Evinrude Big Twin 40hp Not Pumping Water On Plane

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Author Topic:   Evinrude Big Twin 40hp Not Pumping Water On Plane

Sojo81007 posted 06-27-2014 07:15 PM ET (US)
Finally got my Evinrude Big Twin running well after last year' s disasters :) It starts quickly and runs smoothly and pumps water (has new impeller) really well....until the boat ('68 Whaler 13) starts coming out of the hole, the water coming out the back (no telltale) stops and won't start until I bring the boat off plane. Any ideas? It was doing something similar last season, but would only refuse to pump water mid-range and would pump fine at WOT and off plane.
THANKS!

contender posted 06-27-2014 09:09 PM ET (US)
Water pump. (did you replace the entire water pump or just the impeler, and did you used an after market part for the water pump?) Two things you never do, ONLY use a factory waterpump and housing, and the primer bulb. Also check your pick up in the lower unit, If you drop the lower unit I would blow out the intake tube in the lower unit could be a part blockage (sometimes the plastic in the lower unit breaks a clogs the tube or the tube could be bad as well)...good luck
Sojo81007 posted 06-28-2014 08:38 AM ET (US)
I did replace on the impeller. I'm wondering if the housing could be worn...or possibly a tube is not inserted firmly enough to a grommet so when it's under water it can pump fine, but once it's out it's sucking air.
I don't have many opportunities to get out on the water this summer so I'm hoping to get this small (hopefully) issue fixed!
Sojo81007 posted 06-28-2014 10:28 PM ET (US)
Before I drop the LU I'm going to add a tell-tale, something I've been wanting do to for some time. I found a FAQ over at iboats that talks about how to tap the water jacket etc. It looks pretty straightforward, but I'm confused about the fitting that's recommended. The part number recommended is
Sierra # 18-3290, which appears to be a plastic fuel fitting. Certainly that can't correct! All of the pictures I've seen of added tell-tales have been brass, which is what I'd like to do.
Sojo81007 posted 06-28-2014 10:28 PM ET (US)
Before I drop the LU I'm going to add a tell-tale, something I've been wanting do to for some time. I found a FAQ over at iboats that talks about how to tap the water jacket etc. It looks pretty straightforward, but I'm confused about the fitting that's recommended. The part number recommended is
Sierra # 18-3290, which appears to be a plastic fuel fitting. Certainly that can't correct! All of the pictures I've seen of added tell-tales have been brass, which is what I'd like to do.
sosmerc posted 06-29-2014 05:45 PM ET (US)
Are we sure you have the correct shaft length engine for the boat?
adlert posted 07-02-2014 12:36 PM ET (US)
Also, are you sure you actually have a problem with water flow and/or the engine running too warm on plane? I can't remember for certain about the Big Twin, but certainly some of the older OMC engines did not pump much (if any) water out of the exhaust relief exit hole(s) that you are focused on. I know of no older OMC engines that didn't pump a fair amount of water out those openings WHEN WARM (thermostat open) and at idle. But at higher hull speeds most, (if not essentially all) of the exhaust and cooling water exits the exhaust snorkel located under the anti ventilation plate and behind the prop on some OMC engines at certain speeds.
Some of my older OMC engines have pumped little to no exhaust and water out of the exhaust relief passages when at speed, but checking the exhaust manifold plate and cylinder head temps when on plane revealed that in fact, all was well.
sosmerc posted 07-03-2014 01:32 AM ET (US)
It seems like ions ago, but some of my first outboards were 1958 vintage 35hp "big twins". It always used to bother me when I couldn't tell exactly how the water pump was doing....so I always added a "pee hose" off of the water jacket on the cylinder head.....and then I had the peace of mind seeing that constant stream of cooling water.
Sojo81007 posted 07-14-2014 03:55 PM ET (US)
I tapped the head near the top cylinder as that seemed the best location on my particular unit. I routed the hose through the hole already drilled toward the rear of the housing and it pumps well at all speeds. Peace of mind!
THANKS!

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Author	Topic: Evinrude Big Twin 40hp Not Pumping Water On Plane
Sojo81007	posted 06-27-2014 07:15 PM ET (US) Finally got my Evinrude Big Twin running well after last year' s disasters :) It starts quickly and runs smoothly and pumps water (has new impeller) really well....until the boat ('68 Whaler 13) starts coming out of the hole, the water coming out the back (no telltale) stops and won't start until I bring the boat off plane. Any ideas? It was doing something similar last season, but would only refuse to pump water mid-range and would pump fine at WOT and off plane. THANKS!
contender	posted 06-27-2014 09:09 PM ET (US) Water pump. (did you replace the entire water pump or just the impeler, and did you used an after market part for the water pump?) Two things you never do, ONLY use a factory waterpump and housing, and the primer bulb. Also check your pick up in the lower unit, If you drop the lower unit I would blow out the intake tube in the lower unit could be a part blockage (sometimes the plastic in the lower unit breaks a clogs the tube or the tube could be bad as well)...good luck
Sojo81007	posted 06-28-2014 08:38 AM ET (US) I did replace on the impeller. I'm wondering if the housing could be worn...or possibly a tube is not inserted firmly enough to a grommet so when it's under water it can pump fine, but once it's out it's sucking air. I don't have many opportunities to get out on the water this summer so I'm hoping to get this small (hopefully) issue fixed!
Sojo81007	posted 06-28-2014 10:28 PM ET (US) Before I drop the LU I'm going to add a tell-tale, something I've been wanting do to for some time. I found a FAQ over at iboats that talks about how to tap the water jacket etc. It looks pretty straightforward, but I'm confused about the fitting that's recommended. The part number recommended is Sierra # 18-3290, which appears to be a plastic fuel fitting. Certainly that can't correct! All of the pictures I've seen of added tell-tales have been brass, which is what I'd like to do.
Sojo81007	posted 06-28-2014 10:28 PM ET (US) Before I drop the LU I'm going to add a tell-tale, something I've been wanting do to for some time. I found a FAQ over at iboats that talks about how to tap the water jacket etc. It looks pretty straightforward, but I'm confused about the fitting that's recommended. The part number recommended is Sierra # 18-3290, which appears to be a plastic fuel fitting. Certainly that can't correct! All of the pictures I've seen of added tell-tales have been brass, which is what I'd like to do.
sosmerc	posted 06-29-2014 05:45 PM ET (US) Are we sure you have the correct shaft length engine for the boat?
adlert	posted 07-02-2014 12:36 PM ET (US) Also, are you sure you actually have a problem with water flow and/or the engine running too warm on plane? I can't remember for certain about the Big Twin, but certainly some of the older OMC engines did not pump much (if any) water out of the exhaust relief exit hole(s) that you are focused on. I know of no older OMC engines that didn't pump a fair amount of water out those openings WHEN WARM (thermostat open) and at idle. But at higher hull speeds most, (if not essentially all) of the exhaust and cooling water exits the exhaust snorkel located under the anti ventilation plate and behind the prop on some OMC engines at certain speeds. Some of my older OMC engines have pumped little to no exhaust and water out of the exhaust relief passages when at speed, but checking the exhaust manifold plate and cylinder head temps when on plane revealed that in fact, all was well.
sosmerc	posted 07-03-2014 01:32 AM ET (US) It seems like ions ago, but some of my first outboards were 1958 vintage 35hp "big twins". It always used to bother me when I couldn't tell exactly how the water pump was doing....so I always added a "pee hose" off of the water jacket on the cylinder head.....and then I had the peace of mind seeing that constant stream of cooling water.
Sojo81007	posted 07-14-2014 03:55 PM ET (US) I tapped the head near the top cylinder as that seemed the best location on my particular unit. I routed the hose through the hole already drilled toward the rear of the housing and it pumps well at all speeds. Peace of mind! THANKS!