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Author Topic:   21' Revenge power

H2obio posted 08-07-2013 06:51 PM ET (US)
Hi all. I'm considering re-powering my old [Boston Whaler REVENGE 21] with a 115-HP two-stroke-cycle engine or a 90-HP four-stroke-cycle enigne, but I'm concerned that it might be under powered. Thoughts? Thanks in advance, Ron
mkelly posted 08-07-2013 09:21 PM ET (US)
I have never owned the Revenge model but have a 19' Outrage with a 150. The 21' Revenge is comparable in weight but is rated for 200 HP. You'll need at least 150 to carry much load & not run the heck out of the motor....get a 200 & you can do whatever you want and be very happy.
Hoosier posted 08-07-2013 09:46 PM ET (US)
Suziki DF-175.
Tom W Clark posted 08-08-2013 09:49 AM ET (US)
I think anything more than 150 HP is a waste.
Though rated for 200 HP, the Banana 21s perform very well with half of that. 90 and 115 HP outboards are not uncommon on these hulls.
I have a brother-in-law with an Outrage 21 with a 90 HP Evinrude. Even with four big guys on board it will leap on plane. That boat tops out at 34 MPH.
With 200 HP it would well exceed 50 MPH. How fast do you need to go?
H2obio posted 08-08-2013 10:53 AM ET (US)
Thanks guys,
I'm not looking to go fast anymore, it's going to be a fishing boat, but I do want enough hp to get me out of trouble......I fish the north coast of ca and out the gate.
Thanks, Ron
jimh posted 08-09-2013 12:27 PM ET (US)
I recall a cruise one afternoon on a 21 Outrage. There were five adults and a dog aboard. The engine was an old 150-HP six-cylinder that was actually running only on five cylinders (although the skipper did not realize it at that time). There was no problem accelerating the boat to plane. That hull is easily driven.
goldstem posted 08-09-2013 07:01 PM ET (US)
we had a 21 with an old 140 evinrude crossflow (really a 115).
it would plane the boat running on 3 cylinders. I've been told that hull is quite scary with a 2000... If we still had ours we would probably do 115-150 fourstroke.
H2obio posted 08-10-2013 08:23 PM ET (US)
Thanks all, I'm looking at a 115 two stroke.
mkelly posted 08-11-2013 12:36 PM ET (US)
guys, not to call the old man card but come on, a 2,000 lb boat deserves at least a good six cylinder block. Too much stress on a smaller motor & with the gas technologies today, you will burn the same or less with the larger 4-stroke. Just my two cents but the 175 Suzuki is light, actually just a cylinder motor, & a good fit. I'm out on this one but have at it.
2manyboats posted 08-13-2013 09:22 PM ET (US)
We had / have a 21 Revenge, with the Mercury 150 2 stroke it would run just shy of 50mph. We put a 130 Honda on it and it still ran mid 40s and we regularly ran it with 6 or 7 adults on board with no problem. Properly propped a 115 will work fine.
jimh posted 08-14-2013 01:24 PM ET (US)
I do not see the two choices offered as being equivalent. Compared to a 90-HP four-stroke-cycle engine, a 115-HP two-stroke-cycle engine will have 25-HP greater power, and it will probably be able to deliver better acceleration due to the excellent low-speed torque available from a two-stroke-cycle engine. An increase of 25-HP in a 90-HP engine represents an increase in power of 28-percent, which is a significant increase. It is also seen that engines of four-stroke-cycle design must reach very close to their maximum rated engine speed to develop their rated horsepower, while two-stroke-cycle engine tends to be able to develop their rated horsepower at lower engines speeds and to deliver that horsepower over a wider range of engines speeds. The result is that the two-stroke-cycle engine tends to out-perform the four-stroke-cycle engine in an application like an outboard engine for a boat. When the two-stroke-cycle engine has 28-percent greater horsepower rating, the difference between the two engines will be even more remarkable.
silentpardner posted 08-17-2013 01:42 AM ET (US)
[Moved to a separate discussion on a new topic.]

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Author	Topic: 21' Revenge power
H2obio	posted 08-07-2013 06:51 PM ET (US) Hi all. I'm considering re-powering my old [Boston Whaler REVENGE 21] with a 115-HP two-stroke-cycle engine or a 90-HP four-stroke-cycle enigne, but I'm concerned that it might be under powered. Thoughts? Thanks in advance, Ron
mkelly	posted 08-07-2013 09:21 PM ET (US) I have never owned the Revenge model but have a 19' Outrage with a 150. The 21' Revenge is comparable in weight but is rated for 200 HP. You'll need at least 150 to carry much load & not run the heck out of the motor....get a 200 & you can do whatever you want and be very happy.
Hoosier	posted 08-07-2013 09:46 PM ET (US) Suziki DF-175.
Tom W Clark	posted 08-08-2013 09:49 AM ET (US) I think anything more than 150 HP is a waste. Though rated for 200 HP, the Banana 21s perform very well with half of that. 90 and 115 HP outboards are not uncommon on these hulls. I have a brother-in-law with an Outrage 21 with a 90 HP Evinrude. Even with four big guys on board it will leap on plane. That boat tops out at 34 MPH. With 200 HP it would well exceed 50 MPH. How fast do you need to go?
H2obio	posted 08-08-2013 10:53 AM ET (US) Thanks guys, I'm not looking to go fast anymore, it's going to be a fishing boat, but I do want enough hp to get me out of trouble......I fish the north coast of ca and out the gate. Thanks, Ron
jimh	posted 08-09-2013 12:27 PM ET (US) I recall a cruise one afternoon on a 21 Outrage. There were five adults and a dog aboard. The engine was an old 150-HP six-cylinder that was actually running only on five cylinders (although the skipper did not realize it at that time). There was no problem accelerating the boat to plane. That hull is easily driven.
goldstem	posted 08-09-2013 07:01 PM ET (US) we had a 21 with an old 140 evinrude crossflow (really a 115). it would plane the boat running on 3 cylinders. I've been told that hull is quite scary with a 2000... If we still had ours we would probably do 115-150 fourstroke.
H2obio	posted 08-10-2013 08:23 PM ET (US) Thanks all, I'm looking at a 115 two stroke.
mkelly	posted 08-11-2013 12:36 PM ET (US) guys, not to call the old man card but come on, a 2,000 lb boat deserves at least a good six cylinder block. Too much stress on a smaller motor & with the gas technologies today, you will burn the same or less with the larger 4-stroke. Just my two cents but the 175 Suzuki is light, actually just a cylinder motor, & a good fit. I'm out on this one but have at it.
2manyboats	posted 08-13-2013 09:22 PM ET (US) We had / have a 21 Revenge, with the Mercury 150 2 stroke it would run just shy of 50mph. We put a 130 Honda on it and it still ran mid 40s and we regularly ran it with 6 or 7 adults on board with no problem. Properly propped a 115 will work fine.
jimh	posted 08-14-2013 01:24 PM ET (US) I do not see the two choices offered as being equivalent. Compared to a 90-HP four-stroke-cycle engine, a 115-HP two-stroke-cycle engine will have 25-HP greater power, and it will probably be able to deliver better acceleration due to the excellent low-speed torque available from a two-stroke-cycle engine. An increase of 25-HP in a 90-HP engine represents an increase in power of 28-percent, which is a significant increase. It is also seen that engines of four-stroke-cycle design must reach very close to their maximum rated engine speed to develop their rated horsepower, while two-stroke-cycle engine tends to be able to develop their rated horsepower at lower engines speeds and to deliver that horsepower over a wider range of engines speeds. The result is that the two-stroke-cycle engine tends to out-perform the four-stroke-cycle engine in an application like an outboard engine for a boat. When the two-stroke-cycle engine has 28-percent greater horsepower rating, the difference between the two engines will be even more remarkable.
silentpardner	posted 08-17-2013 01:42 AM ET (US) [Moved to a separate discussion on a new topic.]