Are my wot rpms too high ?

[jimmbo]

The 90hp crossflow makes its peak horsepower at about 4700 - 4800 rpm. At 5500 it will be making less than 90hp and the power drops off very rapidly above that. It simply is not ported to breath deeply at higher rpms. If you want a 99 crossflow to make peak power at higher rpms, you need the porting of the 110/112/115/135/140 block and carbs. To make the most stock power, the exhaust needs modification and different heads. After that it is specialty shop work and the engine can spin much faster, but it will be WORK to drive it and will have no low speed power and be suitable for racing hulls only

 

[StingRay_90V4]

The 90hp crossflow makes its peak horsepower at about 4700 - 4800 rpm. At 5500 it will be making less than 90hp and the power drops off very rapidly above that. It simply is not ported to breath deeply at higher rpms. If you want a 99 crossflow to make peak power at higher rpms, you need the porting of the 110/112/115/135/140 block and carbs. To make the most stock power, the exhaust needs modification and different heads. After that it is specialty shop work and the engine can spin much faster, but it will be WORK to drive it and will have no low speed power and be suitable for racing hulls only

Honestly. I'm not at all interested in anymore speed . After freeing up the timer base. The boat works really well. Tons of hole shot for when we go tubing or skiing. And at 44mph and 45 mph ( Seems to be day and weather dependant which one of the two it will hit. ) I gained 4 to 5 mph on my top speed from last summer and when we first bought the boat 4 years ago. Last weekend with five people in the boat. I was still pulling off 42mph. That's a mile or two faster then it was last year with just myslef in the boat. I don't think my boat will ever be as fast as yours in that video. That was just crazy fast. Even interalian's is a bit more work then I may ever want to get into. But we will see someday maybe. If I rebuilt it ever. Our we may just buy an etec 115 h.o or a 135 etec h.o and a new boat someday. Will see. As I have said. Everyone says something different about these motors. Some say run them to 6000rpm or even higher. Some say 5500. Some say 5800 rpm. Idk .. Obviously if some people are running 60mph and above they must be running some high rpms too.

 

[jimmbo]

I can say they are not designed to live long at speeds higher than the recommended RPM range, but... A person can run an engine any which way they want to.
interalian did a very thorough and fine overhaul/rebuild of his power head and did it right. and didn't cheap out. It shows by the way his engine runs

 

[ondarvr]

If you were running it at 5,800 all the time, and what you wanted was the highest speed possible, you may benefit from a little more pitch. But you said you weren't that concerned about top speed and liked the hole shot and pulling toys better option, this is what you have now. If you don't run it much, or at all at 5,800, there will be no possibility of excess wear or stress.

 

[interalian]

Ha! You call that a hole-shot? ...

Bone stock '83 140. 13 3/4 x 23 SRX. 62.9 mph.

Problem turned out to be a split in the hose from thermostat cover to heads. Didn't leak at idle but at higher revs it peed up all over under the motor cover.

www.youtube.com/watch?v=Lqat6iRbpRo

Please ignore my obnoxious buddy JR ...

Bet you're running a better hull than me. My tin tub is about 1550lb with fuel and fattie (yours truly). None of my clips show me 'dropping the hammer' so much as 'rolling on' too.

And I'm running at 3300' elevation. One of these days I'll get it back on the chuck and see what an extra 15% power and denser water will do. With the 90, we'd run 44-45 on the salt, never over 41 up here. The old readings were just with the optimistic speedo. I saw 48-49 on GPS last year. At 3300'.

And your buddy is a hoot.

 

[interalian]

I'd like to keep mine under 5800 - don't want it to wear too quick. But maybe I'll go with a 17" stainless if that'll work better.

 

[V153]

Routinely ran this one 63 6400. '85 90hp. 020 wiseco pistons. Otherwise stock. Top hole on a Glastron V153. 54.8 mph was my best run.

I ran that boat, hard, virtually every Sunday from 2007 thru 2011. Motor failed due to corrosion. Cylinder wall rotted away and lost compression on #3. Despite religious flushing. So I pulled it apart and built something else.

I still have those pistons. They look like new. Good oil and good gas my friends. Revvin em up a lil once in awhile ain't gonna hurt em.

 

[V153]

I'd like to keep mine under 5800 - don't want it to wear too quick. But maybe I'll go with a 17" stainless if that'll work better.

Yeah definitely try a ss prop. I'd recommend a Raker.

 

[V153]

Here's an oldie: Ride along. Camera boat is my lil bro's 19' Stingray w/4.3 I/O.

www.youtube.com/watch?v=30rnsLF_IR8

 

[V153]

The 90hp crossflow makes its peak horsepower at about 4700 - 4800 rpm. At 5500 it will be making less than 90hp and the power drops off very rapidly above that. It simply is not ported to breath deeply at higher rpms. If you want a 99 crossflow to make peak power at higher rpms, you need the porting of the 110/112/115/135/140 block and carbs. To make the most stock power, the exhaust needs modification and different heads. After that it is specialty shop work and the engine can spin much faster, but it will be WORK to drive it and will have no low speed power and be suitable for racing hulls only

Nonsense. Rpm = hp with an old 2 stroke. After '78 or so porting is the same.

 

[V153]

Here's my "88 extra special" still making hp @ 6200: (Just watch the first ten seconds.)

www.youtube.com/watch?v=gwnHfbCHx-I

 

[jimmbo]

Nonsense. Rpm = hp with an old 2 stroke. After '78 or so porting is the same.

Torque x RPM equals HP. The porting is different between the 90 and the 110/112/115/140. There are other differences too. But since your mind is made up, why confuse it with facts.

 

[StingRay_90V4]

I have to ask now out of curiosity . What is the difference between say my 90 and a 115. Other then the carbs ?

 

[interalian]

I have to ask now out of curiosity . What is the difference between say my 90 and a 115. Other then the carbs ?

Porting, as in the size and location of the intake ports. The 140's ports looked to be nearly twice the size of those in the 90. Some say the 90 didn't have the intake filler rubber plugs, but my '82 90 did. The fillers reduce crankcase volume to aid in performance (increased crankcase compression).

 

[jimmbo]

I have to ask now out of curiosity . What is the difference between say my 90 and a 115. Other then the carbs ?

Also depending on the year of the 115. Pre 1985 had a flat back exhaust cover, while the post 1984 models had the bubble/turtle back exhaust, which created a different exhaust tuning. Also the exhaust tube/megaphone Heads were also different,
A 90 can be converted into a 115/140. Some machining and parts are what is needed.

 

[interalian]

Also depending on the year of the 115. Pre 1985 had a flat back exhaust cover, while the post 1984 models had the bubble/turtle back exhaust, which created a different exhaust tuning. Also the exhaust tube/megaphone Heads were also different,
A 90 can be converted into a 115/140. Some machining and parts are what is needed.

I was persuaded not to do machining on my build, rather use the 140 block. My choice was easier as my 90 was saltee and the 140 was a lake boat from Saskabush.

 

[jimmbo]

Mine did bunny hops too 1998 GS180 98 150 Fucht

 

[jimmbo]

I was persuaded not to do machining on my build, rather use the 140 block. My choice was easier as my 90 was saltee and the 140 was a lake boat from Saskabush.

I remember when you deciding that, and where to get the block bored

 

[StingRay_90V4]

When and if i rebuild it in the futire of it ever needs to be before wi get a newer boat . if rebuilt I would love to slap on the carbs from a 115 and some of the porting needed and just use my 90 Lu and exhaust. Even if I could increase the hp that way from 90 to say 100. I would be more then happy. It is a light boat at only 865lbs. I have been watching a lot of boating reviews. New boats are so heavy and slow for there hp. I mean like 115hp and 130hp only doing 38 to 40 mph ?

 

[interalian]

The '82 90hp LU and its exhaust showed all the same part numbers as the '79 140 I used as a donor. I've read that '77s had a better tuned exhaust megaphone. I spent a lot of hours going over part numbers on the BRP parts site before I decided what I was doing. It made a lot of sense for me to use my original LU since I knew it was in top shape. Good thing too, as when I removed the powerhead from the 140, I found a bunch of problems including a totally ruined upper motor mount (NLA).