Pontoon Boat & Deck Boat Forum

Hey all - I'm getting ITCHY to get out on the water! Tomorrow's temps are supposed to be in the low 70's and sunny so I think I'll play hooky from work and go out! Water temp is still in the high 40's so no swimming for us or the dogs but a cruise up the river would be nice.

So this afternoon I started my I/O on muffs and let it warm up. She went to 160, 180 and then about 190 where it kicked down to 160 quite rapidly. I'm guessing this was the thermo piece opening up and letting more water in, correct? I let it run for another couple minutes and it stayed at 160-165 or so.

Is that about the correct operating temps for a Mercruiser 3.0? I had the "better muffs" with the dual inlet and had them sealed completely around the intake so I know it was getting enough water. But just wanted to check!

Did you see the light and bimini upright pics I posted?

160 is about where both my Starcraft and the Party Cruiser run at. Yes, that was your thermostat kicking in. If it ever goes to 220, shut her right down....

lakerunner wrote:Did you see the light and bimini upright pics I posted?

Nope I did not - is it in another thread? I've been slacking on browsing lately.

badmoonrising wrote:160 is about where both my Starcraft and the Party Cruiser run at. Yes, that was your thermostat kicking in. If it ever goes to 220, shut her right down....

Sweet - thanks man.

They are in your polishing toons thread

ya.. my 3.0 runs around 160-170.
Never seen higher then 170....

WaltF wrote:ya.. my 3.0 runs around 160-170.
Never seen higher then 170....

Took it out on the river for the first long run today! Went about 1500rpm's up about 10 miles, going WOT every now and then. Stayed steady at 165f the entire time.

I'll tell you what - we passed a lot of fishing boats and I couldn't help but put-put my "big azz 'toon" by them and then just as we got down river I'd crank it up. I saw the looks on a few guys face when they saw this giant pontoon jump the bow out of the water and get up on plane... They were surprised as I was!

Sweeeet!

Ya we love our toon too!
The 3.0 is a solid engine and with <5 in the toon, it gets along pretty dern good even w/o the strakes!

Course i'd like to have a set TIG'd on..... maybe someday,...

assuming your water pump is in the lower unit i would pull it
and look at the impeller. temp issues after storage can mean
a flat spot in the impeller and maybe shedding a blade.
with the lower unit pulled, i would replace the impeller,
pump housing, seals, driveshaft o-rings, and while it was
apart i'd put in a new pump base, too. doesn't cost much.
you're supposed to do the impeller and pump housing every
two years. if you shred an impeller it can take years to
locate all the pieces in your cooling system. and occasionally
they can block flow and cause overheating.

if your water pump is on the engine then never mind.

The 3.0 has both, lower unit water pump and belt driven on the motor.

right, but the belt driven engine pump is the
regular motor water pump. i should have
said "water pick-up pump". i think with some
later model merc sterndrives the pick-up
pump is up by the engine. or maybe that's
volvo, i don't remember. on my sterndrive
(and most merc's, i think), the pick-up
pump is a plastic housing pump with a rubber
impeller, and the whole thing is located near
the bottom of the lower unit. when that
impeller shreds, pieces of it spread throughout
the cooling system and cause problems later on.
i might go to the blue "run dry" impeller that the
navy uses. it costs a little more, but if the pump
is ever run dry the impeller doesn't immediately
fail due to overheating. it delivers a little less
cooling water flow, but i've got plenty of gpm.
anyway, the way beermunk's temps went up
on the first run of the year and then dropped
sounds like either a late acting thermostat or
a flat spot on the impeller.

FloterBoter wrote:right, but the belt driven engine pump is the
regular motor water pump. i should have
said "water pick-up pump". i think with some
later model merc sterndrives the pick-up
pump is up by the engine. or maybe that's
volvo, i don't remember. on my sterndrive
(and most merc's, i think), the pick-up
pump is a plastic housing pump with a rubber
impeller, and the whole thing is located near
the bottom of the lower unit. when that
impeller shreds, pieces of it spread throughout
the cooling system and cause problems later on.
i might go to the blue "run dry" impeller that the
navy uses. it costs a little more, but if the pump
is ever run dry the impeller doesn't immediately
fail due to overheating. it delivers a little less
cooling water flow, but i've got plenty of gpm.
anyway, the way beermunk's temps went up
on the first run of the year and then dropped
sounds like either a late acting thermostat or
a flat spot on the impeller.

What's it like to change out the thermostat?

2 bolts and undoing 3 hoses, easy. It's right on top and easy to get to. All you need is a flat blade screw driver to remove the hoses and a 1/2 inch socket. With p/s there is 2 gaskets, without, 1.

Curious...
How hard is it to replace the Impeller on the 3.0?
Where the heck is the thing?