1984 Evinrude 25hp mounting

[jimmbo]

Looking at the 1st pic, it looks like it is still too deep in the water.
As for the revs up without a linear increase in speed. Was it an actual increase in rpm, or just a lot more Carb Noise?

 

[shimanok2]

jimmbo, I was fearful of mounting the jack plate and the motor being too high. Currently the CAV plate is ~1/2" below. I could try shimming it up to make it even. If it needs to go higher I'd likely remove the jackplate and move it up a set of hole. I believe they're spaced 1".

It sounded like the revs were up. Wish I had checked the tach while doing this.

 

[jimmbo]

If the revs are going up but no speed increase, then the Prop could be losing it's bite. That Engine has a gear case and prop lineage that leaves a lot to be desired when it comes to performance. Few, if any, of the props for it have any amount of Rake and/or Cupping, both of which help keep a prop hooked on to the water.

 

[shimanok2]

By "losing it's bite" do you mean spinning relative to the inner hub section?

Regarding lack of performance, are you saying that this should be expected?

 

[jimmbo]

No, I was referring to its grip on the water

The Gear Housing shape and the Propeller designs for that engine leave a lot to be desired when it comes to performance. The Props have Blades that have no Rake, and no cupping.

 

[tphoyt]

Did you do any filing to that prop?
The leading edges look like they have been shaped somewhat. In for very first post the prop doesn’t look like it was in great shape to start with. You could be getting some cavitation.

 

[shimanok2]

Thanks Jimbo, I guess I should have been more specific. Is it worth investigating a spun hub? Seems they're pressed together but I can press them apart for inspection if you think it's worth while.

Not that I'm going to buy another outboard because of this, but would a 10, 20, etc. year newer version have a better gearcase and prop design?

For reference, I had myself (220lbs), both kids (60lbs each), 6 gallons of gas, anchor and a small cooler. Also forgot I had 100lbs in the bow from when I was out by myself a couple weeks ago. Zero issues getting on plane, I'm wondering if the 25hp is overkill and if a 15 or 20hp would be better since they're lighter (maybe only ~20lbs???). This Mirrocraft had a rather poor DIY console on it when I bought it, since removed. The rear bench seat is rather deep (bow --> stern), kinda of like it's meant to sit forward more for a console. My wifes going to kill me.

 

[shimanok2]

Did you do any filing to that prop?
The leading edges look like they have been shaped somewhat. In for very first post the prop doesn’t look like it was in great shape to start with. You could be getting some cavitation.

I haven't toughed the prop, aside from removing it for rebuilding the lower unit. Is filing a common practice?

I didn't have a chance to make it to the marina at lunch today so will try tomorrow. Even if it's just for figuring out if it's close to being the correct prop, pitch, etc.

 

[jimmbo]

In the late 80s the 20 and 25 hp engines were fitted with the Midsection and Gearcase that previously was used exclusively by the 35hp. It was a more Hydrodynamic shape, had larger gears and a Prop designed with blades that had more Rake and often some cupping.
We had a couple of Mirrocraft 14 ft Deep Fisherman. One had a 79 25hp, the other a 1980 35hp. The Boat with the 25 had a 15" Transom, the one with the 35 was a 20" model.

 

[jimmbo]

deleted. Duplicated post

 

[tphoyt]

I was just wondering you had done a lot of filing and possibly changed the shape.
Filing out small nicks is common but to do a proper job if it’s bent it should be done at a prop shop. It’s hard to tell from the photos but it looked like the leading edges were bent up which would cause it to create air around the prop.
To check and see if it’s slipping you can mark the prop and the hub with a marker and check the marks after running it and see if they are still aligned. If not then it’s slipping. It can be very difficult to spin this by hand unless it’s been severely spun which doesn’t seam likely in your case.

 

[shimanok2]

In the late 80s the 20 and 25 hp engines were fitted with the Midsection and Gearcase that previously was used exclusively by the 35hp. It was a more Hydrodynamic shape, had larger gears and a Prop designed with blades that had more Rake and often some cupping.
We had a couple of Mirrocraft 14 ft Deep Fisherman. One had a 79 25hp, the other a 1980 35hp. The Boat with the 25 had a 15" Transom, the one with the 35 was a 20" model.

View attachment 366410

Very informative! I do believe mine (1984) was a transition year as I've seen several references to the 79-84 as being a non-thru-hub exhaust and the 85-90 something as being thru-hub. The main water intake is behind the prop too so muffs can't be used. I replaced the screen and then tapped the hole so a bolt could be used to hold it in place. I thought about making a special plate with a hose connection (to replace the water bypass cover) for running the motor out of the water but got lazy.

That appears to be the same boat I've got. I've got a 1981 F-4614 which I believe is a deep fisherman. Was the rear bench seat on yours like 16-18" deep?

 

[shimanok2]

I was just wondering you had done a lot of filing and possibly changed the shape.
Filing out small nicks is common but to do a proper job if it’s bent it should be done at a prop shop. It’s hard to tell from the photos but it looked like the leading edges were bent up which would cause it to create air around the prop.
To check and see if it’s slipping you can mark the prop and the hub with a marker and check the marks after running it and see if they are still aligned. If not then it’s slipping. It can be very difficult to spin this by hand unless it’s been severely spun which doesn’t seam likely in your case.

I brought the prop with me to work today so it's sitting on my desk. I don't see any filing and it doesn't appear bent, although I've never really looked at a prop in much detail before.

We're leaving Saturday for vacation and bringing the boat. Unfortunately I won't have enough time this week to trial this but can once we get to the lake. I may try to pick up a new prop/hub just in case I find it is slipping. Easy swap in the water. I will also check RPMs too.

 

[jimmbo]

It had 3 benches, and a Triangular Wedge Seat at the Bow. We them till about the mid 90s, when I think my brother sold them. Used to use them on a Nasty Lake

 

[shimanok2]

It had 3 benches, and a Triangular Wedge Seat at the Bow. We them till about the mid 90s, when I think my brother sold them. Used to use them on a Nasty Lake

View attachment 366428

Mine only has the 3 bench seats as well but the rear bench is much deeper than the front 2. We'll get swells like that on the bigger lakes (namely Winnipesaukee) but it takes a special day. No way I would want to be out on that in the 14' either.

 

[shimanok2]

I don't know how to link to a specific post in a thread but found # 18 here to be very informative. Sounds like this a continuation of what you posted above jimboo. Maybe the motor isn't too low then because of the gearcase design?

1975 25 hp evinrude

Finally got to take my boat out today. it's a 1448 welded jon. 20" transom with a long shaft 25 hp. when i am going down the lake at full throttle there is a lot of spay coming up the transome and into the boat.I trimmed the motor all the way out,meaning the 4th hole away fom the boat, but still...

forums.iboats.com

 

[jimmbo]

Mine only has the 3 bench seats as well but the rear bench is much deeper than the front 2. We'll get swells like that on the bigger lakes (namely Winnipesaukee) but it takes a special day. No way I would want to be out on that in the 14' either.

It was about like that, the Day I flipped the 10 or 12 foot back in 1976

 

[shimanok2]

I hope that wasn't part of the plan!

 

[jimmbo]

Wasn't part of the Plan, but fecal matter happens. I was fairly close to shore and the water wasn't more than 3 1/2 ft deep. I stood up and the boat was still capsized, I remember seeing the Prop spin a few more times then quit. I flipped boat back over and retrieved the Gas Tank, Anchor and Oars, and headed for shore. I pulled the bow out as far as I could,and then removed the engine cowl, a fair bit of water spilled out. I tried the recoil and the engine did rotate. So after about 10 pulls it fired up. I then bailed a bit more water out and then refloated the boat kept the motor running while I continued bailing. I then got back in pulled the drain plug and headed home. When I got home I anchored the boat where the engine could remain down and left it running, and then I proceeded to fill a 55 gal drum. I then transferred the motor the drum and left it running for about an hour. That motor poor little 5 1/2 got dunked two more times, was overheated to where the paint turned brownish, was run without oil in the gearcase for a few days. It was still being used 15 yrs later. I was 16 at the time and didn't tell the old man about the incident for about 5 or 6 yrs.

 

[shimanok2]

Yes it does. You survived, the motor clearly kept going and I assume the boat did as well. Call that a win!

A friend of mine dunked his 15hp in the river one year. Had the safety loop on so it killed it before getting into too much water. Pulled it up by the fuel line, got back to his house and also ran it in a bucket for a long time. Never had any problems with it after that.

I was hesitant to raise the motor any more after reading the above linked thread but decided to add a 1/2" spacer. The Cav plate is right with the bottom now. If this is too high will I be able to hear it sucking air?

I also found out I had a 12 pitch prop. Ordered an 11 and 10 pitch just in case. I'll mark the current prop/hub and test it out to see if it is indeed spinning. Also will check the RPMs. We'll be up in Maine all next week so plenty of time to do so.

There's a 1993 25hp Evinrude with electric start and remote controls available locally for $500. If it's still there after vacation I will go look.