86 260HP Mercruiser runs warm
 

I have the same issue as this guy.....

http://www.offshoreonly.com/forums/t...verheat-2.html

At idel the temp will rise but if I bump it into nuetral and give it some gas it will cool down.

I was told to check the transom plate nipple for corrosion, so I pulled off the inner hose today. The nipple is plastic and there was a piece of rubber hose to act as a bushing to fit the inner diameter of the hose....is this normal? I feel probably not, but haven't had a chance to check my manual yet, at work.

Also, this is an 86 engine in my 88 Cobia.

Any help would be greatly appreciated.

take the hose off where it feeds the thermostat housing. run engine. should be nice fat stream of water. at idle u have very little cuz your water pump is shot. if pump is new, check rubber fitting copper tube goes into above pump in upper housing. i had a friend who knew what he was doing but got that bushing halfway down copper tube. engine ran hot forever-till he killed it and sold it back to me!!

So I have to pull the upper housing to check it out?

Got an SEI Alfalfa drive that was missing one of the tubes. Didn't realize it (call it sometimers or trusting) until I test drove boat and it would heat up bad at idle but drop temp as soon as you reved it up a little.

Didn't check with SEI to see if they where supposed to send those or not (did buy full drive which comes in two halves) - just took them off the old busted Alfalfa. Problem solved.

I'll have to look in my service manual.

Thanks for all the help.

Lower housing. You can leave upper on boat. Makes it easier.

Here is one of the biggest hook-ups someone can give you for all this sort of stuff:

http://www.mercstuff.com/howdoi.htm

You are welcome. LOL.

BTW: Page for the Alfalfa water pump DYI is here:
http://www.mercstuff.com/waterpumpinst.htm

What you have back in transom area is normal depending on serial. #. IMO you need a whole complete impeller kit and the bottom base as well. Another wise change but not persay your issue at the moment is to change the water circ pump. A lot of older boats still have the original and run warmer than they should because of it.

Order the complete impeller kit and base, install it correctly as that should clear up your issue.

Can that plastic transom fitting be upgraded at all? I have the same setup and don't really care for that plastic fitting.
Thanks.

I just cured this same issue. The fix was the impeller and housing replacement. After a while, the impeller fins take a set in the curved position and the pump doesn't flow its rated capacity at low RPMs. An interim fix for me was pulling the two small hoses on the top of the thermostat housing which run to the risers and removing the plastic ball check valve there. I gave the springs which hold the balls on their seats a little stretch and reassembled.

I was actually going to grab a new engine circulation pump, because it does look like an original.

That would figure and most likely is the original wc pump. I have no idea why these never get changed out even from a hardship from people not pulling the hose to drain them for winterizations.

You need to change your whole impeller / housing kit and do the bottom base while someone is in there. You have the classic overheating problem with that set up.

Also make sure your water pocket housing assembly is not over heated either as that would have to be changed to. When you pull the lower its up underside in the upper the water tube connects to. Sometimes its wise just to change that as well. Probably the original also.

Not to hijack but I had an 86 Chaparral 235 with twin 260s back in the day. Hard motors to beat.

as long as u have drive split, check seal on top of vert drive shaft. they all rot away. I THINK it may just be an outer seal to keep water out, but...

Well, I tried going out yesterday.....it wasn't good. Hard to start then finally got it going. Then right after I planed out, doing only 35..... The engine just shut off. Then hard to restart. Got her running, then about 10 minutes later, same thing. I had to get towed in....I was pissed to say the least!! The crankcase smells like gas, so I think I'll be replacing the fuel pump.

So I put the garden hose onto the lower unit today. I started the boat up and it warmed up to 200 quickly so I shut her down. I pulled the muffs off and found little pieces of rubber laying on the ground. I pulled the intake screens off and the whole intake was full of little shards of rubber.

Looks like I'll be pulling my lower unit off to change the impeller. Great!!

The guy I bought the boat from said the impeller was new....evidentially he was full of crap!!

Thought you have change this out before you even went to the lake. As I mentioned so in post # 8 about changing the impeller and whole kit so again do yourself a favor change it with a complete kit and the bottom base also as I am sure it just might be blistered from overheating.

Also check the water pocket cover assembly & gasket as you might have burnt that up as well. If you do not do this you will be overheating again in a very short order. I am not trying to kick you in the teeth here but really trying to get my point across here as to what you needed to do.

Also most family rec boaters that are do it yourselfers, do more damage than good working on their own boats. If the old owner changed the impeller with new, I would bet that the reinstall was done incorrectly. When you got towed in what was your temp gauge reading just before your motor shut down ? Anyways good luck.

I will do the whole kit, I mean for a few bucks more it's worth it. When I was towed in I was at 150*. I was only able to run the engine for about 5 to 10 minutes at a time. I think the water pressure caused by the boat moving was assisting the failing impeller.

When I was out in the driveway checking things over, I found the pins in the main harness were all collapsed closed. I could wiggle the harness and cause the engine to sputter. I opened the pins up and plugged the harness back in. The plug actually clicked in place and after I snugged up the clamp I couldn't cause the engine to sputter.

BTW....I should've done the impeller before I went out, so I don't feel like you're riding me. I'm just bummed I let my son down he was really looking forward to that day on the water.

If you haven't done it before, here are good directions:
http://www.mercstuff.com/waterpumpinst.htm

Thanks for the input.