1971ish omc stringer and freshwater cooled 350

[humboldtbrad]

I just picked up this boat and the po said he thought it needed a jasco pump now that confuses me because it is freshwater cooled I'm kinda new to a system like this so please bear with me

 

[Boomyal]

Re: 1971ish omc stringer and freshwater cooled 350

Jasco makes bilge blowers and maybe bilge pumps. I don't know of any water cooling pumps that they would make. In fact, I am not aware of any remote cooling pumps that would have been used with OMC Stringer drives.

 

[humboldtbrad]

Re: 1971ish omc stringer and freshwater cooled 350

Well maybe I'm calling it the wrong thing. possibly an impeller located in the out drive I guess it could be there to circulate water over a heat exchanger?

 

[Howard Sterndrive]

Re: 1971ish omc stringer and freshwater cooled 350

there's an impeller in the sterndrive. You'll see lots of references on the web to an aftermkt kit that services OMC stringer impellers from 1964-1985. Although that isn't true, that will be the kit you need.
Your local Evinrude dealer will have the OEM kit and you can get an original factory service manual from ebay or Ken Cook publications (outboardbooks.com)

 

[Boomyal]

Re: 1971ish omc stringer and freshwater cooled 350

Yes, the impeller in the upper drive, circulates the water thru the heat exchanger and back out thru the exhuast manifolds. The engine water pump then pumps the coolant thru the other side of the heat exchanger, via the thermostat, then thru the rest of the engine and back to the heat exchanger.

The best way to test the drive pump is to have the boat in the water. While the engine is running, diisconnect the hose coming up from the intermediate housing, where it connects to the heat exchanger and watch the stream of water. Even at an idle, it should be a steady flow of water, with out a lot of spitting. Have someone increase the RPM up to about 2K rpm and the flow should noticeably increase.

That hose connection is the same one that you would disconnect when winterizing the boat. I always re-attach it using a silicone grease, so that it comes on and off easily.

Some say that that impeller should be changed as much as annually. My experience is that the OMC impeller, which is 3 or better times bigger than a Merc impeller, lasts reliably for many a year. (that is assuming that you do not drag your outdrive thru the sand or muck.

 

[humboldtbrad]

Re: 1971ish omc stringer and freshwater cooled 350

well i just spoke to a local shop and he said it would cost me around 1k to have it changed and I'm thinking that's bs.
is there any way to test it without putting it in the water?

 

[Boomyal]

Re: 1971ish omc stringer and freshwater cooled 350

well i just spoke to a local shop and he said it would cost me around 1k to have it changed and I'm thinking that's bs.
is there any way to test it without putting it in the water?

That does sound a bit high, IMHO. As to testing, without a teardown and visual inspection, submersing the outdrive is the only way to tell if it is capable of pumping sufficient volume. Using muffs or if you have the flush fitting on the trunnion, will force water up thru the drive. This would not tell the pump's capability.

 

[southkogs]

Re: 1971ish omc stringer and freshwater cooled 350

... $1k to replace the impeller on an OMC Stringer? :faint2: Chances are the marine tech doesn't want to work on OMC, I've actually had guys who wouldn't even talk to me.

Get a manual. If I can do it, you can do it. Frankly, if I can do it, your 5 y.o. daughter can do it I'd opt to just change the thing anyway. Getting the drive off a '71 is a cake walk, and the whole project should be pretty quick.

Otherwise, Boom's got it right. Take it over to the lake, launch and tie up to the courtesy dock and let it idle up to temp there.

 

[humboldtbrad]

Re: 1971ish omc stringer and freshwater cooled 350

Well I guree to the water I go I'm going to do it in humboldt bay its about 15 min from my house

 

[Howard Sterndrive]

Re: 1971ish omc stringer and freshwater cooled 350

common sense says to change the impeller on any new-to-you boat. You need to grease the splines in there too. There's probably 20 threads on this board where people ignored the impeller in their stringer drive, and the shaft splines stripped.

 

[humboldtbrad]

Re: 1971ish omc stringer and freshwater cooled 350

Well I'm going to do the test and if all is well then great. If not then ill tear in to it

 

[humboldtbrad]

Re: 1971ish omc stringer and freshwater cooled 350

so I finally got out to test the boat and the impeller is working great. I went for a 2 hour cruise and didn't encounter any problems except my trim tabs aren't working but i guess some issues are expected.
thanks for the help.

 

[humboldtbrad]

Re: 1971ish omc stringer and freshwater cooled 350

i took the boat out for a long run yesterday and at full throttle for 15-20 minutes it started to get hot but at anything less than full throttle i have zero problems is the impeller not working completely? maybe blocked water passages in the exhaust manifold restricting flow? also when it was hot the exhaust seemed to have steam in it but it runs great so I'm not sure if I'm just over worrying

 

[Boomyal]

Re: 1971ish omc stringer and freshwater cooled 350

The higher the rpm/speed, the higher the heat generation. Whereas a compromised/degraded impeller may keep up with demand at low load, it may run short higher up. I really doubt that you have any blockage anywhere except for certain possibilities in your exhaust manifold exits. What style of mani's do you have. Maybe even post a picture.

This is a good case for having an infrared heat gun. I don't like the sound of 'steam'. When you say 'fresh water cooled' are meaning you have a heat exchanger? If so, are the manifolds included in the loop?

I have a heat exchanger on my 302 with logstyle exhuast manifolds. Water comes up from the outdrive, thru the heat exchanger and back out through the exhaust manifolds. There is a restrictor gasket between the logs and the exit elbow to slow down the water flow on exit.

It maybe that your heat exchanger (if you have it) is crudded up and needs to be disassembled and rodded out.

 

[humboldtbrad]

Re: 1971ish omc stringer and freshwater cooled 350

it sounds like we have the exact same system

 

[Howard Sterndrive]

Re: 1971ish omc stringer and freshwater cooled 350

grease your swivel bearing on the outdrive. The grease will seal the water supply passages from exhaust gases.