95 5.0l OMC Cobra stern drive...overheated 2nd time out

[savedbygrace7777777]

Hello, everyone, i am new here. Just got the boat, and i am a decent amatuer mechanic, but i don't know much about marine engines, or, boats for that matter. 2nd time out, it got up to about 210, i wasnt far from the dock, so i ran the 2 minutes to get there. Shut it off, wouldnt crank when hot to trailer it, but cranked right up when i got home (shut it off immediately), i havent tried to run to it on the trailer with the muffs yet. i am going to check the thermostat. It got too hot running WOT, close to 200, but would cool down quickly at slower speeds and idle...140ish, then it wouldn't cool down.
OK, here is my question...how easily/quickly does it happen and what might i have, melted inside the exhaust system, what should i check for?
Thanks so much in advance for any help!

 

[Lou C]

You have one of the joint venture with Volvo Penta OMCs and as such its the same as a Volvo SX from the same year. The overheating is mostly likely caused by low flow on your raw water pump (engine mounted impeller, the rubber blades wear and take a set and then don't pump enough water). It can also be caused by clogged exhaust elbows, how good is the water flow from your through the hull exhaust? Looks like you are a fresh water boater judging by the painted trailer so clogged exhaust not so likely. What could have burned up:
flappers at the top of the Y pipe if you have one (with the through the hull exhaust, sometimes you have only that so no Y pipe, with switch-able exhaust you might have both). Volvo eliminated the flappers in '99.
rubber exhaust tubes connecting the elbows to the aluminum exhaust pipes leading to the Y pipe and/or thru the transom pipes
in extreme cases...the water pipe gaskets inside the outdrive that seal the pipe that carries water from the lower unit to the upper gear housing
200 degrees is not that bad on the gauge, did you smell burning rubber, hot engine? If not all that may be OK...still need to check...

start with your impeller and housing.

 

[savedbygrace7777777]

The folks that i bought it from said it had a new impeller in the water pump. The gauge maxes at 210, i think...it may have been warmer than 210, but not for long, but, yes, it did smell hot, and a some steam from the exhaust for a short time. i noticed a very faint, smell, not exactly identified as burning rubber, and it was gone within 5-10 minutes of shut down....i continue going through all the related posts....
Thank you so very much for your help!
What should i check first? (i will check the impeller and housing, though supposed to be new).

 

[Scott Danforth]

First....replace the impeller and backflush your whole system

Then pull your drive and check the raw water inlet fitting

Then replace your rubber exhaust hoses

You have lack of flow from either sucking air thru a cracked inlet fitting, or there are bits of the original impeller plugging your system somewhere

 

[zul]

Advise for the future: never start or run the boat when it's out of the water (unless your on the muffs back home). Lots of new boaters like to test fire and rev atop the ramp. Bad idea, could ruin the impeller and lead to overheating.

Also, running WOT for long periods of time is also a bad idea. How long is too long? Hmmm, comes from knowing your boat. And on your first few runs as a new boat owner, you've got to listen, smell and learn. Frustratingly, it takes some time and patients.

Welcome to BOATING !!

 

[savedbygrace7777777]

Thanks, zul. To clarify (and confirm), i only cranked the motor when i got home, i heard it firing, shut it off immediately (ran it for 1.5 seconds, no throttle up)...i won't do it again...muffs only from now on, i was just curious if i had damaged my (new to me) motor! i am going to start checking it out tomorrow.

 

[savedbygrace7777777]

Which of the 3 types of Cobra drives do i have...i think it is the one with the cone clutches based on the hump on the upper...?...sorry to mitigate the post, but i need to know what repair manual to order, and..., i am SUPER NOVICE! ;-)
i must say, i much appreciate all the help so far!

 

[PITBoat]

I believe I got mine from here:

https://www.outboardbooks.com/index.cfm

Svc manual, owner's manual, and parts catalog...

 

[Sparkinator]

You’ve got basically a Volvo Penta SX drive and more than likely a Ford 302 engine. The SX drive is a home run. The Ford engine, is a little less desirable (Ford got out of marine engines in the late 90s). You can still get aftermarket parts for it though. I have the same setup on my boat.

https://boatinfo.no/lib/library.html#

This website will have your drive. Mine is a 95 and is a HU SX model. It will show how to replace the impeller. It is the raw water pump mounted on the engine and belt driven. It will also show how to access and check your thermostat.

Also, you have a back cover missing that you need to replace. It is exposing your shift linkage. The manual for the drive will show you what it looks like.

If you need parts, you can get either omc or Volvo Penta for that year/model for almost anything and either will work.

 

[savedbygrace7777777]

Thank you very much! That helps a ton!

 

[HT32BSX115]

Which of the 3 types of Cobra drives do i have...i think it is the one with the cone clutches based on the hump on the upper...?...sorry to mitigate the post, but i need to know what repair manual to order, and..., i am SUPER NOVICE! ;-)
i must say, i much appreciate all the help so far!

Howdy,

I thought this was covered in another thread....

If you have a 5.0L engine and the boat is a 1995 model, you have one of rthe following model engine/drive packages.

502APHUB 1995
502APHUE 1995
50FAPHUB 1995
50FAPHUE 1995


502ACPMDA 1994
502AGPMDA 1994
50FACPMDA 1994
50FACPMDM 1994
50FAGPMDA 1994
50FAGPMDM 1994

All of the above packages use the OMC Cobra SX/Volvo Penta SX joint venture drives.

You need to ensure that you get the correct manual because most of the manuals are model specific.

Unless someone in the last 25-odd years, changed everything under the hood, you should be able to find one of the above model numbers on the engine.

If your engine has an oil or power steering heat exchanger, check it and the associated hoses from the transom mount to raw water pump and from the pump to the cooler or T-stat housing for debris and/or obstructions.

Regards,


Rick