'67 80 hp V4; checking for air leaks?

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rickrodt
1st Vice President AOMCI
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Location: Indianapolis, In

Re: '67 80 hp V4; checking for air leaks?

Postby rickrodt » Tue Jan 16, 2018 5:57 pm

From what I have read, you took a motor off of one boat (short shaft) and installed it on another boat (long shaft). Then you took the boat out and it would not run at high speed, bogged down. Have you ever considered what prop you are running, the load of the boat (weight) and other factors as such as something disrupting the water flow to the lower unit like a keel or depth finder pod directly inline with the lower unit? Secondly, you claimed to have cleaned the carb several times. Did you fully dissemble the carb, taking the high speed jets out, dismateling the venturi nozzles and replace o rings directly under the venturi clusters? How did you line up the clusters as there are special tools to locate them directly in the center of the venturi's? Lastly, a leaking block or air leak would only cause a lean condition, coughing at idle. Usually a bad crankcase seal will have oil coming down the sides of the block. Very seldom will you have a faulty crankcase sealing issue unless someone has taken the block apart and not put it back together with the right sealer. Never rev up the motor in neutral or you can have the "run away" issue as there is no load on the motor or drag to slow the motor down. Those old gearcases had a special prop with a smaller hub that the gearcase to improve performance. You might check to see what prop you are running as I am sure the prop from your short shaft boat will not work with a heavier long shaft one.

Calan
Posts: 109
Joined: Sun Jun 21, 2015 8:42 pm

Re: '67 80 hp V4; checking for air leaks?

Postby Calan » Tue Jan 16, 2018 11:47 pm

OK, so, yes, I was revving it in neutral!
I didn't think I was giving it a whole lot of throttle, but I won't do that again. Learned something.
I hope it wasn't 'cause I got it hot, but I'm going back to the basics which will mean a compression test.

First thing I'll do though is go through and check linkage and synchronization.

Sounds like this is probably not about a leaking gasket, but I'll visually recheck for leaks.

What I did NOT do was use the special tool to line up the high speed nozzles when replacing the orings. I'll buy the tool and put new orings in.
I did fully disassemble the carb, and let it sit in a pinesol / water solution for three days, in a warm environment. Got it really clean, but made no difference. Bought the jet tool; replaced the high speed jets w/ correct NOS parts.

I went through the ignition again after the third failed lake test, and it seems to be right on. I'll put that on the re-check list tho.

I ran it with the hood on, but part of the time with the front door flap hanging open; shouldn't have been air-starved, right? Seemed to make no difference.

Old boat was a 16' aluminum, 450 lbs; this one is a 19' aluminum, 950 lbs. Heavier, but not so very heavy. Modified V-hull that goes about flat, so it shouldn't be all that hard to plane, should it?
The prop is well below the hull; I don't think it's a drag issue.
I tried three tilt settings. They make a lot of props for it; I tried the biggest one, and the smallest one, with almost no difference. I don't know anything, but it feels more like a motor issue than a hull issue. When I back off, I get a brief power surge that I wouldn't expect from drag.

I very much appreciate all the help!
Alan
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FrankR
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Re: '67 80 hp V4; checking for air leaks?

Postby FrankR » Wed Jan 17, 2018 4:38 am

I'm still hung up on the timing/sync issue. Please tell us exactly how you timed the belt. Also, it is possible that the flywheel key is sheared which would throw it out of time. Or the key could be missing out of the distributor pulley (extremely unlikely, but hey who knows?) You certainly seem to have covered all the usual bases. Out of respect, I'm not even going to ask if the plug wires are on the correct plugs.

Calan
Posts: 109
Joined: Sun Jun 21, 2015 8:42 pm

Re: '67 80 hp V4; checking for air leaks?

Postby Calan » Wed Jan 17, 2018 10:24 pm

I'll get a chance at it this weekend, and will post any findings / resolution.
Pulled the flywheel twice now; all was fine both times. No sign of slippage. Tourqued it back down to specs, clean and dry.
Spark wires are NOS, replaced between lake failure #3 and #4. Routed correctly to correct, recent Champion plugs. Replaced the wire from coil to points w/ NOS.
I'll check general timing / sync first. I would be pretty excited to see that the distributor pulley has slipped, which would explain a lot.
As for the venturi tool, please let me know if what I need is pictured below.
Many thanks!
Alan
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tool 2.PNG
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FrankR
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Location: Florida

Re: '67 80 hp V4; checking for air leaks?

Postby FrankR » Thu Jan 18, 2018 6:55 am

Yes, that is a venturi locating tool, but can't tell the size. One size fits 50-60hp another fits 75hp-up. I seriously doubt that is the problem in your case though. It makes a small difference if it is not located, but not to the extent you are experiencing.

FrankR
Posts: 3592
Joined: Tue Mar 10, 2015 6:32 pm
Location: Florida

Re: '67 80 hp V4; checking for air leaks?

Postby FrankR » Thu Jan 18, 2018 8:05 am

The 75-80hp tool measures 1.250" where it fits into the carb bore. I made a couple of them back in the day.
75 hp Venturi Tool 7.jpg
75 hp Venturi Tool 7.jpg (79.89 KiB) Viewed 371 times

fleetwin
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Re: '67 80 hp V4; checking for air leaks?

Postby fleetwin » Thu Jan 18, 2018 5:56 pm

OK, so you have had the flywheel off...Perhaps the belt timing is off. I don't know if there is a different belt timing procedure for the battery distributor vs the mag distributor.

FrankR
Posts: 3592
Joined: Tue Mar 10, 2015 6:32 pm
Location: Florida

Re: '67 80 hp V4; checking for air leaks?

Postby FrankR » Thu Jan 18, 2018 6:09 pm

fleetwin wrote:OK, so you have had the flywheel off...Perhaps the belt timing is off. I don't know if there is a different belt timing procedure for the battery distributor vs the mag distributor.


Yes, different mark to align the distributor pulley with.

Image

JoeCB
Great Lakes Chapter President
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Re: '67 80 hp V4; checking for air leaks?

Postby JoeCB » Fri Jan 19, 2018 12:04 pm

How about the bottom end? somehow coming out of gear? Prop hub slipping? Just a thought...
Joe B

Calan
Posts: 109
Joined: Sun Jun 21, 2015 8:42 pm

Re: '67 80 hp V4; checking for air leaks?

Postby Calan » Sat Jan 20, 2018 7:20 pm

Nice machine work, Frank R! Yours looks better than the one being auctioned.
I have a pretty good eye; I bet my nozzles aren't very far off; glad to hear that's probably not a major factor. I tried two props; don't think they'd both misbehave in the same way, even if both had bad hubs.
I think the belt timing has been OK, despite the flywheel R&R. The belt timing is (I hope) the first pic. I timed the belt with the throttle closed; y'all please let me know if I got that wrong.
I've included pics of the carb with the throttle closed, and wide open. One pic has the distributor fully advanced; hard to see but the linkage is parallel with the triangular boss on the block. The last pic is the linkage, with the throttle wide open. The throttle keeps going after the distributor is fully advanced, (which looks correct, with the spring in the linkage).
The distributor pulley has not slipped on its shaft. I didn't pry it off, but after pulling the points cam, (which was right side up) and nut, I can feel the key in the correct slot with a probe.
Anything else to check, before I reassemble the distributor and move on to the carb?
Many thanks!
Alan
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