Engine Help please 1989 Mercruiser

[howe719]

So it all started out last summer i noticed that my head gasket was leaking water out the side and down the block so while out on a road last summer she finally died. white smoke all through the water. So after that trip i got home and pulled the head off and replaced the gaskets and put everything right back just as i took it off. I didnt get a chance to check the timing but i marked everything and put it all back the same way. No problems. Started it up and it fired right over.

This year about a month ago was the first time putting it in the water after the head change out project. I noticed that once you would put a load on the motor it didnt have as much power as it had before the head repair. it took i really long time to get up on plane. Once on plane the top speed would be 32mph when before was around 42mph. Also the oil pressure would read 80 psi when use to be around 40 to 50psi.
I thought the fuel filter needed changed. i put a new one on and took the boat out yesterday in the chesapeake. I noticed alittle bit more but nothing big. still top speed of 32mph. oil pressure was 80. I was running for about 20 min and she just died. dead in the water. oil pressure went. i tried to start and it sounded really rough. After letting it sit for about an hour i tried it again and she fired over. To get back to the lunch i just went really slow and she did it again after about 20 more min. I could not get it to start and had to be pulled back.

Any ideas on what this could be or what i need to pull apart to fix this?
I was thinking maybe a new impeller kit, and thermostat maybe. Could it be over heating???

thanks guys

 

[Stamey]

Re: Engine Help please 1989 Mercruiser

You didn't specify the temperature of the engine in your post, so I'm guessing that you don't have a functioning temp gauge. I'd suggest that be the first thing you fix, so as to aid in troubleshooting the problem.

Chris

 

[Failproof]

Re: Engine Help please 1989 Mercruiser

From your description of events, i would not waste much time or money in figuring out your current issues. Start with pulling the oil filter, and cutting it open. Now investigate the metal you find in it. aluminium flakes or bearing material pretty much tells you shes failing fast. If all good with oil, i would look at valve train/lifters as cause of low power. Overheating, the impeller and thermostat.

 

[Eric 3.7LX Alpha 1]

Re: Engine Help please 1989 Mercruiser

Did you torque the heads down correctly in the correct pattern?

Did you set the valve lash properly?

Did you use a repair manual as a guide for the work?

 

[howe719]

Re: Engine Help please 1989 Mercruiser

she runs around 190

 

[oldjeep]

Re: Engine Help please 1989 Mercruiser

If the oil pressure is 80 when it used to be 40-50 then I'd first be replacing the oil filter and if that doesn't drop the pressure into the normal range then either the sender is bad or the pressure relief valve in the pump is sticking.

 

[Bondo]

Re: Engine Help please 1989 Mercruiser

So it all started out last summer i noticed that my head gasket was leaking water out the side and down the block so while out on a road last summer she finally died. white smoke all through the water. So after that trip i got home and pulled the head off and replaced the gaskets and put everything right back just as i took it off. I didnt get a chance to check the timing but i marked everything and put it all back the same way. No problems. Started it up and it fired right over.

This year about a month ago was the first time putting it in the water after the head change out project. I noticed that once you would put a load on the motor it didnt have as much power as it had before the head repair. it took i really long time to get up on plane. Once on plane the top speed would be 32mph when before was around 42mph. Also the oil pressure would read 80 psi when use to be around 40 to 50psi.
I thought the fuel filter needed changed. i put a new one on and took the boat out yesterday in the chesapeake. I noticed alittle bit more but nothing big. still top speed of 32mph. oil pressure was 80. I was running for about 20 min and she just died. dead in the water. oil pressure went. i tried to start and it sounded really rough. After letting it sit for about an hour i tried it again and she fired over. To get back to the lunch i just went really slow and she did it again after about 20 more min. I could not get it to start and had to be pulled back.

Any ideas on what this could be or what i need to pull apart to fix this?
I was thinking maybe a new impeller kit, and thermostat maybe. Could it be over heating???

thanks guys

Ayuh,.... Go back, 'n Finish what ya started....

ya had the motor apart, 'n never set the timing....

 

[tpenfield]

Re: Engine Help please 1989 Mercruiser

My 1991 Mercruiser 7.4L recently got trashed after a top-end rebuild. It turned out to be that there were leaks around the valve stems. It was not apparent during the rebuild as it looked like an exhaust manifold issue. So, your issue could be more than the head gasket.

190 degrees seems a bit hot for that engine.

I would get the timing set and see if it acts the same. If so . . .

I would do a compression test and a cylinder leak test.

I would also do a pressure test on the cooling system to see if you are leaking water somewhere and it is going through the engine (I hate it when that happens )

since you are in PA, I assume this is fresh water ??? a 20-something year old engine could have some issues though . . .

 

[howe719]

Re: Engine Help please 1989 Mercruiser

Alright so here is what i found so far. The motor is turning over just fine when cold and will run. So i pulled lower unit. Impeller was kinda ok. some of the fins were cracked. So i am putting a new one on. New stat. Changed the oil and filter.

After i changed the oil and filter i started it up and checked the timing. The timing was running about 8 BTDC. I adjusted to 12BTDC and set the idel down alittle. The oil pressure is around 78 now. Why still so high???????

I will have to put in the water in a week or so and try and run it.


Any other thoughts i could check while she is out of the water???
thanks
alex

 

[LAC_STS]

Re: Engine Help please 1989 Mercruiser

My 5.7 which is an OMC but I would think it would be the same is supposed to be set at 8 BTDC when using 89
and higher octane fuel and 2 BTDC when using below 89 octane fuel.

Are you using the same weight oil as before? If I use 30 weight oil my oil pressure usually sits around 45-50. but if I use 40 weight oil it is around 70-80.

 

[howe719]

Re: Engine Help please 1989 Mercruiser

After installing all new items, stat, impeller, oil change, timing adjusted.

Hooked the water up and fired it up. Running great!!!

Problem. after running around 15 mins or so i shut it down and i noticed water that was on the motor was boiling around cylinders 3 and 4. These are the middle cylinders on the motor across from the carb. I also noticed that the temp only said around 165. This is good to me. I could heard the motor boiling inside which was what i heard when i broke down in the first place.
Whatever is causing that area to get hot is causing my issue. I also notice that the paint around that area of 3 and 4 cylinder was burnt off. No where else on the motor is like that.
What would be causing those areas to get hot like that????

I am using a 195 stat but i have always used that type and never had problems

thoughts????

 

[ktbarrentine]

Re: Engine Help please 1989 Mercruiser

A 195 t-stat? is that what the manual calls out? Sure seems high. My manual says 143 degree t-stat

 

[Stamey]

Re: Engine Help please 1989 Mercruiser

The reason the water boils in the middle, and the paint is burnt off, is because that's the exhaust crossover to warm the carb. That's normal.

Chris

 

[howe719]

Re: Engine Help please 1989 Mercruiser

Took the boat out this weekend and she ran great! Motor is back to the way it should. Only other issue i had this time out was the outdrive went. not sure what happen but was hearing this loud winey noise and then she stopped moving. I will have to pull apart to find my findings.

thanks guys

 

[ktbarrentine]

Re: Engine Help please 1989 Mercruiser

Still wondering about the 195 degree t-stat, but willing to let that one go by... Will standby to hear what happened to your drive. Recommend you start a new thread for that. KTB

 

[howe719]

Re: Engine Help please 1989 Mercruiser

I started a new thread but i knew what happen already. Bearing went on the vertical drive in the the upper unit which let play between gear heads. It tore the all up. had to but a upper drive rebuild kit, $400. I am having a problem trying to pull the bearing race from the upper drive. its a bit**.

The 195 t-stat, i ended up switch to a 165- on last run. seemed to keep the temp down and run much better

 

[Don S]

Re: Engine Help please 1989 Mercruiser

You shouldn't have more than a 160? thermostat in that engine. NEVER a 195. You don't have a car, you have a boat.

 

[ktbarrentine]

Re: Engine Help please 1989 Mercruiser

I thought his manual called for a 143 t-stat... At least that's what I saw.