Carb 502 mercruser low compression
 

Hi I have a 1986 welcraft novaiii with a 1994 502 last time out I was at wot and noticed I was loosing rpm when I came off plane I noticed the boat had a slight shake to it and didn't have the power to get back up on plane idled back to the trailer and did a compression test the next day low compression on front cyl on the left side and front two on the right between 60 and 90 psi on them noticed some rust/ coolant on a few plugs (has full closed loop cooling system) and was slightly low on coolant at the time but when I finally looked at the temp when I was back at idle it was not hot but for some reason the oil pressure was like 45 at idle normally its 25 I know I know need to do a leak down test and will in a week or so when I get home from work and up date, my biggest question right now is what could cause the high oil pressure reading and what are the chances of loosing compression on both sides of the engine at the same time or is it likely that the side with one low has been low for a while and didn't notice till I lost the 2 on the other side?

possibly head gaskets if it got hot, check the dip stick for water / coolant

Not to derail the thread but my first boat was a Nova 23xl with a single small block. I beat that thing like a redheaded stepchild. Loved it.

this what im hoping but think I would be awfully lucky if both fails at the same time I pulled the plugs out of my risers and they were pretty pluged up I would imagine that would cause high exhaust Temps. But what I find most strange is the 45psi of oil pressure on a hot engine at idle right after this happened

If water mixes with the oil it will be very thick

or really interesting if any thing figured it would be thiner

Yea, "water and oil don"t mix" but if it is forded through the oil pump and rest of the system it will turn into a thick gue.

So finally got a little further in to the engine and turns out it's actually a mark iv 454 upon removing the valve cover I first noticed one rocker popped off on cyl 1, than performed leak down test and lots of leakage throug most exhaust valves and some intake strangely enough cyl 1 with poped rocker performed best in the leak down test and cyl 5 was leaking to the middle coolant port on the head so the head is prob ruined so any way gonna get the heads looked at. So when I pulled the heads all cyl looked good except one that has a score in it perfectly straight up and down not very deep just bearly ably to catch It with my finger nail

So my biggest questions are what could cause the rocker to pop off and could i get away with honing the cyl with the score and re ringing the pistons?
thanks for any help tried to post pics but says I need 10 points what ever that means

10 posts. Once you post more than 10 times you can post pics. So, just post nonsense or whatever to get there :)

You need 10 POSTS to be able to post pics. Post 6 more times and just post 6, 5, 4..etc in each post