs. A lot of water!! Checked oil and it was way high. Cranked over by hand a few times and shot water out of plug holes then tried key. This time, starter engaged and motor turned over also shooting some residual sprays of water out plug holes. I changed oil & filter and attempted to dry out plugs as well as make sure water was out of cylinders. First I sprayed wd40 in each hole to provide some lube while turning motor over to blow out water. After I felt all water removed, I put plugs back in and.............starter not engaging again. Pulled out 2 plugs one side, 2 plugs other side and same thing. Pulled out 3 of 4 remaining plugs so now with 1 plug in..........starter did engage and turn over motor but then did same thing and started grinding. I pulled out last plug and tried a compression tester but again same thing............started turning over but stopped. OK - so now, I have put some oil in each cylinder, ratated a few times and let sit. Did that 2 days to make sure cylinder walls are lubed up.
My assumptions are:
The hard driving rain got water in motor through air cleaner but there was a lot of water in there. I drained almost 5 gallons of water/oil out and it only holds 8 quarts.
It ran too good to be a head gasket issue and the oil level was not high before sitting.
I also believe it was rain due to only some cylinders having water due to some valves being closed
I do not believe it is a manifold seal issue since I had the muffs hooked up after the oil change for a bit and the oil level did not rise any.
What is puzzling me so much is ......why does any back pressure at all.......even just a single spark plug installed......prevent the starter from engaging the flywheel? I realize I may have damaged the teeth on starter gear with the grinding but........it does engage when no pressure in motor.
Thanks for any suggestions you may have.
1991 Mercruiser 7.4L I/O with bravo out drive
I purchased the boat in April 2013. Appeared well taken care of and stored in heated storage. Brought it home and had starting issues. After throwing in a re-manufactured starter and new battery......we were on the water and running smooth. Two weeks ago, we were out all day with no issues. Brought the boat home and parked it in yard with cushions up and all opened up to air dry before covering. over the following 2 weeks, it rained hard several times just in time to prevent the cover going on. This is a carberated model with the round air cleaner. The threads on the rod that hold the air cleaner and black cover on were messed up so the black cover was off leaving the air cleaner on carb held on by zip tie while I ordered a new threaded rod. OK - enough background
Getting ready for the lake a few days ago, I hooked up to muffs as usual and turning over........the starter gear would just grind on flywheel. Few more attempts with same results so I assumed it was the cheap starter I purchased. Replaced starter with same results. Pulled all plugs out to relieve compression and allow me to crank over by hand when.........water was coming out of SOME cylinders as I removed the plugs. A lot of water!! Checked oil and it was way high. Cranked over by hand a few times and shot water out of plug holes then tried key. This time, starter engaged and motor turned over also shooting some residual sprays of water out plug holes. I changed oil & filter and attempted to dry out plugs as well as make sure water was out of cylinders. First I sprayed wd40 in each hole to provide some lube while turning motor over to blow out water. After I felt all water removed, I put plugs back in and.............starter not engaging again. Pulled out 2 plugs one side, 2 plugs other side and same thing. Pulled out 3 of 4 remaining plugs so now with 1 plug in..........starter did engage and turn over motor but then did same thing and started grinding. I pulled out last plug and tried a compression tester but again same thing............started turning over but stopped. OK - so now, I have put some oil in each cylinder, ratated a few times and let sit. Did that 2 days to make sure cylinder walls are lubed up.
My assumptions are:
The hard driving rain got water in motor through air cleaner but there was a lot of water in there. I drained almost 5 gallons of water/oil out and it only holds 8 quarts.
It ran too good to be a head gasket issue and the oil level was not high before sitting.
I also believe it was rain due to only some cylinders having water due to some valves being closed
I do not believe it is a manifold seal issue since I had the muffs hooked up after the oil change for a bit and the oil level did not rise any.
What is puzzling me so much is ......why does any back pressure at all.......even just a single spark plug installed......prevent the starter from engaging the flywheel? I realize I may have damaged the teeth on starter gear with the grinding but........it does engage when no pressure in motor.
Thanks for any suggestions you may have.
