Does My Motor Look Too Low?

[upstatematt]

Hello! I've been a lurker here since I bought my pontoon boat in April and love the site and help. I'm learning about boats as I've never owned one and it seems like a huge learning curve. Long story short, my WOT rpms are about 5,200 on my 2003 Mercury four stroke EFI Bigfoot and before I change to a lower prop (currently have a 14x10, looking at going to a 14x9) I wanted to see if anyone thought my engine height could be a reason for the lower RPM's. The pontoon is a 1996 suntrack party barge 21'. The engine just seems pretty low to me, but I wanted to be sure before i adjusted anything. I really really appreciate all of the posters on this site and any comments you might have. I have attached a photo.
Thanks
Matt
Syracuse, NY
Oneida Lake

 

[rickdb1boat]

Re: Does My Motor Look Too Low?

Hi Matt. The motor looks way low to me. I see the transom is notched and that could be the reason. I would raise it up all the way to the bottom set of holes and try it again. What HP is your motor?

 

[Tony T.]

Re: Does My Motor Look Too Low?

I have a 1995 21ft Suntracker Fishin Barge with a 75hp Mariner outboard, my motor is mounted in the second set of mounting holes, at first I was wondering if mine was too high. About a week ago I tried the toon out for the first time and running a 13 3/4 x 15p aluminum prop I was seeing 22 + mph with my gps. My tach is messed up (may just need adjusted out, it has dial on back that I have not messed with yet). So I'm still experimenting at this point. Mine is the long shaft motor measuring 20". Is yours a 20" or 25"

Tony

 

[Underblog]

Re: Does My Motor Look Too Low?

Looks lower than mine. On mine the cav plate (horizontal surface above the propeller) is level with the waterline on the pontoons or maybe a bit lower. Perhaps your transom was adapted for a short shaft motor and then a long shaft motor was installed? Here is a picture of our pontoon for you to compare.

 

[upstatematt]

Re: Does My Motor Look Too Low?

Hey Rick, it's a 40hp model. What is a notched transom? I googled photos of transoms in relation to the cavitation plate and mine seems much lower than any photo I've seen. I'm getting a top speed of 17 unloaded, but at 5,200. I'd like to get about 300 more so RPMs I don't feel like I need a lower pitched prop to bog the motor and really think motor height is a factor. My cavitation plate isn't anywhere near the bottom of the transom, but about even to the bottom of my 25" logs. If it is lower than it needs to be, it could cause drag and lower my RPM's right? Tony, I'm not sure what to measure, i would assume it's a long shaft though?

 

[upstatematt]

Re: Does My Motor Look Too Low?

Does the bigfoot part make a difference with a 14" prop? I'm going to raise it tomorrow, i just want to make sure my setup isn't different or require more depth. Thanks again

 

[The Rooster]

Re: Does My Motor Look Too Low?

Welcome Matt. It does look a bit low, but hard to say until you see the cavitation plate while its running. The bigfoot is basically the lower unit from the 75-90-115 motor. good luck !!!

 

[Boss Hawg]

Re: Does My Motor Look Too Low?

Also quite a bit lower than mine-

 

[Triphammer]

Re: Does My Motor Look Too Low?

It seems some folks think setting the cav plate @ the bottom of the toons is the right move. Mine was set up with an extra long shaft motor (25") to get this effect while it looks like they notched your transom. I built a bracket, essentielly a fixed jack plate to raise my engine 8 inches & push it back 7". Now my cav plate is even =/- with the bottom of the motor pod. It hasn't raised my WOT or top speed like i had hoped but the propwash doesn't soak the backs of my deck like it had & I can stay clear of more of the rocks I had been hitting.

 

[Tony T.]

Re: Does My Motor Look Too Low?

My cavitation plate is not even with the bottom of the toons (mine is the 25" toons also) I have measured before with a level and for some reason I wantings to say 2 1/2" to 3" from the bottom of the toon I marked it, that mark is level with my cavitation plate. There again as I stated above my tachometer is messed up right now (erratic readings up and down) so I can't get a accurate rpm reading. Highest mph with the gps was 23.4 mph that day, with a 10-15 mph head wind,two people and gear probably totaling around 500# guessing, most speeds I recorded was 22+ mph. This was with a 75hp Mariner 4 cylinder.

Measure from the mounting brackets (top part of bracket that rest on top of transom) to the cavitation plate, that will give you your shaft size, mine was 20" and I also measured from mounting brackets to "center" of prop housing I came up with 27". These were the same measurments that the old motor (70hp Force) that was on the pontoon when I purchased it.

Tony

 

[Expidia]

Re: Does My Motor Look Too Low?

Just a comment that I think I'm right about this in that the Bigfoot Mercury model was designed for pontoons in that they need more torque.
So being that a Bigfoot has a lower gear ratio for torque, I don't think you will ever get the high end speed you might think you should be getting.

I'm sure someone will chime in if I'm wrong about the Bigfoot.

Can't comment on outboard height as I don't know what the proper Cav palte height for a toon shoud be. Try raising it a set of holes and water test it. That helped cut down on a lot of excess spray on my rig as the cav plate was riding too deep in the water when on plane. Now mine just skims the surface.

 

[Davem3]

Re: Does My Motor Look Too Low?

it looks like it is only off by a few inches, judging by the water scum marks in the picture...........
the end all cure is drop it in the water and measure from the cav plate to the surface, and subtract a few inches.......... under the cav plate MUST always be in water, it is where the water pump intake is ..........

a working tach is the cure all, end all though, it will let you know if you are in range or not ?????

and for giggles, GPS the speed as well???

 

[upstatematt]

Re: Does My Motor Look Too Low?

Hey all, thanks again for all the replies! Sorry it's taken me so long to reply. I was getting 16mph at 5,100 rpms with my boat. I'm going to attempt to raise the motor tomorrow and have a friend help me. My question is, do i need to build something to let the engine "rest" on at the top, or can it just be elevated with nothing between the motor top and transom. I took another photo tonight of the top, i just wanted to make sure I could simply raise it a few notches as is and not need to fabricate something. Also is a photo of the boat in action, is this the splash that I don't want?? I really appreciate everyones time in helping a newbee out. This might also explain the hard steering on it. It's something I've just gotten used to, but I wonder if thats contributing to it.

 

[BonairII]

Re: Does My Motor Look Too Low?

My question is, do i need to build something to let the engine "rest" on at the top, or can it just be elevated with nothing between the motor top and transom.

The motor is just fine being elevated above the transom.

I'm on Oneida Lake regularly....what part of the lake are you on?

 

[upstatematt]

Re: Does My Motor Look Too Low?

The motor is just fine being elevated above the transom.

I'm on Oneida Lake regularly....what part of the lake are you on?

I'm normally docked in West Monroe, Johnson Bay Marina. I was having other issues, so the boats in my yard now but it will be back tomorrow evening with luck. Gonna do it today...but it's 100 degrees outside! Where are you at?

 

[Tony T.]

Re: Does My Motor Look Too Low?

Hey all, thanks again for all the replies! Sorry it's taken me so long to reply. I was getting 16mph at 5,100 rpms with my boat. I'm going to attempt to raise the motor tomorrow and have a friend help me. My question is, do i need to build something to let the engine "rest" on at the top, or can it just be elevated with nothing between the motor top and transom. I took another photo tonight of the top, i just wanted to make sure I could simply raise it a few notches as is and not need to fabricate something. Also is a photo of the boat in action, is this the splash that I don't want?? I really appreciate everyones time in helping a newbee out. This might also explain the hard steering on it. It's something I've just gotten used to, but I wonder if thats contributing to it. View attachment 158957View attachment 158956

Hey Matt not trying to be smart "A" or anything but have you greased the steering cable lately. Also when I swapped out the motors on my pontoon I just used a engine hoist (cherry picker) it worked fine for me to position the motor where I needed it.

 

[upstatematt]

Re: Does My Motor Look Too Low?

Hey Matt not trying to be smart "A" or anything but have you greased the steering cable lately. Also when I swapped out the motors on my pontoon I just used a engine hoist (cherry picker) it worked fine for me to position the motor where I needed it.

Hey Tony, I did notice some grease fittings on the motor assembly and transom area, I'm going to grease those tomorrow. I also noticed an oil fill area for the power trim/tilt which I wanted to check tomorrow. I'm pretty new to boats, so don't think you are being insulting asking something that may be obvious to everyone else, but not me. There's a huge learning curve with boats. I noticed that the minute I thought I knew how to do something (anchoring) and I threw it in and drifted a 1/2 mile before I realized I did it wrong haha. 20' depth should equal 20' of rope throwout I thought.. haha. Yeah nothing is easy, but i'm slowly getting it.

I have a front end loader on my tractor with HD logging chain section already hooked up, just waiting my buddy to give me a hand. I was worried doing it alone, it might shift and damage all the cables going into the engine.
Matt

 

[Tony T.]

Re: Does My Motor Look Too Low?

Good deal, I use myself a good quality marine grease, hope it all works out for you, good boating and be safe.

Tony

 

[Silvertip]

Re: Does My Motor Look Too Low?

Someone mounted this engine that didn't know what they were doing. YOu cannot raise the engine unless you drill new holes for the lower two mounting bolts. It appears to me that the original wood portion of the motor pod has been removed -- possibly because this is a short shaft motor. They then possibly added a 14 inch prop on a 1.83 (non-bigfoot motor). Measure the shaft length and let us know whether you have a BigFoot or standard lower unit. If it is a BigFoot it will say so on the cowl. BigFoot mtors have 2.34 gears where a standard unit has 1.83 gears. Mounting holes should be spaced so you can raise or lower the motor without drilling new holes. The motor was set so low because "ventillation" (not cavitation) was an issue. The power head itself must sit really close to the water line which simply is not right.

 

[BonairII]

Re: Does My Motor Look Too Low?

Where are you at?

I launch at Oneida Shores. My son and I normally fish anywhere from the Brewerton bridge area up to Lower South Bay.