1984 Evinrude 7.5 hp questions.

[oregonboatnewb]

Hey guys, brand new to the forums, and boating in general... just picked up a 1984 7.5 hp 2stroke evinrude with a 12 ft fiberglass boat... I'm wondering a few things...

A) What have you guys (anyone with anything like this kind of motor) Found to be the best mixture.

B) How fast can i expect a 7.5 hp motor from the 80's to go on a 12 ft boat ?

C) Is it bad to run the motor for extended periods of time ? How long would it be alright to run it full out for, before giving it a rest ?

D) Where if anywhere could i find replacement parts, like the choke switch whcih is 1/2 broke off, or the tilt switch on the bottom of motor is cracked alittle.

Thanks !

 

[lyncraft_mechanic]

Re: 1984 Evinrude 7.5 hp questions.

Hi and welcome to the forum; before really running your motor you should do some preventative maintinence such as replace the water impellor and inspect the water pump to prevent any possiblity of overheating the motor. it is recommended to replace the impellor at least every 2 two years or every season it you run the motor in water with alot of silt and sand. I would recommend mixing your fuel 50:1, replacing the lower unit fluid, at least annually to ensure proper operation and that there is no water present in the oil. I would estimate your speed to be around 5 to 10mph. here is a good website to order parts from http://www.shop.evinrude.com

 

[jbjennings]

Re: 1984 Evinrude 7.5 hp questions.

Just curious----what kind of fiberglass boat? If it's a really light boat, then the 7.5hp should make you go about 15 mph I believe, with one person. If it's heavy, then a lot slower. The amount of weight you carry will really slow it down badly with a 7.5.
laingsoutboards.com sells used parts and new parts and I enjoy doing business with them. Iboats sells new parts for your motor, too.

If your motor is planing your boat and not loading it up too bad (i.e. going at least 12-15mph) then you should be able to run it all day if you had that much gas without stopping and it shouldn't hurt it at all if everything is working properly. That's what it's made for. If it's on a heavy boat and putting a lot of load on the motor, you need a bigger motor. Pushing a heavy load constantly at wide open isn't good for it at all.
It certainly doesn't need a "rest" if it's not overloaded and running properly.
good luck,
JBJ

Just to give you an idea, and just because I like to post pics, here's a pic of my son with an older 7.5 hp evinrude (your's should be about 3 mph faster than this one) with me in the front (I weigh about 215lbs) on a light 14ft boat. It goes about 14mph.

 

[steelespike]

Re: 1984 Evinrude 7.5 hp questions.

In good condition w right prop it will run all day long.Mix is 50:1 with TCW3 rated oil.Max rated stock speed is about 17 on a light fast boat.Lightly loaded
with 2 average weight guys should plane easily.When alone you may need a tiller extension so you can sit on the middle seat.Motor trim,weight and weight distribution will be critical.

 

[oregonboatnewb]

Re: 1984 Evinrude 7.5 hp questions.

Thanks everyone for your input... I'm going to look into getting a new impeller before taking it out... but before i even got that far, i ran into a small problem... The boat is a 1968 Ultra Lite XII Fiberglass boat (so it says on it) And the previous owner hadn't used it in years, it had a floor that he had put on over the existing sub Floor... I decided to take up the floor he built, and this is what i found...

Now Awesome ! But what you gonna do ! I called the old man i got the boat from, and he said he would pay for 1/2 the cost of supplys to get it fixed (doing labor myself, never having had a boat before, but good with a saw)
We started off simple... clearing out the dead wood seats

and removing what we could of the dry rot

Today i took some shots of the outside, and filled it to make sure it didnt have any underbody leaks.

I found 2 very small leaks, that would drip 1 drip about ever 20-60 sec even when the boat had 6in of water in it... i know the pressure will be more, when the river/lake is pressing up on the boat, so i would like to get them fixed.

 

[oregonboatnewb]

Re: 1984 Evinrude 7.5 hp questions.

Last night we Also got some supply's to repair the floor... I' didnt wanna spend the 250.00 i was quoted at a few different marina's just for the special woods/paints/calks... cause tahts worth almost as much as the boat... So i went to home depot, got 3/4in presure treated ply wood, presure treated 2x10 for the new bench's, and some outdoor no skid sand paint... I also got some calking, and some extra rubber cement that i plan on putting around the entire floor before i paint it...

Few Shots of the motor.

The Choke Switch is broke, and also in the last pic, bottom left there is a switch to raise/lower motor, and its cracked off...

Anyway, back to some questions !

What is a good/inexpensive way to repair the small leaks i have on the underside of the hull ?

The plan of cutting out 3/4 presure treated board, then calking, then roof cementing around it, then painting it twice... Think that will work ? Not looking for a lifetime fix, but just want to get it usable, for less then the boat is worth...

I took out as much of the dry rot as i could find... it would seem the rest of the boat (area's of floor i didnt remove) are almost all fiber, and seem fine, so i figure i'll just put the floor over the rest, and make sure the water can get to the back, and i can just drain the boat when i get back w/tilting trailer up.

Also, i've never had a boat motor before, so i have no idea where to check the water pump, or what an impeller is lol, please advise =)

 

[oregonboatnewb]

Re: 1984 Evinrude 7.5 hp questions.

Here are some more shots of the Engine. It just got fresh plugs, and fresh black thing that the throttle cable goes through... previous owner had just taken it to a local marina and they looked over the motor/boat, and fixed a few things on the motor before saying its ready to be sold.

Also, with a 12 ft boat, whats the largest motor i could put on it ? The previous owner had built an extra strong rear of the boat (Place the motor clips onto)

Also, From the picture of the trailer, how large of a boat do you think it would support ? the tires are 4.8 x 8, just replaced em, and rewired the whole thing... (Man i'm a boat nub)

 

[oregonboatnewb]

Re: 1984 Evinrude 7.5 hp questions.

Also, How far could i go on 5-6 gallons of gas, with a 7.5 hp motor, with 2-3 adults in the boat ? going around full speed the whole time.

 

[jbjennings]

Re: 1984 Evinrude 7.5 hp questions.

Here's my opinion, so take it for what it's worth:

1. I would forget the boat and buy a cheap, light 14foot aluminum boat to put your 7.5 on. It will run really nice on a cheapo 14foot aluminum boat. That fiberglass boat will weigh a ton with all that 3/4 plywood and the boat might not even plane.
They do have little fiberglass kits for about 15 bucks at any marina or walmart to fix your holes. The stringers look rotten on that boat. To fix a fiberglass boat where it's decent, you need to really know what you're doing and it's not really cheap even if you do it yourself since materials are kind of high. Once again---just my opinion.:redface:

2. Your trailer looks really nice and should easily support as big of a boat as you will ever need to put a 7.5hp motor on. (Probably carry 800lbs. with no problem.

3. Your motor looks nice but has one important area that I would be highly suspicious of. It's the cylinder head which has rusty bolts and discoloration which is a sign it's been overheated. Other than that, the motor looks nice. I would just get a cheapo $20 compression gauge at the auto parts stores or borrow one and see what it is before I invested further dough on it. If the compression is good, that's probably a nice motor. I would expect compression to be even or very close to even on both cylinders and above 85psi., hopefully higher.

Also, I can't believe a marina checked it out and gave the "ok" for it to sell without fixing the broken choke knob (cheap fix) and tilt lever. I would think they would freak when they saw the boat.

As far as the water pump impeller, you have to drop the lower unit and replace the water pump impeller and maybe the water pump housing. the lower unit will not drop if you don't disconnect the shift shaft even if the lower unit bolts are all out. You need to go to the library or buy a manual if you're unfamiliar with that stuff. It's easy if you have a manual to go by.
You may also need to clean the carburetor which is also not hard---nothing like a car---VERY simple. Also the manual will show you how to do this.
Hopefully you have good spark or you'll have to troubleshoot it.
Good luck either way,
JBJ

 

[oregonboatnewb]

Re: 1984 Evinrude 7.5 hp questions.

few things...

A) Thank you for your reply...

B) I'm totally F'ed lol, i already registered the boat, the day before i found all the rot. ( I wonder if they would let me change boat registration)

C) the motor starts, and seems to run just fine, we ran it at his house, only 50 deg outside, started up in about 4 pulls... once warm, idled just fine... So i'll have to go find a compression gauge (dont know how to work it) and check out the cylinders.

D) I haven't cut the wood yet, so i could return that, however i had some paint mixed, so i'm out 35 on that.

E) For fixing the fiberglass, which looks splintered and black/moldy, i found a local guy who was gonna sell me the supply's for only 40 bucks, 1qt resin 1/2 gal marine paint, MAT/ROVING/NYTEX, and free catalyst... Do you think

With registration/supply's im into the boat around 300 + the 450 i paid for the boat package(trailer/motor), which i think would be fine, if the boat planed, and didnt sink =)

What is the weight difference between a 12ft fiber vs 12 alminum... or a 12 ft aluminum vs 14 ft alminum... Cause i want something light, i'm towin beind a bimmer LOL

 

[iwombat]

Re: 1984 Evinrude 7.5 hp questions.

You should probably split this post into to parts.

1) Evinrude outboard questions which should remain here.

2) Boat restoration questions which should go in the boat restoration forum here on iboats.

 

[jbjennings]

Re: 1984 Evinrude 7.5 hp questions.

I wouldn't worry that much about the compression if it's idling fine. Sounds like you have a good motor if it will hold gear (won't jump out because of a chipped or worn clutch dog).
About the boat---I suspect after the plywood fix and all, your fiberglass boat will weigh twice that of a 14 foot aluminum boat. I would NOT go with a 12 foot aluminum boat for your 7.5hp. I'm telling you from a lot of experience that the 12 foot will be heavy in the rear with just one person and the 7.5 probably will not plane it correctly and it will be slow as your grandmother. If you get a 14 footer, the weight will be more easily distributed and it will jump on plane easier and run smoother. Plus, there's a LOT more room in a 14 footer. I know it's just 2 feet but it will seem like a lot more. With all you've invested with the fiberglass, I'd be tempted to try to use it, too. But if you fix it, keep it covered or water will get under the deck and a 100 hp motor won't push it with all that water in it.
Have you ever worked with fiberglass? I have, and I HATE it. Hate is actually too good a word for what I think about fiberglass work. And mine didn't turn out like I wanted after about 6 months (it delaminated in a couple of small places). It was my fault, but I'm just saying it's time consuming and messy and you need a little experience to get it right. I don't know as I would just count my losses on the boat but before you listen to my goofy advise you should ask some questions of someone who really knows fiberglass on the boat restoration forum and see what they think. Myself, just the weight of the fiberglass is enough to forget it when you consider your horsepower. Light = aluminum!!!
By the way, I'm very biased against USED fiberglass boats, so keep that in mind as well. Fiberglass doesn't hold up like aluminum!!!!!!
Just some thoughts,
JBJ​

 

[oregonboatnewb]

Re: 1984 Evinrude 7.5 hp questions.

JBJ,
Thanks again !!! Good news, thanks to the ineffective workers at Joes, 3 days later my registration is still in the store !!! So i can get a refund for 80 bucks on that... Also i haven't cut any of the wood, so i can return all that. Only thing i'm taking a hit on, is the blue paint i purchased that i had none slip sand mixed into it... I got a guy coming over that restores fiberglass boats later today, and i'm going to have him take a look at it, if he thinks its not worth the trouble, its gone ! I'm also gonna go get a compression gauge now and check the cylinders just to be safe... But even if i dump this boat for 100 bucks, i'm still gonna have a real nice trailer and real nice motor, for less then 400 bucks =) Might as well look at the bright, side of your life !

I'll let you know... But now i'm thinking... 14 ft boat, mabey 9.9 hp motor... or mabey 15hp, or mabey 500hp !!! Oh the possibilities

 

[oregonboatnewb]

Re: 1984 Evinrude 7.5 hp questions.

Just got back from the marine shop... they did an inspection, said motor looks pretty good, recommended changing the water pump (as they told me they would with any old motor, that didn't know all its history) A little water in the bottom area, but easy fix just swap out the gear fluids he said...


Boat i dont know what ima do... i might just fix it cheap, and put around a local river thats no wake, get a 13-15ft for lakes and such for summer time.

 

[coolguy147]

Re: 1984 Evinrude 7.5 hp questions.

wow 17 mph on on a 14ft alumium with a 7.5 hp!! man i cant wait till i get my 12ft alumium boat rated to 15hp and im gonna put a 10hp on it and man i wanna see that thing fly.


7.5 with 6 gallon will get about 6-7 hours of running time at wide open.

lol lookts better then my 1959 im restoring it also almosted finished just ahve to adjust my needles again... maybe a carb clean to and a decarb to help with my idle problems.


hey i suggest a decarb with some seafoam. ask tashadady for the instructions

 

[oregonboatnewb]

Re: 1984 Evinrude 7.5 hp questions.

The marine shop said with small motor (especialy 2 stroke) compression is really only a pass/fail test... if it idles, then a compression test isn't going to tell you anything... same with leak down, due to the small size of the engin... so i just had em inspect it, changed the plugs, and they said it looks just fine.

 

[Sandhammaren05]

Re: 1984 Evinrude 7.5 hp questions.

Good acceleration requires good compression.

2-stroke mechanic

The marine shop said with small motor (especialy 2 stroke) compression is really only a pass/fail test... if it idles, then a compression test isn't going to tell you anything... same with leak down, due to the small size of the engin... so i just had em inspect it, changed the plugs, and they said it looks just fine.