87 3.0 Mercuiser works great! then..........

[Smacken]

Hi All, I just purchased an ol fixer upper. Its an 87 Starcraft with a 3.0 Mercuiser, 140hp, with an Alpha 1 drive. After sending it for service (this thing was in bad shape and not well looked after) I was pleasently surprised with the results. The boat idles great, started like a charm, 150lbs in all cyliders, oil looks like it was just changed after 8 hrs of running and every guage works!. My problem is lately that after I take it our for an hour or so, (Temp around 130 running) and load it on the trailer, take it home and go to flush the motor, it wont start? I'm on my second starter now, and I'm drawing a blank as to what it might be. The first time this happened I took out and cleaned the plugs and the cylinders appeared a little gassy, put the plugs back in and it ran like a top, and started with a little hesitation but it did go. I took it to the river and it ran great for approx 1.5 hrs, loaded it up and same thing happened when I got home. For the record rpm @ WOT is 4800, and I generally cruise at 3800-4300. Sorry for rambling but any sugestions would be apreciated.

 

[Cuyose]

Re: 87 3.0 Mercuiser works great! then..........

Does it do the same thing on the lake? Do you shut down for an hour or so and try to start it back up and does it run fine then?

I have had weird issues with bad gas in the tank, and when trailering it shakes up some of the gunk and wont run right after a ride on the trailer to the lake, when it seems to run fine on the trailer at home. This is opposite from what you are experiencing though.

Next time after you get home, take the flame arrestor off and check what the carb looks like prior to starting it up. I suppose you could have a stuck choke or excess gas leaking into the carb.

Some other people might be along with some other ideas, but there are some basic things to check.

 

[oldjeep]

Re: 87 3.0 Mercuiser works great! then..........

If you are seeing a running temp of 130 then you have some sort of problem. A 3.0L should run at around 175.

 

[Cuyose]

Re: 87 3.0 Mercuiser works great! then..........

If you are seeing a running temp of 130 then you have some sort of problem. A 3.0L should run at around 175.

Yeah, meant to mention that too, get a heat gun and confirm this temp, it sounds like you might have a faulty thermostat.

 

[maharg]

Re: 87 3.0 Mercuiser works great! then..........

Actually it has a 140 thermostat.

 

[Smacken]

Re: 87 3.0 Mercuiser works great! then..........

I did fail to mention 1 thing. The hose that connects the valve cover to the air filter was nearly plugged with white foamy oil. Is this just the condensation from the motor mixed with a little oil (It didn't seem to burn any oil to speak of). The Thermostat things sounds likes it's worth looking into. Maybe I'm running too cold? There was a new thermostat installed at the beginning of the year, but maybe it's faulty. So maharg, you say it should run about 140?

 

[maharg]

Re: 87 3.0 Mercuiser works great! then..........

Yes, it should run ~140. cant help you on the white foamy stuff, unless you have a closed cooling system.

 

[sltintexas]

Re: 87 3.0 Mercuiser works great! then..........

Actually it has a 140 thermostat.

I agree. book on mine says 143. I guess some years could be different.

 

[sltintexas]

Re: 87 3.0 Mercuiser works great! then..........

I am no expert but this is what I've read a bunch on the forum. If it sits a while and won't start, look down in the carb and see if it looks wet with gas. If you venturi (SP?) are leaking out gass it could make it hard to start. Maybe compare how it looks when you first shut it off to how it looks 30 minutes later... .see if you see any gas slowly dripping out of jets.

I had a similar issue when I rebuilt my carb. I made the proper adjustments to idle mixture, floats, and needle and I'm an "all-go" now.

On the foam in your oil... are you sure you don't have too much oil in there? sure you have the right dipstick? May be worth while to drain your oil, see how much you get out, then see how much you put in.

again, I am no expert..still learnin'

 

[oldjeep]

Re: 87 3.0 Mercuiser works great! then..........

Yes, it should run ~140. cant help you on the white foamy stuff, unless you have a closed cooling system.

A 140 degree thermostat does not mean that the motor runs at 140 degrees , it mean that the thermostat stays closed so the motor can get warmed up to at least 140 degrees. Normal operating temp for a 3.0L is around 175 degrees.

 

[Smacken]

Re: 87 3.0 Mercuiser works great! then..........

I did overfill my oil with about .5L because I wasn't sure what I was in for. That could be my foaming issue. The carb issue is what I was thinking because the carb is quite wet when I go to restart it. Thanks for all your help and I'll post my results if anything changes,

 

[oldjeep]

Re: 87 3.0 Mercuiser works great! then..........

What kind of choke has your carb got on it? If the motor really is running that cold the choke may be on all the time.

Would be worth pulling a couple plugs and see what they look like

 

[sltintexas]

Re: 87 3.0 Mercuiser works great! then..........

A 140 degree thermostat does not mean that the motor runs at 140 degrees , it mean that the thermostat stays closed so the motor can get warmed up to at least 140 degrees. Normal operating temp for a 3.0L is around 175 degrees.

Different years may be different but mine has never gone over 150F.

 

[oldjeep]

Re: 87 3.0 Mercuiser works great! then..........

Different years may be different but mine has never gone over 150F.

Odd. My 1988 and 2005 have always ran at 175. Concensus over at the bayliner board has been that 175 is normal on a number of occassions when people have asked.

I did just look up the thermostat for a 2005 3.0L and it is listed as 160 degrees

 

[Smacken]

Re: 87 3.0 Mercuiser works great! then..........

Electronic Choke and the plugs are a little greasy. I was wondering if the choke might be sticking. I'll explore that a little further, Thanks

 

[QC]

Re: 87 3.0 Mercuiser works great! then..........

A 140 degree thermostat does not mean that the motor runs at 140 degrees , it mean that the thermostat stays closed so the motor can get warmed up to at least 140 degrees. Normal operating temp for a 3.0L is around 175 degrees.

Most thermostats average around 15 degrees between starting to open and fully open. That would mean that around 158 degrees is "normal" operating temp for a 143 stat. Mercruiser did not start using 160 degree thermostats until the mid 90's, so while your boat may operate at 175 (fully open 160 stat) the OPs boat would not unless it was overheating.

The role of a thermostat is minimum operating temperature. They have very little to do with maximum temp other than at it's fully open point the rest of the cooling system needs to be sized to keep an engine from exceeding that temp (fully open temp). So in the OPs case 175 would indicate an overheat This role of the thermostat is true for Cars, Boats, Trucks, Closed cooling or Sea Water cooling.

In the case of the OPs original issue, this sounds a little like a possible vapor lock although not 100% consistent. Do a search in the I/O section and one of the recent posts has a Mercruiser Service letter attached.

I am moving this to the I/O section. We try to keep this section free of engine topics . . .

 

[oldjeep]

Re: 87 3.0 Mercuiser works great! then..........

Please note your source for this information.

Wish I could - the laugh is that of the 3 mercruiser manuals that I've looked at so far they all say "Normal Operating Temperature" and never state a value.

In any event, would you agree that a boat operating at 130 degrees has a problem even if it has a 140 degree thermostat?

 

[vegasphotoman]

Re: 87 3.0 Mercuiser works great! then..........

I did fail to mention 1 thing. The hose that connects the valve cover to the air filter was nearly plugged with white foamy oil. Is this just the condensation from the motor mixed with a little oil (It didn't seem to burn any oil to speak of). The Thermostat things sounds likes it's worth looking into. Maybe I'm running too cold? There was a new thermostat installed at the beginning of the year, but maybe it's faulty. So maharg, you say it should run about 140?

oooo....white foamy oil? might not be good...mine only had clean oil coming in through the breather line to the spark arrestor....no white stuff...

you said the oil was good on the dipstick? no white stuff? wonder if the prev owner changed the oil to hide a internal water leak issue? check your oil again......

140-145degrees is what my 3.0 ran at......ran great but prob a little cold.........I had my 3.0 go to 185 1rst time out (thought it was ok but it started acting up bigtime and ended stalling etc) (greenhorn then) it toasted my internal flapper in the exhaust....had a bad impeller......$300 later it was fixed by the shop...OUCH

I DITTO on the check your choke settings....and make sure you dont have the key on the whole ride home as the electric choke would be wide open after 2-3 minutes or less.....that could definitely cause a hard start.....

 

[IES99]

Re: 87 3.0 Mercuiser works great! then..........

Different years may be different but mine has never gone over 150F.

I would think about carb issues and also water/junk in gas. Do you have a water separating fuel filter?

Not to hijack a thread:

175? 150? My 3.0 runs at just about 160 (for about the last 23 years). If it were to go to 175, I'd be worried about mine.

 

[maharg]

Re: 87 3.0 Mercuiser works great! then..........

Wish I could - the laugh is that of the 3 mercruiser manuals that I've looked at so far they all say "Normal Operating Temperature" and never state a value.

In any event, would you agree that a boat operating at 130 degrees has a problem even if it has a 140 degree thermostat?

Yes, but it is most likely the temp sender, a bad thermo is going to either run really hot or really cold. If its stuck open it will not likely exceed 100, if stuck closed it will just keep going.