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I am thinking about installing a 4 inch jack plate on my 1989 18' Outrage with a 150 Suzuki.

Has anyone done this and if so, would it make it porpoise more. I have batteries mounted in console.

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Our 19 Outrage II (same hull as yours, with different interior) is equipped with a 150 HP 2-Stroke Yamaha (approx. 430 lbs), mounted on a 6" set-back jack plate. The boat was configured like this when I purchased it, so I can't tell you how it performs compared to prior to the set back/jack plate installation.

As configured, the boat performs very well but I notice a tendancy for the stern to squat, and as far as porposing is concerned it seems very touchy when it comes to trim. In other words, it is prone to porpoising unless the trim is adjusted just so.

These older classic-hulled Whalers are not as full in the stern sections as modern designs, which are beamier and designed to handle the weight of modern 4-stroke outboards. So these older Whaler designs from the 2-stroke era do not like a lot of weight on the stern. Placing an engine on a set-back plate where it is not supported by the buoyancy of the hull, is like adding weight to the stern due to the leverage effect. If you go that route, I would suggest no more than 4" of set-back (as you mentioned) and less would probably be better. Especially given that your 150 Suzuki is likely quite a bit heavier than my engine.

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JRP

Thank you for the information. Yes my outboard is heavy. (about 500 lbs.)

I use it offshore and bays and wanted to be able to go in fairly shallow waters.
I am hoping 4 inches won't make to much difference.

So with your engine adjusted about all the way in your porpoising is minimal?

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Adjusting the engine trim in reduces porpoising. It doesn't have to go all the way in, it just can't be trimmed out as much as one might like for optimal boat speed/engine rpm.

Yes, that is a fairly heavy engine you have. Probably 100+ lbs heavier than what they had in mind when they designed this hull back in the early-'80s. Pushing it farther aft on a set-back bracket will make it seem even heavier. Just something to keep in mind....

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I installed a 4" jack plate on my 1985 Outrage 18 with a 150 hp four stroke Suzuki. If it makes the stern sit appreciably lower, I can't tell.

It does allow me to idle back into shallower water tan I could previously.

I think it was money well spent.

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Spud

Thanks for the information. Do you go offshore and if so could you tell any difference.

I do a lot offshore but wanted to be able to go in shallow water in the bays.

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Maybe I can help out here, although I'm sure there are some here that will disagree.

Take a look at the Outrage 18 album on the Personal Website link. Ask me whatever questions you choose. I bought this boat new in 1986 and have been running jakplate installed engines on it since 1991. For reference, the jakcplates have a 10" setback, and each engine weighs 305#. Batteries are installed in the stern splashwell quarters, as Whaler specified. The boat runs and rides well, planes off fast and handles big seas well. People who have ridden in the boat say it rides better than their non-jackplated engines with a 150 set directly on the transom. Transom drains are plugged keeping the splashwell dry at rest, and a 500 gph bilge pump gets rid of any small amount of water that ever splashes in.

There is one widely misunderstood performance feature of jackcplates,and that is that you have to trim the engine out/up for max speed like you do on a transom mounted engine. A highly trimmed outboard is not the most efficient, as prop thrust is angled up, instead of pushing the boat straight ahead, and this in turn pushes down on the transom in order to raise the bow for more speed. Critical thrust is therefore being lost and wasted. A jackplate mounted engine, with engine raised optimally for minimal drag, does not need to be angled "up" for max speed. The engine should be run vertically, and the performance prop usually needed, does the additional bow or overall hull lifting. This is why jackplated boats generally have better performance.

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Very helpful information. Thanks!

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Yes as Finnigan explained, you'll also get better performance running offshore.

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have a look at my Personal Page.
I have a T-H Marine jack plate since 2005.
Please ask!

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Finnegan your 90HP Mercs only weigh 305#???? What is the complete model number as want to try to find one of those to put on my heavy Montauk 150 which is rated for max.305# outboard per the nameplate/manual.
Yes I know the HP is higher but weight is what counts. Like an airplane rated for 4 occupants (640 lbs) that would be good only for 2 of me and maybe a pre-teen kid and with myself and 2 buddies wouldn't get off the ground.
You can send me an email as I don't want to take away from this Jackplate posting.

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EJO - The engines are Mercury 3 cylinder 2-stroke 90's. Mercury manufactured this engine from 1997-2010, so finding a good used one should not be a problem. You can also buy them comletely re-manufatured. For many years, they were the standard engine for the later white classic Montauks and the 170 Montauks. They are quiet running, very powerful for the 90HP rating (I have been told about 100 actual HP), and carry their own oil tank, so no separate tank is needed to clutter up the boat. I have often thought this engine would be a perfect fit for a 150 Montauk. It would be a simple bolt up to your boat, with all rigging useable. They will outperform both the old Yamaha 2-stroke 90, or the newer Evinrude E-tec 90. They are not too bad on fuel either. My Outrage 18, with the twins and 22" Laser II props, cruises at 30 MPH and 3 MPG. I would guess a 150 with one of these would do around 46-47 MPH.