35 hp evinrude pumps good except when planing?

[a1bigmike]

I have a 1978 35 hp evinrude I have had for about a year now. Just recently got in the water after replacing the boat interior. On the motor I have put new coils due to the condition of the originals, I have rebuilt the carburator due to jets being clogged not allowing boat to reach full throttle, and before any thing I Replaced the water pump impeller and housing and the plastic tube that runs to the bottom of motor housing from the foot because it was cracked and melted in one spot.. Now what is happening is the motor will pump water fine through bleeder from cylinder head and through the two exhaust slits on back of neck when just cruising slowly.. But when trying to plane at full throttle it loses the water flow .. Which in turn equals long boat trips.. Any ideas would be appreciated.. Thanks!-- mike

 

[oldcatamount]

Re: 35 hp evinrude pumps good except when planing?

Can you tell how much of the motor is under water when you're running at WOT? It's possible the motor isn't deep enough when the boat is on plane.

 

[Cofe]

Re: 35 hp evinrude pumps good except when planing?

Sounds like the water intakes are not under water when you hit plane. You can move the tilt pin forward one hole and see how that works. Ideally the anti cavitation plate should be even at the water surface when you hit plane. Hope this helps

 

[F_R]

Re: 35 hp evinrude pumps good except when planing?

I'm thinking not deep enough too. But I'm also thinking about the inherent design flaw. Those motors would not cool within fifty feet of a weed. But probably not the problem here. Perhaps something else is fried from previoius overheating? Upper water tube grommet? Powerhead gaskets?

Or, how about the water pump gaskets? Both there and in good condition?

 

[a1bigmike]

Re: 35 hp evinrude pumps good except when planing?

As far as how deep I Have a tilt trim, no up and down adjustments , and with the size of the boat I found for trying to plane it is better to have on the lowest setting with the pin in the first hole. As for the anti cavitation plate.. Is that the ears on side of motor? This effect water intake? The water inlets are at the bottom of the foot and well submersed during this setting. If i had to estimate aprox. 1/2 the leg from case to foot is submersed.. I thought at first that maybe it was clogged but upon inspection of inlet screens I found nothing there.. I have just replace the tube and all water pump gaskets and housing.. Is there a grommet at the top of the tube that needs replaced? And if a powerhead was bad wouldnt there be other performance issues? thnx mike

 

[Cofe]

Re: 35 hp evinrude pumps good except when planing?

The anti cavitation plate is that wing above the prop. FR is right on about overheats causing gasket/grommet problems. Here is a pic of part of your exhaust housing. Part #115 is the rubber grommet. Part #114 is the water tube guide. Notice the exhaust to power head gasket, sometimes these give problems. When you replaced the impeller, was the old one missing chunks? If it was, the chunks may be lodged in the power head somewhere in a water passage. I would probably check the upper water grommet first, they are subject to exhaust heat, and solidify and crack over time.

 

[a1bigmike]

Re: 35 hp evinrude pumps good except when planing?

Re: cofe- The impeller was aged and cracking but no pieces were missing.. As far as the grommet I never saw this ? When I reinstalled the foot the plastic tube went around the drive shaft side of pump housing this is part # 60. the metal tube Is part # 47. is that the grommet for this tube?. And if this grommet is damaged it would cause the water to quit flowing through head at higher speeds? I would think if pumping through at idle . There would be more volume the faster the engine rpm ? thanks for all info- mike

 

[Cofe]

Re: 35 hp evinrude pumps good except when planing?

There is a identical grommet like part#46 on the top of the water tube. They usually get old and hard and stick up there in the exhaust housing.
After rethinking this, I am beginning to wonder if there is some kind of cavitation problem going on by the water intake screens. It makes sense that the faster you go, the better it should pump water. Is this a short shaft or long shaft motor?

 

[samo_ott]

Re: 35 hp evinrude pumps good except when planing?

It sure sounds like the engine is not low enough or the bottom of the boat is not flat at the back and at speed is pushing the water farther down. Do you have a pis of the engine and back of the boat out of the water?

 

[a1bigmike]

Re: 35 hp evinrude pumps good except when planing?

It is a short shaft motor I assume.. As far as I know it is the original that came on the boat. I dont have any pics right now and boat is in water but plan on pulling back out as soon as I get an idea on where to go with repair. The boat is a 14 foot starcraft with a aluminum hull. V in shape but the bottom rear flattens out by motor.When I put the foot on I remember lining up the tube with the hole inside the casing . I am guessing this is the grommet. I dont think it was that tight of a fit but while supporting entire foot and guiding the other tube with o-rings into place it wasnt that easy to tell. would this grommet cause water flow issues all the time?

 

[Cofe]

Re: 35 hp evinrude pumps good except when planing?

Hey Mike, after rereading this I am wondering if you installed a new grommet in the water pump? It should fit real snug on the water tube.

I am thinking that you may be using your old grommet in the water pump, and the water tube is fitting too loosely. It may stay in place at idle and work fine, but with added pressure at higher speeds, the water tube pushes up and out of the grommet.

Here is about the easiest way I have found to install the lower unit correctly......With the lower unit off. Install the water tube into place in the exhaust tube. Raise the lower unit into position, and install a couple of bolts by a couple of threads. With a flashlight and a couple of screwdrivers, reach into the gap and push the water tube into the grommet in the water pump. Then finish bolting up the lower unit.

 

[a1bigmike]

Re: 35 hp evinrude pumps good except when planing?

hey cofe,
The grommet on water pump is definitely new.. I replaced that with the kit with whole housing and all..the only one which wasnt replaced is the one it slides into up inside the leg housing from engine..? If It is what the tube slides into? You said previously they are they same grommet? This water tube you speak of is the metal pipe right? Not the plastic one with o-rings that goes around the drive shaft .. because thats what I am understanding.. And if was a seal problem with the plastic tube like when cracked previously, what would this cause? thnx

 

[a1bigmike]

Re: 35 hp evinrude pumps good except when planing?

nvm

 

[Cofe]

Re: 35 hp evinrude pumps good except when planing?

Edit:

 

[a1bigmike]

Re: 35 hp evinrude pumps good except when planing?

Last message didnt come through cofe.. please send again.. thnx

 

[a1bigmike]

Re: 35 hp evinrude pumps good except when planing?

can the location of the pin for pitch of the motor be so sensitive as to make this an issue from one height to the next? I had it on the furthest out location then moved to lowest location to help with planing . Didn't notice the problem until I was at the lowest height. But they were only 10 min a piece. could the angle be to steep in the wrong direction? thnx for any info.

 

[a1bigmike]

Re: 35 hp evinrude pumps good except when planing?

Do i need to repost a new thread to get any further help? wtf

 

[scotteam]

Re: 35 hp evinrude pumps good except when planing?

I know that when i take off at full tilt the area behind and around the motor becomes free of water right to the tip of the skeg plate. the motor stops pumping for a few seconds and the prop is clear of water. It than goes back under and starts pumping. If your prop stays out of the water you may need a long shaft and have a short. If you have a long shaft take it to a boat dealer and have them reposition on the transom or you can special order a super long shaft. Places that cater to sailing will have them.

 

[Daviet]

Re: 35 hp evinrude pumps good except when planing?

You don't need to start another post, but you need to ansewer the questions asked for anyone to help you. Ansewer post #2.

 

[a1bigmike]

Re: 35 hp evinrude pumps good except when planing?

Ok.. the anti cavitation plate does not break the surface of the water. I took out today again to see if I can get a little more info as to what is happening and what I notice is the motor runs fine with a light mist coming out exhaust ports until I get to the end of the river aprox. 45 min no wake zone. Then when I get to the gulf it has started to steam a little coming out of exhaust ports and the water coming out is too hot to touch. The water coming of the pee hole is not hot at all.. But still runs into the same scenario if you try and go full throttle.. you lose the water prime is what it seems, but as soon as i back off throttle it starts to pump through the pee hole again .. but does steam when running around 1/2 throttle. but never loses water ? does this help at all..