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Author Topic:   Advice on Repowering 13' with 25hp Honda

mojack posted 07-21-2003 09:07 PM ET (US)
I am going to be repowering my 13'er with a 25hp Honda. From what I've gathered, it weighs only 15# more than the motor that is on there now. I'll probably move the battery under the forward thwart for compensation. I think one of the main things I want to know is where the Anticav plate should be inreference to the bottom of the transom. I've seen where others here have raised the motor 1 to 1.75 inches for improved performance. I didn't know if this should be done on the 13s also. I did notice that when I adjusted the trim bolt back (to raise the bow a little) it cavitated (I think) just before I could get it to plane. I did have my wife and 3 small kids on board when it did that but my wife and I were aft and the kids were forward. When I moved the trim bolt back to the center hole it never did that again. I wasn't sure if raising the motor may make that problem worse or improve it. Any advice will be greatly appreciated as usual.
-Derek
mojack posted 07-23-2003 08:15 PM ET (US)
bump bump
Jamie 20 outrage posted 07-23-2003 11:32 PM ET (US)
It is hard to answer your questions without knowing what kind of water you are running on. The rougher the water, the lower the engine on the transom. You have to balance the height of the engine with the amount of trim, with the ability to get on a plane easily, with the trim of the boat at planing off speeds. There is no specific numbers that will work since there are too many variables. Start with the lower cav. plate in line with the bottom of the boat and you have a good starting point.
mojack posted 07-24-2003 08:12 AM ET (US)
That's a good point. The water here gets rough and choppy. The motor on there now is all of the way down on the transom and it does fine so I'll probably mount the new motor the same way.
Thanks
David Jenkins posted 07-24-2003 09:10 PM ET (US)
If you have not yet made the purchase, consider hanging the 50 hp Honda on the transom. With no jack plate, it weighs just over 200 pounds, which is not too heavy for that boat. You can then pull a skier and will never be short on power. Otherwise, there will be times when you will wish you had more umph.
mojack posted 07-24-2003 09:45 PM ET (US)
I bought the motor last year for a 2700 (plus tax, install and battery). It's those hidden costs that get you. When I walked out the door with the receipt, the motor cost $3700! I can't imagine a 50hp motor on the back of that little boat! I bet the prop is the only thing touching the water when your at full throttle! Thanks for the input.
David Jenkins posted 07-25-2003 09:02 AM ET (US)
To answer your question about the height of the engine, Clark Roberts has made a good argument that higher is better as long as the water intake remains underwater and you do not plan to be running at full throttle in heavy seas.
DCM posted 07-25-2003 12:21 PM ET (US)
I have a 50hp Merc 2-stroke on my 1985 super sport. Took it out for the first time last night and at 5,000 rpm it does around 30 mph (going by the speedo gage)
Dan
GlennGlenn posted 07-25-2003 01:45 PM ET (US)
Dave Jenkins says: "If you have not yet made the purchase, consider hanging the 50 hp Honda on the transom. With no jack plate, it weighs just over 200 pounds, which is not too heavy for that boat. You can then pull a skier and will never be short on power. Otherwise, there will be times when you will wish you had more umph."
I agree Dave, it seems to me that the 25 HP Honda is NOT enough for the 13 SS. I have a 50 HP JohnRude on mine (2 stroker) and she'll do 45 all day long. Mounted her up high and with PTT, I can adjust the angle of attack for water conditions. Into the wind, the only thing in the water is the prop and maybe 4 inches of boat in the rear.
Glenn
Englewood, FL
mojack posted 07-25-2003 02:34 PM ET (US)
Thanks for all fo the input. I think the 25 Honda will be more than adequate for what I need it for. I plan on getting a bigger boat in a few years as the kids get bigger and I'll make sure it has enough power to pull them around.
Derek
David Jenkins posted 07-25-2003 02:38 PM ET (US)
A 50 hp Honda on a 13' Whaler is a perfect combination, especially if you can put a low-profile 12-gallon tank under the forward thwart. If you carry fuel in the stern and/or if you use a jackplate it becomes too back-heavy. Otherwise, it's great.
We have a 25 hp engine on our 11', and that works out well for us.
I like to have enough horse power so that I do not have to run wide open all the time. And I like to be able to load a lot of people and gear on the boat and still be able to get on a plane.
Also, engines tend to lose power as they age, so if you have a plethora of power with the new engine, it may still be a good setup 10 years from now.
quickfarms posted 07-25-2003 04:13 PM ET (US)
I believe that until about 1986 the horsepower of a ouboard was rated at the flywheel and after that the horsepower was rated at the prop. I have also heard that the regultions allow for a variance of plus or minus 5 percent.
At this time the horsepower of the outboards was redefined. A johson 35 became a 30 and the 50 became the 40 but I do not believe that the max horsepower rating of the 13 whaler was changed. If the max Horsepower rating was that critical we would have seen it reduced.
So because of this change in the regulations you can over power a boat legally and because of the allowable error in the rating you may actually have overpowered your boat if you have a pre 1986 boat with a post 1986 outboard on the back.


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Author	Topic: Advice on Repowering 13' with 25hp Honda
mojack	posted 07-21-2003 09:07 PM ET (US) I am going to be repowering my 13'er with a 25hp Honda. From what I've gathered, it weighs only 15# more than the motor that is on there now. I'll probably move the battery under the forward thwart for compensation. I think one of the main things I want to know is where the Anticav plate should be inreference to the bottom of the transom. I've seen where others here have raised the motor 1 to 1.75 inches for improved performance. I didn't know if this should be done on the 13s also. I did notice that when I adjusted the trim bolt back (to raise the bow a little) it cavitated (I think) just before I could get it to plane. I did have my wife and 3 small kids on board when it did that but my wife and I were aft and the kids were forward. When I moved the trim bolt back to the center hole it never did that again. I wasn't sure if raising the motor may make that problem worse or improve it. Any advice will be greatly appreciated as usual. -Derek
mojack	posted 07-23-2003 08:15 PM ET (US) bump bump
Jamie 20 outrage	posted 07-23-2003 11:32 PM ET (US) It is hard to answer your questions without knowing what kind of water you are running on. The rougher the water, the lower the engine on the transom. You have to balance the height of the engine with the amount of trim, with the ability to get on a plane easily, with the trim of the boat at planing off speeds. There is no specific numbers that will work since there are too many variables. Start with the lower cav. plate in line with the bottom of the boat and you have a good starting point.
mojack	posted 07-24-2003 08:12 AM ET (US) That's a good point. The water here gets rough and choppy. The motor on there now is all of the way down on the transom and it does fine so I'll probably mount the new motor the same way. Thanks
David Jenkins	posted 07-24-2003 09:10 PM ET (US) If you have not yet made the purchase, consider hanging the 50 hp Honda on the transom. With no jack plate, it weighs just over 200 pounds, which is not too heavy for that boat. You can then pull a skier and will never be short on power. Otherwise, there will be times when you will wish you had more umph.
mojack	posted 07-24-2003 09:45 PM ET (US) I bought the motor last year for a 2700 (plus tax, install and battery). It's those hidden costs that get you. When I walked out the door with the receipt, the motor cost $3700! I can't imagine a 50hp motor on the back of that little boat! I bet the prop is the only thing touching the water when your at full throttle! Thanks for the input.
David Jenkins	posted 07-25-2003 09:02 AM ET (US) To answer your question about the height of the engine, Clark Roberts has made a good argument that higher is better as long as the water intake remains underwater and you do not plan to be running at full throttle in heavy seas.
DCM	posted 07-25-2003 12:21 PM ET (US) I have a 50hp Merc 2-stroke on my 1985 super sport. Took it out for the first time last night and at 5,000 rpm it does around 30 mph (going by the speedo gage) Dan
GlennGlenn	posted 07-25-2003 01:45 PM ET (US) Dave Jenkins says: "If you have not yet made the purchase, consider hanging the 50 hp Honda on the transom. With no jack plate, it weighs just over 200 pounds, which is not too heavy for that boat. You can then pull a skier and will never be short on power. Otherwise, there will be times when you will wish you had more umph." I agree Dave, it seems to me that the 25 HP Honda is NOT enough for the 13 SS. I have a 50 HP JohnRude on mine (2 stroker) and she'll do 45 all day long. Mounted her up high and with PTT, I can adjust the angle of attack for water conditions. Into the wind, the only thing in the water is the prop and maybe 4 inches of boat in the rear. Glenn Englewood, FL
mojack	posted 07-25-2003 02:34 PM ET (US) Thanks for all fo the input. I think the 25 Honda will be more than adequate for what I need it for. I plan on getting a bigger boat in a few years as the kids get bigger and I'll make sure it has enough power to pull them around. Derek
David Jenkins	posted 07-25-2003 02:38 PM ET (US) A 50 hp Honda on a 13' Whaler is a perfect combination, especially if you can put a low-profile 12-gallon tank under the forward thwart. If you carry fuel in the stern and/or if you use a jackplate it becomes too back-heavy. Otherwise, it's great. We have a 25 hp engine on our 11', and that works out well for us. I like to have enough horse power so that I do not have to run wide open all the time. And I like to be able to load a lot of people and gear on the boat and still be able to get on a plane. Also, engines tend to lose power as they age, so if you have a plethora of power with the new engine, it may still be a good setup 10 years from now.
quickfarms	posted 07-25-2003 04:13 PM ET (US) I believe that until about 1986 the horsepower of a ouboard was rated at the flywheel and after that the horsepower was rated at the prop. I have also heard that the regultions allow for a variance of plus or minus 5 percent. At this time the horsepower of the outboards was redefined. A johson 35 became a 30 and the 50 became the 40 but I do not believe that the max horsepower rating of the 13 whaler was changed. If the max Horsepower rating was that critical we would have seen it reduced. So because of this change in the regulations you can over power a boat legally and because of the allowable error in the rating you may actually have overpowered your boat if you have a pre 1986 boat with a post 1986 outboard on the back.