150 2 stroke on 191?

[herewego]

First post, just joined and hope to rely on you all going forward.

Picked up a 1971 191 Osprey and looking at a Johnson 150 carb 2 stroke for it. It's 370 lbs according to spec sheet.
I know the orig boat was rated for 125 hp, I believe.

My boat has a new transom raised to 25", a pair of knee braces added between the transom and stringers, and the deck has been raised what looks to be about 1.5 inches or so.

The fuel tank is approx 35 gallons and is now under deck in the the belly about midship. The leaning post is about 4 feet forward of the transom and has a bait well built in, which looks like about 20 gallons to the overflow.
I'm thinking of using a 4" manual jack plate just so I can mess around with the motor height.

The boat has a new deck of 3/4 ply, stringers rebuilt using foam. Everything is solid.

[boatnamesue]

Sounds like a nice rig.  150hp on the 191...no biggie.  In the era when your hull was built, outboards were far heavier than they are now, hence the original max hp capacity of 125hp.  The 191 has a dry hull weight around 1300lbs.  In my opinion, I wouldn't hang any less hp engine.  Though I'd seriously reconsider getting a manual jackplate.  The ones I'm familiar with require you to manually lift engine in order to raise/lower jack plate to pre-set holes.  I recon you don't want to manually raise/lower a 400lb engine.  Spend more money on a hydro jack plate so you can actually use it's benefits while underway.

[herewego]

Actually I have a car lift to lift the motor. Already have the jack plate on the boat, so thought having some adjustment might be good as opposed to bolting right to the transom. As "manual" as it is, it seems a better solution for experimenting than bolting the motor directly to the transom.

[boatnamesue]

Actually I have a car lift to lift the motor. Already have the jack plate on the boat, so thought having some adjustment might be good as opposed to bolting right to the transom. As "manual" as it is, it seems a better solution for experimenting than bolting the motor directly to the transom.

Bolting motor to transom and lifting engine...bolting jack plate to transom and lifting engine...same difference.  I believe johnson bracket allows for 4 different height adjustments in 3/4" increments, the bottom holes are slide, so you'd only need to remove the top 2 thru bolts to move engine up and down.  But since the jack plate is already on, makes sense to stick with it.

[mshugg]

. . . In the era when your hull was built, outboards were far heavier than they are now. . .

This is not exactly true.  The switch to four stroke or direct injection added weight.  The original 150 Mercury Black Max that I pulled from my 1979 CCP had a published weight of 385 lbs.  I’m not sure if that weight included the remote trim & tilt pump or not.

Here are the current lightest published weights for new 150 outboards (ranked lightest to heaviest):

Evenrude Etec 418 lbs
Mercury 455 lbs
Yamaha 478 lbs
Evenrude G2 496 lbs
Suzuki 511 lbs

These numbers are just a starting point for comparisons because some mfgs publish dry weight, some publish weight with oil, and there are differences in displacement that are a factor too.

Please note, I’m not disputing your original premise that the boat can handle the 150, just that motors are getting lighter.  In any case since the OP is hanging his older 370 lb two stroke, this part of the discussion doesn’t really apply to him.

Sorry I’m not trying to be argumentative, but many of us put a lot of thought into repowering with four strokes and the additional 100 pounds this entails.  For me, I’m going with a flotation bracket,relocating two batteries to my console, moving the CG of my fuel tank 8” forward and raising my floor, all to maintain trim and keep my scuppers above water.

[herewego]

Along these lines, is there a calc or formula for setback? Does setting a motor back 4 or 5 inches on a jack plate, for example, add effective weight at the transom that should be taken into consideration?

[mshugg]

There is formula over on Classic Seacraft.  I’ll see if I can find it later. 

[mshugg]

Here’s a link to the the process for calculating CG shifts from Classic Seacraft:

http://www.classicseacraft.com/community/attachment.php?attachmentid=13400&d=1474774043

Here’s the full discussion in case you find other useful information: 

http://www.classicseacraft.com/community/showthread.php?t=28289&page=3

Have fun!

[boatnamesue]

. . . In the era when your hull was built, outboards were far heavier than they are now. . .

This is not exactly true.  The switch to four stroke or direct injection added weight.  The original 150 Mercury Black Max that I pulled from my 1979 CCP had a published weight of 385 lbs.  I’m not sure if that weight included the remote trim & tilt pump or not.

Here are the current lightest published weights for new 150 outboards (ranked lightest to heaviest):

Evenrude Etec 418 lbs
Mercury 455 lbs
Yamaha 478 lbs
Evenrude G2 496 lbs
Suzuki 511 lbs

These numbers are just a starting point for comparisons because some mfgs publish dry weight, some publish weight with oil, and there are differences in displacement that are a factor too.

Please note, I’m not disputing your original premise that the boat can handle the 150, just that motors are getting lighter.  In any case since the OP is hanging his older 370 lb two stroke, this part of the discussion doesn’t really apply to him.

Sorry I’m not trying to be argumentative, but many of us put a lot of thought into repowering with four strokes and the additional 100 pounds this entails.  For me, I’m going with a flotation bracket,relocating two batteries to my console, moving the CG of my fuel tank 8” forward and raising my floor, all to maintain trim and keep my scuppers above water.

Agreed.  The mistake in my reply to the OP was I skipped over his hanging a 2 stroke.  I thought he was referring to weight difference between 2 strokes and 4 strokes.

[herewego]

thanks. Only reason I asked is elsewhere in the forum there are arguments that most people are overpowering and adding to much weight to the older hulls, and that they should be powered by no more than the original factory rating, or even less. As we get closer to to a 4 stroke world only, not sure how we can stay anywhere near the power to weight ratio of the old 2 strokes, but...

[mshugg]

Truthfully, if you were shopping for new power, I think you’d do just fine with a 115 which weighs about 350.  The specs on your 191 in terms of weight and fuel are really close to the 170 which performs just great with 90-115 hp.

It’s also worth checking with your insurance company.  I’ve heard, though never experienced, that they have problems insuring if you exceed capacity plate HP.

I think your question was along the lines of will I be ok, and I think the consensus is probably yes, especially since you’ve got the motor and it’s a light 150.    A lot of folks loved the carbureted 2 strokes.  I had an OMC 200 and OMC 225.  They were solid and performed well, but the fuel economy and reliability are light years ahead on the new 4 strokes and direct injected two strokes.

[boatnamesue]

Truthfully, if you were shopping for new power, I think you’d do just fine with a 115 which weighs about 350.  The specs on your 191 in terms of weight and fuel are really close to the 170 which performs just great with 90-115 hp.

Agree with shugg here ^^^.   I have the 170 with 2 stroke 115hp. Performance is superb. Your 191 is only 200lbs more hull dry weight.  So i recon your 150hp 2 stroke of similar weight will be sweet.