Outboard Height ?

[kero]

Hi,

I have changed motors from a 50 2st merc to a 60 4st merc. on a 4.8 Stacer tiller steer.

The reason was for more grunt as i cross bars such as SW Rocks for all my fishing.

The 50 was set up perfectly, on to plane quickly just a little under power when encountering

pressure waves on a runout. The 60 takes a lot longer to plane. It sprays water badly untill it is

trimmed right up. My question is could it be set up too low? I run a 13 prop. will a change of prop

plane quicker? The trimming of the 50 was never an issue, the 60 requires trimming constantly.

Edited March 22, 2009 by swordfisherman

[Geoff]

Check the height of the cavatition plat in relation to the bottom of the transom.

The top of the plate should be either in line with the bottom of the transom or perhaps a few mm below

Geoff

[Yarraone]

I could be wrong but I did not notice any Hydrofoil wings? I had the same problem once and they helped so much i dont put a motor on now without them

Edited March 22, 2009 by yarraone

[WANNAFISH]

Looks like its a bit low. If you can go level on the keel to the cav plate or another 25mm up from the keel.

[Flightmanager]

Hi,

I have changed motors from a 50 2st merc to a 60 4st merc. on a 4.8 Stacer tiller steer.

The reason was for more grunt as i cross bars such as SW Rocks for all my fishing.

The 50 was set up perfectly, on to plane quickly just a little under power when encountering

pressure waves on a runout. The 60 takes a lot longer to plane. It sprays water badly untill it is

trimmed right up. My question is could it be set up too low? I run a 13 prop. will a change of prop

plane quicker? The trimming of the 50 was never an issue, the 60 requires trimming constantly.

Without trying to buy into the 2 stroke vs 4 stroke debate , a 60 HP 2 stroke will outperform a 60 HP 4 stroke .

Consider the extra weight of the new motor , and if you were to look at the torque curve for the 2 motors , you will find that the 2 stroke is streets ahead. A 60HP 2 stroke " clean " engine ( Etec , Opti) 2 stroke will offer more power , torque , and fuel useage will be very similar.

As for the trim issue , if you are achieving the optimal RPMs for your engine at WOT ( Wide Open Throttle ) then your choice of prop is probably correct. I would suggest that if you trimmed the motor lower until you were on the plane , then trimmed it up to increase prop RPMs at cruise speed , you would not see the problems that you have mentioned . Lower trim = more pushing power. Higher trim = higher prop speed , but less torque.

Ross

[glennmreid]

I used to have a 60 HP 4 stroke Merc as well, on my 4.50 Bermuda runabout. Huey will be able to answer regarding the high issue. I had the same issues regarding performance. It took a while for the boat to plane properly, and I really out to trim the motor out to get the boat on the move. Once the boat was going, then I slowly trimmed up. The performance issue was why I got rid of my 4 stroke merc and changed to a 60 HP E-TEC.

I think the prop size is ok, but you will notice that changing from a 2 stroke to a 4 stroke, the low down torque isn't really there with the 4 stroke. You will also probably notice it isn't until the motor hits around 4000rpm before you really see it on the move.

[pelican]

Did a dealer or mechanic fit the motor? If that motor is set on the same holes as yout old one have you bought the same shaft length motor?

Photos can be decieving.

My thoughts are the it seems 50mm too low. The cav plate ( flat plate just above prop) should have it's lower side just above a straight line extending from the bottom planing of the hull as a starting point. The lift will stop the lower unit drag and give better holeshot , quicker plane and better top speed.

Once at the correct height , sort out your WOT and get your prop right.

People who deal with this every day will suggest the probable correct pitch, style of prop and set up.

Avoid all wings , permatrins , laserfoils etc until your set up is sorted and then if you have a specific issue possibly look at them but they can have many more issues than what they solve.

[Davemmm]

Without trying to buy into the 2 stroke vs 4 stroke debate , a 60 HP 2 stroke will outperform a 60 HP 4 stroke .

Consider the extra weight of the new motor , and if you were to look at the torque curve for the 2 motors , you will find that the 2 stroke is streets ahead. A 60HP 2 stroke " clean " engine ( Etec , Opti) 2 stroke will offer more power , torque , and fuel useage will be very similar.

As for the trim issue , if you are achieving the optimal RPMs for your engine at WOT ( Wide Open Throttle ) then your choice of prop is probably correct. I would suggest that if you trimmed the motor lower until you were on the plane , then trimmed it up to increase prop RPMs at cruise speed , you would not see the problems that you have mentioned . Lower trim = more pushing power. Higher trim = higher prop speed , but less torque.

Ross

I think a little bit of the weight to torque dissapear when you realise he goes from a 50 HP 2 stroke to a 60hp 4 stroke.

No expert here but I believe the extra bit of grunt in the motor outways the 2/4 stroke argument.

Dave

[Flightmanager]

I think a little bit of the weight to torque dissapear when you realise he goes from a 50 HP 2 stroke to a 60hp 4 stroke.

No expert here but I believe the extra bit of grunt in the motor outways the 2/4 stroke argument.

Dave

A 4 stroke of slightly higher horsepower will eventually outpace a slightly smaller 2 stroke , but for " out of the hole " performance , its the 2 stroke . In a side by side test , the 2 stroke will get up on the plane quicker ( higher torque) , but will fall behind slightly above planing speed ( higher horsepower) .

Ross

[kero]

Many Thanks for the replies. The change of motors was strictly for grunt. When i enquired about a 60 2st

I was offered the 60 4st for an extra 350.00 so i went with the 4.

The motor will be raised one notch on monday, hoping that will eliminate the spraying of water all up the transom. I can live with the slower hole shot. I must admit it goes like a scalded cat and grunt is there if and when needed.

Kero.

[a boat]

Many Thanks for the replies. The change of motors was strictly for grunt. When i enquired about a 60 2st

I was offered the 60 4st for an extra 350.00 so i went with the 4.

The motor will be raised one notch on monday, hoping that will eliminate the spraying of water all up the transom. I can live with the slower hole shot. I must admit it goes like a scalded cat and grunt is there if and when needed.

Kero.

Hi, set-up and propped correctly a 60HP Mercury 4-Stroke will offer similar "grunt" to the 50HP 2-Stroke, but looking at your photos you have the small gearbox 60HP Mercury and really the dealer should of pointed you in the direction of the "big foot" 60HP Mercury, which easily outperforms the small gearbox that you have. I would raise it a hole and you want to see about 5800 at WOT with your normal load and if so you have the right pitched prop.

Do not except any more grunt from what you have done, having more weight and the small gearbox counter acts any performance gain, especially down low, you might see going from 50HP 2-Stroke to 60HP 4-Stroke, but it does look a little low and running a SST prop can have the engine higher.

Cheers,

Huey.

[DDDave]

I had a look at my Merc 60HP on Stacer 469 easy Rider to compare and yours does look fairly low.

With the 13 pitch prop at WOT you will get 35mph out of it.

My boat is similar size and with the motor set up right properly pitched prop etc with wifey and 3 kids stowed away it punches along a treat. Often have a couple of kids in the ski tubes hanging off the back and does the job pretty well for what is after all a mid size motor.

get it set up right and you will be happy..

[pelican]

I had a look at my Merc 60HP on Stacer 469 easy Rider to compare and yours does look fairly low.

With the 13 pitch prop at WOT you will get 35mph out of it.

My boat is similar size and with the motor set up right properly pitched prop etc with wifey and 3 kids stowed away it punches along a treat. Often have a couple of kids in the ski tubes hanging off the back and does the job pretty well for what is after all a mid size motor.

get it set up right and you will be happy..

Hey dave do you have the bigger gearbox?

[DDDave]

Hey dave do you have the bigger gearbox?

No the same as this one. I think the big foot is fairly popular in the USA for pushing houseboats and barge type set ups.

[a boat]

Hi, the bigfoot is popular here too for getting the most out of the Mercs. On any boat the gear ratio and bigger diameter props allow for better grunt out of the hole in particular and 4-Strokes tend to benefit the most. Yes on a very light weight ski boat I would recomend the small box for best outright speed it turns a smaller prop quicker, but for 90% of boats the "bigfoot" performs better and the extra cost of about $200 to go to the "bigfoot" is worth it and it is the same box that 115HP runs thru so it is never stressed with only 60HP running thru it.

Cheers,

Huey.

[DDDave]

Hi, the bigfoot is popular here too for getting the most out of the Mercs. On any boat the gear ratio and bigger diameter props allow for better grunt out of the hole in particular and 4-Strokes tend to benefit the most. Yes on a very light weight ski boat I would recomend the small box for best outright speed it turns a smaller prop quicker, but for 90% of boats the "bigfoot" performs better and the extra cost of about $200 to go to the "bigfoot" is worth it and it is the same box that 115HP runs thru so it is never stressed with only 60HP running thru it.

Cheers,

Huey.

Cool. Dont see them down here in Taz, only ever seen the standard gearbox models.

I guess I am not alone in not really understanding gear ratio, prop diameter and pitch and how it all relates to power. My crappy basic calcualtions tell me running a 13 pitch prop on the 2.33 gearbox would drop top end speed by some 13 or 14 Kmh at same RPM. So would need to fit a 17 pitch to pull the same speed wide open. I guess thats what makes it quicker out of the hole, having a greater pitch on the prop? and I guess a larger surface area (diameter) helps as well. Very interesting this stuff really.

None the less the hole shot on the 1.83 gearbox with a 13 pitch prop would still mess up Donald Trumps hair, and that is good enough for me. cheers guys.