what all could cause water in my oil of a 99 4.3 mercruiser?

i took my boat out at begining of year and was out for about an hour..it idled and ran great not under pressure but when it was in gear moving it seemed straining and wouldn’t go over like 25 and it was a lil shakey…well i winterized it last year by running fresh waer through it then i drained the block put the plugs back in then hooked a container with 5 gallons antifreeze to the muffs started it and ran all the anitfreeze in shut it down and left it alone all winter…in spring i changed the oil…..after i ran it for the first hour i checked the oil and it seemed a lil high, at first i thought it was getting gas in the oil but i checked it out by pumping some oil out and come to find out it looked like milk so it’s water in there…is there any other possibilities besides a cracked block i should check b4 replacing? thanks for your time
already checked compression on all cylinders and they are fine all firing at 165psi….would the head gasket go bad just from sitting through the winter? it was fine all last year…i was told by my father when it got in the negatives he seen antifreeze had oozed out the lower unit where u hook the muffs to which makes me think something froze but i don’t understand how anitfreeze would freeze makes no sense to me

Antifreeze in my Inboard Mercruiser… Two questions…?

I have successfully winterized my Mercruiser 5.7L Inboard Ski engine and follwed the service manual for each step – fuel stblz; fogged; water block drain; ect…

I have two questions:

1. Online, I have read alot about filling the open-cooling water system with antifreeze to avoid block cracks. The service manual has no instruction for this step. Has/does anyone do/have experience with this?

2. When I drained the engines lowest water block valves, I notices a bit of rust on the tip of the plug, the first bit of water appeared rusty when drained…should I be concerned? Is this a sign for problems, or is dirty water and a bit of rust normal for an open water cooling Mercruiser engine?

2005 mercruiser 4.3 L I/O won’t run above idle?

It has a little trouble starting, and the engine doesn’t sound quite right when its just idling. As soon as any throttle is applied, the boat dies. The interesting thing is after the boat had been sitting all winter, it started right up and I could accelerate to cruising speed for about 2 minutes, when it suddenly dropped rpms and died, and hasn’t run above idle since then. It also smokes a little out the back and from the cover with the mercrusier logo when trying to start it after pumping the throttle to give it gas. It is NOT water in the gas, we put seafoam in it and a mechanic has checked it out and replaced the fuel filter, so now I’m thinking its the fuel pump or carburetor. Any ideas? It worries me because it is so new, only 150 hours on the motor, we bought it used last year but the owner was anal about taking care of his boat, it was pristine and ran fine all last summer until the end of the season when we had this same problem.

BOAT ENGINE (MerCruiser GM 305) PROBLEMS!?

Hi, I have a 1983 MerCruiser GM 305 marine engine. The engine wont run right and boat wont even plane out. It was running not great but would plane out and get up to 3100 RPM, then I checked timing with a timing light and it was way off thinking, “oh I fix it it must be the problem” well I made it worse and cant get it back to were it was running at 3100 RPM. So now I got a boat that will get up to 1500 RPM. Here is all I did, I rebuilt Carb, new points, new condenser, new plugs, new wires, new filters(gas,oil,water separator), belts, did compression check(155psi is all) and new distributor cap. On my manifold is says it should run at 4400-4600 RPM and I have only seen it run like that when I first bought it 2 years ago and that only lasted a month or so. I don’t want to have to rebuild engine as I just rebuilt one for my race boat. Also the boat misses. I don’t think it is the cam, or timing chain as it was running OK while running at the top 3100 I got out of it a few days ago. I want it back to the 4500 RPM it is suppose to be. I need this running soon as this is my charter boat.
Thank you
I checked the mechanical advance at the distributor

175 hp mercruiser GM 4.3 L V-6 alpha one loses power?

After WOT or near WOT for a few minutes rpm drop and boat slows. I have checked a plug, it was fine. I sprayed the carb out with carb cleaner and put water remover in fuel tank, same thing still happens.

Mercruiser 470 backfires out of Carb

My 1983 Mercruiser 470 started to break up while on cruising rpm. Now she is not getting full RPM, I’m getting 3500 and then for short spurts, she goes up over 4000, but back to 3500 to 3800 RPMs. On the starts out of the hole, she pops out of the carb and sometimes stalls out. Also, I have found that when I punch it from idle, there is a hesitation before the engine responds with either the lean pop or acceleration. I have changed the point and condenser, changed the fuel filter and even add a Racor 10 micro Fuel Filer / Water Separator…but I still have this issue.

My Mercruiser I/O sputters, sometimes to a stall. It revs fine, but terrible idle. Any solutions out there?

I’ve thought about water in the gasoline, and have put Prestone Water Remover in the gas tank.

I’ve thought about the fuel filter, but from what I’ve read, if the filter was bad, then it would sputter when I accelerated, which it does not.

The boat accelerates just fine, zero issues. It idles extremely rough and stalls when put in gear if you don’t rev the engine right away. It will also stall if left in idle for more than a minute.

After scouring the internet, I’m at a loss. What could be the solution?

Mercruiser Alpha 4.3l V6 losing power and smells like gas?

I have a Mercruiser Alpha one, 4.3L, 175 hp. Runs great when first starting, including 25-30 mph speeds, with OK acceleration. But after running for 5-10 minutes, it severely hesitates under heavy acceleration from a stop, has small backfires, and even quits running altogether during the acceleration. Upon re-starting, it idles fine, and will run fine under 10 mph. But at this point, will not run normally above those speeds and we can smell gas (like its not burning all the fuel). Suspected bad gas (water), so I added gas treatment and topped of with fresh gas, seemed to slightly help, but problem persists. This is the first time we’ve started the engine after the winter season.

5.7L mercruiser engines stall out after running for 20 min?

1989 32′ Carver with the original merc 350ci engines. have had the boat for 4 years. engines start/run/idle smoothly and powerfully. when first started and warmed up, the engines will run 3000 to 3200rpms (about 14/15 gph) for an hour with no problems. one motor will suddenly stumble, like it’s not getting fuel. it will pick up again, and stumble, worse and worse… backing off the throttle all the way and shutting off the engine for 1 minute, then restarting – it will run perfect again for 20 minutes? it happens to both motors randomly – with two completely independent systems. (different fuel tanks/lines/pumps/filters…) have changed the filters (both in-line and fuel water separators) numerous times, and see no visable particles, nor any significant change. pulled the pick up line out of the tank and inspected… nothing notable. ideas?
Thanks for the input! more info -