Engine exchanges on a Sport 15

A conversation among Whalers
Oldslowandugly
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Engine exchanges on a Sport 15

Postby Oldslowandugly » Sun Apr 11, 2021 8:39 pm

Is a SPORT 15 too heavy for a 30-HP engine?

BACKSTORY. My 1993 Evinrude 48SPL lower unit showed water in the oil when I drained it in 2017/ The cause was the shifter shaft seals; I repaired that myself. In 2020 I found water in the oil. This time the leaking is deep inside the gear case. My favorite shop is trying to re-sealed the gear case.

My favorite shop is having a very hard time getting a bearing out. The bad seal is under the stubborn bearing. If this takes a very long time, or I need to find another lower unit, my back-up plan is to switch over to my 1985 30-HP Evinrude.

The 1985 Evinrude 30 has a much bigger carburetor and produced more power than my 1980 Johnson 35-HP engine.

I know I can putt around with [the 1985 Evinrude 30-HP engine, but could the 40-HP get [the SPORT 15] on plane with the proper propeller?

The 1985 Evinrude 30-HP was able to plane my flat-bottomed Lund 18 foot aluminum skiff very well. I know the Sport has a superior hull design.

jimh
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Re: Engine exchanges on a Sport 15

Postby jimh » Sun Apr 11, 2021 11:37 pm

See the REFERENCE Section article on the 15-foot hull. The minimum horsepower to put the 15-foot hull on plane is given there:

http://continuouswave.com/whaler/reference/15/

The minimum horsepower recommendation (20-HP) is for a very lightly loaded boat.

I recommend you buy a new Yamaha F50. You will have a lot more fun with the SPORT 15. Use your COVAD-19 stimulus check for the down payment. Buy now before inflation and currency devaluation raise the price of imported outboard engines to even higher prices.

Oldslowandugly
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Re: Engine exchanges on a Sport 15

Postby Oldslowandugly » Mon Apr 12, 2021 5:42 pm

Thanks Jim, I forgot about that reference. So if a 20hp motor will move a 15 footer, them my husky 30 hp should work just fine. Speed is not a requirement. As for the 30 hp rating, I read somewhere that during the late 1970's/early 1980's the outboard motor manufacturers were under fire for exaggerating the horse power ratings. They had to de-rate them and Evinrude wanted to offer the "most powerful 30hp" in the industry. Thus, in 1985 what used to be a 35hp motor got a bigger carburetor and a different gear ratio in the lower unit and rated it at 30hp. It put my 35hp to shame. In fact it put my 40hp to shame. So now I am confident it will push my 15 footer well. Thanks!

biggiefl
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Re: Propeller recommendation for a Sport 15

Postby biggiefl » Thu Apr 22, 2021 11:27 am

Use a 10x13 prop. She will do around 30.
On my 24th Whaler. Currently in the stable: 86 18' Outrage, 81 13' Sport(original owner), 87 11' Sport, 69 Squall(for sale cheap).

Oldslowandugly
Posts: 511
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Location: Queens NY

Re: Engine exchanges on a Sport 15

Postby Oldslowandugly » Thu Apr 22, 2021 11:32 am

It looks like my 48hp will not be ready anytime soon. I pulled my 30hp out of the shed and inspected it. Under the powerhead cover looks as good as when I put it away. On the outside the paint suffered. I am pretty sure the control cables will interchange since both motors are post-1979. My books show the electrical engine harness wiring to be the same also. The only thing I have to verify is if the actual size of the engine connectors are the same. If they are it will be plug-and-play. If not- problems.

Oldslowandugly
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Re: Sport 15, 30-HP

Postby Oldslowandugly » Thu Apr 22, 2021 11:40 am

Biggiefl- that is the prop I have. It made my 18ft Lund Skiff fly. This 30hp has a higher gear ratio than my 35hp and it can push a bigger prop than the 35 could. I had to use a 10.5 x 11 prop on the 35. EDIT: The engine harness connectors are the same. The pin-outs are different. I found another 48hp engine harness on EBAY so when it comes I can re-wire it for the 30hp. That way I can use either motor and use the same controls and wiring that are on the boat now. I will begin to take the 48hp off and mount the 30hp. Fishing season is upon me and I can't wait for the 48hp to get fixed.

Oldslowandugly
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Re: Variation among carburetors on older OMC engines

Postby Oldslowandugly » Mon Apr 26, 2021 6:41 pm

I discovered why the 1985 30-HP engine ran so much better than the 1980 35-HP engine:the 30-HP used a slightly bigger carburetor and a #63 jet. The 35-HP used a smaller carburetor and a #59 jet.

BACKSTORY: I used to have a 1969 Johnson 40-HP engine, and it also used a single carburetor with a #63 jet.

The only difference between the 1969 and 1985 carburetors was the 1969 had an adjustable low speed needle jet and adjustable high speed needle jet.

The 1985 has a fixed low speed jet and a fixed high speed jet.

Both 1985 and 1969 used a #63 high speed jet.

The 30-HP runs around thinking it is really a 40-HP.

Oldslowandugly
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Re: Mounting the 30-HP engine; adding neutral safety switch; getting engine running, checking thermostat

Postby Oldslowandugly » Wed Apr 28, 2021 8:56 pm

The 30-HP engine is mounted. Even though I have a neutral-start-safetly switch at the remote control box, I added another to the shifter mechanism right on the motor. I had the correct switch in my spare parts. Since I have both electric and rope start on this motor, there is also a cable interlock for neutral start. Not excessive safety with grandkids running the boat.

Next step in the project is to get the 30-HP engine to run; followed by checking the thermostat is working correctly.

[A very confusing sidebar about the details of circuits and wire insulation colors in pre-1996 OMC engine harnesses has been deleted from this discussion--Moderator]

Oldslowandugly
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Re: Engine exchanges on a Sport 15

Postby Oldslowandugly » Sat May 01, 2021 6:23 pm

The 1985 Evinrude 30-HP engine is working well. It starts up and idles well. All the electrical features are functional like choke, tachometer, temperature gauge, electric start, safety lanyard engine stop switch, and battery charging.

I decided against using a larger carburetor because that particular carburetor requires a problematic primer system.

I have both the manual and electric primers in my parts stash and I dislike them both. Call me old fashioned, but I prefer a mechanical choke.

The carburetor I am using (is from the other, 35-HP engine and) has both electric and manual choke. If I find the smaller carburetor (from the 35-HP engine) is too weak for this Sport 15, then I will be forced to go with the larger (original) carburetor (from the 30-HP engine).

Now that I know the engine runs well, I drilled the two engine mounting holes in the transom, and bolted this engine in place.

Good thing I double-checked the lower unit oil. It was old and dirty.

With the rope starter, I can start the engine even with a dead battery.

Oldslowandugly
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Re: Engine exchanges on a Sport 15

Postby Oldslowandugly » Tue Jun 01, 2021 9:07 pm

The 30hp Evinrude starts, idles, and shifts well. Low speed is fine. It wants to jump up onto plane but that is where it struggles. When it finally gets up on plane it is not reaching operating rpm range. The range is 4500 to 5500 and this is just barely getting to 4800. You can feel it laboring. This prop has 13 inches of pitch. I ordered a Solas prop with 12 inches of pitch. I am glad Solas makes props in one inch pitch increments. OMC only made props in two inch increments. I once had an 11 inch pitch prop on this motor but it wanted to over-rev too easily. I am hoping the 12 inch pitch is the happy medium. It appears my 15 foot Whaler as I have it outfitted is substantially heavier than my old 18 foot aluminum skiff.

Oldslowandugly
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Re: Engine exchanges on a Sport 15

Postby Oldslowandugly » Mon Jun 07, 2021 1:10 pm

The SOLAS prop with 12" pitch made a huge difference. It scoots along on plane well with just me in the boat. Now I need to test with company aboard. Another problem surfaced. When my tach gets to 5200 rpm, it drops back down to 43-4500 rpm. Even though the boat is up on plane and accelerating. I have seen this before but at much lower rpm. The seat-of-the-pants gauge says it is running great though. I am pretty impressed that a 1985 Evinrude 30hp motor can push the Sport 15 as well as it does.

Oldslowandugly
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Re: Engine exchanges on a Sport 15

Postby Oldslowandugly » Thu Jun 10, 2021 9:52 pm

Testing reveals the addition of another passenger hurts performance a lot. That would indicate another reduction in propelor pitch. But before I do that my next task is to change carburetors. The 1985 30hp used a slightly larger carb than the 1980 35hp and with a high speed jet 4 numbers larger. Very similar to my old 1969 40hp Johnson. The 30hp air horn is 1/8" in diameter larger than the 35hp. Unfortunately the air horn is not drilled and tapped for the choke mechanism, and I am forced to use the primer system. Since the float bowls interchange, I used the 35hp bowl since it has an arm to mount the choke solenoid or primer solenoid. Once I install this carb I need to verify my total timing is correct. Then I can safely test this at WOT.

Oldslowandugly
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Re: Engine exchanges on a Sport 15

Postby Oldslowandugly » Fri Jun 11, 2021 6:28 pm

Good thing I checked the timing. I had to retard it a few degrees. I installed the modified 30hp carb and the electric primer works OK. It idles very nicely. WOT is better too. I can actually drop the rpm a bit after getting up on plane. This with just me and my pandemic pounds. I still think I will need to drop the pitch another inch to carry any more load.