Will this work with my 4 hp

Don Hansen · Jan 18, 2013

My 1974 4 hp threw a rod last, year putting a hole a little smaller than a dime in the crankcase wall. Here's what I'm planning on doing. I shaped a piece of 0.030 brass to cover the hole. After I clean and sandblast the crankcase I plan to glue the brass patch to the crankcase with J B Weld. Will that work? Did I missed something?

DLH

Robj · Jan 18, 2013

Re: Will this work with my 4 hp

Why don't you just find a new short block? That is the right way to fix it IMO. Remember the crankcase needs to be air tight. Send me a pm if you need one, there may be one hiding in my shed somewhere.

Silvertip · Jan 18, 2013

Re: Will this work with my 4 hp

Brass that thickness will flex due to the pressure/vacuum pulses in the crankcase. That flexing will sooner or later very likely pop the piece loose. If space permits, and a hole that small, you can shape a piece of aluminum a bit larger than the hole, Drill and tap four holes for four #10-32 stainless machine screws. Fashion a gasket for the plate, coat it with Permatex aviation forma gasket and attach the plate. Go boating.

boobie · Jan 19, 2013

Re: Will this work with my 4 hp

Just put on plenty of J B Weld. Don't know if it will work until you try it.

the machinist · Jan 19, 2013

Re: Will this work with my 4 hp

I have patched them by heliarc welding a aluminum patch in.

boobie · Jan 19, 2013

Re: Will this work with my 4 hp

That's a better idea !!!

Don Hansen · Jan 20, 2013

Re: Will this work with my 4 hp

Here's a picture of the hole. The picture was taken before I filed the area next to the bolt and dowel pin holes flat so I would have more surface for what ever type of patch I used. If you look close you will see that the patch not only has to fit around that rib but it has to have a bubble in it for crankshaft/rod cap clearance. Took me 4 tries before I was happy with the results

I thought about having it welded but have read too many horror stories about welding cast aluminum. I discarded the screw idea, I was going to use 4-40 screws, because of the shape of the patch. It has a 90 degree bend it. As far as the 0.030 brass flexing, I don't think there's that much pressure in the crank case because the fuel pump is able to take it. I did some testing of the J B Weld. I heated it to 400 degrees with no effect. I applied it to a clean and sandblasted piece of the 0.030 brass and it held up pretty well while I flexed the brass. I had to actually put a bend in the brass before the J B weld failed.

I PMed Robj asking him what he would need for a new short block if he has one. I'll wait until I hear from him before I make a decision.

I know that the crankcases and crankshafts were the same from 1969 to 1976 or was it 77.

Don Hansen

the machinist · Jan 20, 2013

Re: Will this work with my 4 hp

With your patch & a generous amount of JB Weld, I see no problem. Your concerns on welding this alumium are unfounded IF the welder does not contaminate the surface at the start of the process. This is pretty easy to weld IF you do not overheat it.

Don Hansen · Jan 20, 2013

Re: Will this work with my 4 hp

the machinist said:
With your patch & a generous amount of JB Weld, I see no problem. Your concerns on welding this alumium are unfounded IF the welder does not contaminate the surface at the start of the process. This is pretty easy to weld IF you do not overheat it.

The thickness of the crankcase wall has to make a difference? That wall is only about 1/8 thick in places. Seems like it would be easy to overheat it.

I have to allow clearance for the head of a screw but I was thinking of not only gluing the patch but also adding some to the outside for reinforcement. As I mentioned, I plan on sandblasting both the crankcase and the patch to give the J B Weld something to get a hold of.

Don Hansen

Don Hansen · Jan 27, 2013

Re: Will this work with my 4 hp

Here's a picture of my repairs. If you look at my original pictures you can make out a crack and one of the holes I drilled to stop it from traveling in the pocket above the side with the hole. In this picture you can see both of my brass patches I made and are now glued to the crankcase with J B Weld. Turned out pretty good I thought.

DLHhttp://forums.iboats.com/attachment.php?attachmentid=180054&d=1359326162&thumb=1&stc=1

nwcove · Jan 27, 2013

Re: Will this work with my 4 hp

that does look like a nice clean job...good work Don.

boobie · Jan 27, 2013

Re: Will this work with my 4 hp

Super job. Let us know how it turns out when you get it running.

Don Hansen · Apr 27, 2013

Re: Will this work with my 4 hp

Well the weather in Wisconsin finally was warm enough to test my repair. Ran the motor in a garbage can for a couple of hours on gas with double oil to help break-in the new crank and connecting rod. Couldn't run the motor more than half speed but it sure sounded sweet. Can't wait until I can get it on the water to give it a proper break-in. Only time will tell if my patches hold.

BTW I'm adding a tell tale nipple, with a 1/8 inch hole, to the exhaust plate where it covers part of the water jacket. I mentioned this in another post but I'll ask again. Does anyone see something wrong with doing this?

DLH

boobie · Apr 27, 2013

Re: Will this work with my 4 hp

No. What part of Wisconsin are you from ??

Don Hansen · Apr 27, 2013

Re: Will this work with my 4 hp

boobie said:
No. What part of Wisconsin are you from ??

West Allis. Have lived here all my life, 69 years. Why do you ask? I see you are in Florida.

I have to wait for a new gasket to arrive before I can install my new plate. I used 1/4 inch aluminum stock for the plate along with a brass shoulder bolt to make the nipple.

Rick. · Apr 27, 2013

Re: Will this work with my 4 hp

Way to go Don. I missed your post about this earlier, but would not have imagined what you've done. You are a craftsman. Are you going to run a richer fuel mix now? LOL. Best of luck. Rick.

boobie · Apr 27, 2013

Re: Will this work with my 4 hp

I orginally came from the Minocqua-Woodruff area, but finally got smart and moved here, LOL

kodibass · Apr 28, 2013

Re: Will this work with my 4 hp

you can get a welder to fix that with aluminum of the correct thickness, But it might be cheaper to buy a used one on e-bay, the salvage yards listed here on iboats.

Don Hansen · Apr 28, 2013

Re: Will this work with my 4 hp

Rick. said:
Way to go Don. I missed your post about this earlier, but would not have imagined what you've done. You are a craftsman. Are you going to run a richer fuel mix now? LOL. Best of luck. Rick.

I was running both my 4 hp and my 1980 35 hp at 50 to 1 but because of the E10 gas I think I'm going to run 40 to 1. I've already installed one of those Racor filter/water separators just to play it safe.

DLH

Rick. · Apr 28, 2013

Re: Will this work with my 4 hp

Don Hansen said:
I was running both my 4 hp and my 1980 35 hp at 50 to 1 but because of the E10 gas I think I'm going to run 40 to 1. I've already installed one of those Racor filter/water separators just to play it safe.

DLH

I've seen many posts about our 4HP's having to use 24/1 due to the lack of needle bearings (or may be the presence of needle bearings I don't remember) Anyway over time I started mixing richer for the 4HP. Now I'm at 30/1 full synthetic. I've experienced no problems at all with the richer mix so I will keep it up. I still have my 95-40HP. on VRO and it seems to use less than a 50/1 mix over all, at least in my mind it does. I've never tried to calculate the actual oil use on it. Rick.

Will this work with my 4 hp

Petty Officer 1st Class

Lieutenant

Supreme Mariner

Supreme Mariner

Senior Chief Petty Officer

Supreme Mariner

Petty Officer 1st Class

Attachments

Senior Chief Petty Officer

Petty Officer 1st Class

Petty Officer 1st Class

Attachments

Admiral

Supreme Mariner

Petty Officer 1st Class

Supreme Mariner

Petty Officer 1st Class

Captain

Supreme Mariner

Master Chief Petty Officer

Petty Officer 1st Class

Captain