85-140hp out of the same block? How?

waterinthefuel · Jan 1, 2004

How do they do it? Who would want an engine that weighs as much as an 140 that puts out only 85hp? I don't own either engine, I've just always been curious.

wilde1j · Jan 1, 2004

Re: 85-140hp out of the same block? How?

This is typical in the marine industry. One basic powerhead for a number of HP's. The differences are in induction, timing, porting, etc. There's no other way so many different HP's could be offered given the volume in each size.

ledgefinder · Jan 1, 2004

Re: 85-140hp out of the same block? How?

There isn't as much difference as you might expect between the 85 and 140. The 85 is tuned for low & mid-range power, and will "feel" stronger than a 140 in that range. For example, it'll pop a skier up easier. The 140 needs to get wound up before it can pull hard. Further, the 140 burns out easier. Properly-tuned & propped, 140s can be run full-throttle 24x7. But clog up a carb jet so a cylinder runs lean, and it's more prone to overheating than an 85 would be. OMC also made 150 to 235hp from a 150 cubic inch V6, and 55 to 75hp triples from a 50 cubic inch triple. Swapping a 85hp V4 onto a boat that had the 75hp triple, the first thing you'll notice is that the 85hp feels a ton stronger - accelerates like you've downshifted a gear in your car. The second thing you'll notice is your gas gauge now drops like a stone...

Melvin Hatcher · Jan 1, 2004

Re: 85-140hp out of the same block? How?

ledgefinder Are you saying that the 85 have more low end torque, mid range giddy up and go than the 140 and uses more gas than the higher horsepower 140? Then what should one expect from the 140, only top end speed? The reason behind my question is; I have a XP 150 and I would like to know how to bring it up to 175, 200 or more horsepower.

Dhadley · Jan 1, 2004

Re: 85-140hp out of the same block? How?

Some of the 150 XP/GT's did indeed use the 200 port timing. And the XP/GT heads are an excellent design. Good luck!

Melvin Hatcher · Jan 1, 2004

Re: 85-140hp out of the same block? How?

Is there a way that one can check the port timing and know the horse power rating of a powerhead?

Dhadley · Jan 2, 2004

Re: 85-140hp out of the same block? How?

The port timing is the distance from the top of the port opening to the deck surface. If the deck has been cut you will get a different measurement so you will have to determine the deck height first. Deck height is the distance from the crank centerline to the deck surface. Port area is the overall open area of a given port. Ports that have been "squared" are capable of flowing more fuel in theory. You can also lower the bottom of the port opening to gain area without affecting port timing. On certian blocks you can "scallop" the block and pistons to allow more possible flow too. Port shape has a lot to do with how the fuel is scavenged. There are oval ports, square ports, T ports, V ports, Z ports and so on. Each horsepower has very specific stock port measurements but the factories do not publish them. Its pretty easy to compile your own measurements from other blocks and/or sleeves. Race sacnctioning bodies such as APBA sometimes publish specific specs for certian stock classes. Good luck!

waterinthefuel · Jan 4, 2004

Re: 85-140hp out of the same block? How?

We have a 1990 150xp. I'm curious if it's possible to crank it up to 200hp and not strain anything.

Dhadley · Jan 4, 2004

Re: 85-140hp out of the same block? How?

Sure. In fact some of those had the 200 port timing already. All were pretty close. And the XP/GT heads are very very good as produced. We've seen folks do this many times only to be disappointed because their hull did not respond to small torque increases or the set up was not maximized to start with. Make sure you are taking full advantage of what you have now. BTW -- you will never be able to create the torque of a 200 looper with a crossflow. Just something to keep in mind. Good luck!

Melvin Hatcher · Jan 5, 2004

Re: 85-140hp out of the same block? How?

Okaaaaaaaaaaaaaaaaaaaaaaaaaaaay Dhadley, I hear ya. Some of the GT/XP have the port timing of the 200's and some do not. Now, how do I know if my 1985 XP 150 does or does not have the 200 port timing? How do I modify my engine to make sure it has the 200 timing or produce 200 hp, or better, who holds the secrets? I can buy book on how to hot-rod a Chevy engine, but I can not find anything on how to hot-rod a boat motor.

Dhadley · Jan 5, 2004

Re: 85-140hp out of the same block? How?

Tell us more about your rig and how its set up now. If you have a 22' Aquasport and its set up at 5800 with an average load I doubt you'll see much improvement. If you have a 18' Hydrostream and its only turning 5000 you can gain a bunch from fine tuning the set up. I wouldnt get into internal mods until youre sure of two things; 1- Your set up is maxed out now and 2- Your hull will respond to small increases in torque. Let us know!

Melvin Hatcher · Jan 5, 2004

Re: 85-140hp out of the same block? How?

Dhadley, I don't want to hog or take over waterinthefuel's orginal post. Should I post another message on how to get more power from a XP 150 cross-flow?

Dhadley · Jan 5, 2004

Re: 85-140hp out of the same block? How?

Since he has a 1990 150XP and the background has been laid, I'm thinking he wont mid sticking with this thread. Its his thread so its up to him. Personally I think if we started over some of the data already posted may get lost or if someone joins in it may be confusing. Lets see what waterinthefuel thinks. Good point!

waterinthefuel · Jan 5, 2004

Re: 85-140hp out of the same block? How?

Hey guys that's fine. If you want to create another thread you can, but using my post is perfectly alright with me. Heck, I asked the question which changed the topic anyway!

Dhadley · Jan 5, 2004

Re: 85-140hp out of the same block? How?

Sounds good! I still think the topic is very related as many folks have the same question. Many times when we had the marina people up graded from a 115 to a 140 (or a 175 to a 200) and were disapointed with the results. You have to remember that in like designs you may still have the same bore and stroke, gear ratio, prop diameter and same target rpm. However when going from a crossflow 200 or 235 to a 200 looper, the results are most often dramatic because of the increased torque. I have seen cases where the rig was not set up to the max and simply changing the set up made a "night and day" difference. Thats why we need to see where were at before we can plan a trip to go where we want to be. Its like asking how to get to my house. I cant tell you until I know where you are.

waterinthefuel · Jan 5, 2004

Re: 85-140hp out of the same block? How?

I think I know what you mean. How can it be more horsepower if it's the same engine swinging the same prop at the same RPM?

Melvin Hatcher · Jan 5, 2004

Re: 85-140hp out of the same block? How?

Thanks waterinthefuel Dhadley, My boat is a 2003 19'2 Key West CC. I think the weight is 1500 lbs. The motor is a 1985 Evinrude XP 150, prop is 14 1/4 X 21+, top speed GPS 48.5, Speedometer 50 RPM's 4900

Dhadley · Jan 6, 2004

Re: 85-140hp out of the same block? How?

OK. At 4900 you arent taking advantage of whats available. Even if you spent hours and hours and hundreds of dollars adding more HP, you cant take advantage of it until you get in the "power curve". First lets verify that the tach is accurate. What brand is it? Is it set on position 6? Once the tach is verified, your target rpms should be 5900 with an average load. A 21" prop is a bit more than we normally run on that boat but you may have a light average load. What brand prop? We are assuming (since you mention 21+) that its a SSTII 3 blade. We normally end up raising the motor and running a 19" Turbo 3 blade or if there is a jack plate, a 4 blade 20" Turbo. Traditionaly those boats are rigged with the motor fairly low. Try raising the motor and see what happens. Dont worry if the prop slips coming on plane or in a tight fast turn. Especially if its worn at all. Right now we are only interested in top rpm vs top speed with a change in X dimension. Use the same prop. Make one change at a time. Watch and record the water pressure. Let us know! Good luck!

Melvin Hatcher · Jan 6, 2004

Re: 85-140hp out of the same block? How?

I understand that I need to get the R's up around 5850 - 5900 to get the engine in its best power curve. However, the prop I am using is a SST II OMC used on my old boat. I will re-prop, or re-pitch the old prop as soon as I get the engine running in tiptop shape. Right now, I am suffering from a lean carb condition. Today I bought carburetor kits to overhaul the carb during the winter. The weather is cold here in Maryland, so I will not be during much work on the boat for the next few months. I have fogged the engine, changed the lower unit oil, and put stabilizer in the gas. In addition, on the warmer days here in Maryland I will verify the tach and check/replace the regulator/rectifier, which I think is bad. Before getting into engine mods or the how's to get 200 hp out of a 150 I would like to know the correct height to set the motor. The plate above the prop on the lower unit is even with the vee bottom of the boat.

Dhadley · Jan 7, 2004

Re: 85-140hp out of the same block? How?

Dont let enthusiasm change your testing sequence. First you need a baseline. I didnt realize your motor wasnt running right so the baseline you have now is not valid. If the carbs are suspect go ahead and clean them as you planned. Do not change the X dimension (engine height) or replace/change/repitch your prop. Once the carbs are done and you are ready to test in the spring see what the rpms come to then. That will establish the true baseline with the motor running at 100%. As far as the engine height, there is no absolute dimension for every rig. It depends on your load distribution, hull design, lower unit design, set back and largely on the prop configuration. A Raker will run higher than your SSTII. A Stiletto will run higher. A Turbo will run higher yet. A good 4 blade will run even higher. Take your time. Get the carbs done and test when you can. Make sure the carbs are what was the cause of your motor not running correctly. While your doing the carbs, check spark and take compression.

85-140hp out of the same block? How?

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