Bass Boat with long shaft motor?

[poor_boy67]

Hi folks, I need help determining if I have a long shaft motor on a short transom boat and what I can do about it if this is the case. I purchased this boat about 2 months ago and other than having to replace the trim motor everything seems to work great, however people started telling me the the boat should run faster than what it does. I have an 1982 chanpion 18'6 FS that has a 1989 Force 150 motor. After looking around nobody in the world has a Force on the back of their bass boats and they appear to be only on the deep v type pleasure boats. Anyway top speed was about 42 mph so I started playing with this thing and it has a hydrofoil on it so I removed it boom I jumped up to 47 mph but my boss at work says that it still should run close to 60 with the 150 on it. So after looking around several different forums it appears that I might be dealing with a long shaft motor on a short transom boat especially since removing the hydrafoil I jumped up 5 mph which makes me think that while running at WOT that this thing was still completely submerged. Another indicator is that to get maximum speed I have to run with the trim all the way up and when I stop I get a good amount of water that comes over the back of the boat I seen that in another post somewhere. If this is the case would putting a jackplate on to lift the motor to where the prop is supposed to run be something to look at? My concern is ofcourse with a long shaft motor will this be too much torq on the transom or be less torq on it due to lifting the prop up. The boat is rated for a 175 hp which may be enough rating to lift this 150 5 to 6 inches and still be okay. I'm new to this and seems like I can't learn fast enough any help would be appriciated. I've attached pictures so you can see what I'm talking about just in case I'm barking up the wrong tree.

 

[Miroash]

Re: Bass Boat with long shaft motor?

The first thing I noticed is your motor already looks a little high. I may be looking at the photo wrong but the cavitation plate is normaly even with the bottom of the transom +/- a few inches yours looks like it's about 4-6 inches above the bottom. I dont know if you should raise it anymore, if anything I think you have an xtra long 25" transom with a 20" long motor. Maybe someone with more experiance will chime in to correct me.

 

[poor_boy67]

Re: Bass Boat with long shaft motor?

The way I understand it from reading other posts is that the prop shaft is supposed to be +/- 1in with the bottom of the boat on bass boats hence the notched transom to allow the water level to return far enough to maintain cooling and prop push. Looking on bass boat central and scream and fly forums thats kinda the idea I'm getting and my propshaft is about 4 to 5" below the bottom of the boat.

 

[Miroash]

Re: Bass Boat with long shaft motor?

The way I understand it from reading other posts is that the prop shaft is supposed to be +/- 1in with the bottom of the boat on bass boats hence the notched transom to allow the water level to return far enough to maintain cooling and prop push. Looking on bass boat central and scream and fly forums thats kinda the idea I'm getting and my propshaft is about 4 to 5" below the bottom of the boat.

I am not familiar with how "Bass Boats" are set-up (I have never owned one), I was not aware they were set-up differently. You may very well be correct.

 

[jeff_smith_0423]

Re: Bass Boat with long shaft motor?

Your setup actually looks ok to me. I wouldn't expect 60mph out of an 18'6 boat and a 150 Force. If it was an OMC motor, maybe 50-55 with a stainless prop, and perfect setup. 47 sounds respectable to me. I'm not trying to badmouth the Force motors, but I've always percieved them as "less powerful" and "less modern" than their OMC/Japanese/TrueMercury cousins of the same rating.

 

[poor_boy67]

Re: Bass Boat with long shaft motor?

After about 2 weeks of research and messing around with the boat this is what I come up with. It looks as though common starting point for setup is for the prop shaft to be 3 1/2 inches below the bottom of the boat and then start lifting the motor from there generally with a jack plate moving the motor back and lifting for every 12 inches the motor is moved back it is supposedly be able to raise it 1" and maintain good contact with the water. At any rate my prop shaft was 5" below the bottom of the boat so I raised it 1". My current performance is 44mph at 5800 rpm WOT but I believe that the cavitation plate is still submerged under water at full speed. I think that I need to change from a 21" prop to a 23" and it will bring my rpm down into the recomended range of 5000 to 5500 for WOT. I'm not sure of how I can raise the motor anymore without a jackplate unless someone knows of any other type of spacer I wasn't really looking to put a jackplate on as it looks as though they are predrilled for the standard motor mounts which this Force doesn't have. I'm also having a hard time trying to find a 23" SS prop for this motor. The motor runs out great with 150 lbs. of compression across the board and I believe for the type of boat that it is on I should be able to break at least 50 mph I'm just having problems with the setup on it. No aftermarket manufacturers appear to make a 23" prop for this motor.

 

[sschefer]

Re: Bass Boat with long shaft motor?

The bottom of the cavitation plate should be level with the transom step to guarantee water pickup it looks like raising it an inch probably got you there. However, you can cheat the devil and maybe get a couple of more mph out of it with a hydraulic jack plate.

The question is, is it worth it. Are you a pro tourney fisherman that needs to beat the other guy to the hole. No, not with your boat and motor. Relax, 45 mph is plenty to get you down the lake and fishing.

I'm probably not the best one to give advice on what you need and what you don't, I have a 17'9" V-Hull that does 56 with a E-Tec 115 HO. Don't even ask what the price of those extra mph's were. LOL...

 

[poor_boy67]

Re: Bass Boat with long shaft motor?

The question is, is it worth it. Are you a pro tourney fisherman that needs to beat the other guy to the hole. No, not with your boat and motor.

Your correct I'm just an everyday joe that would like to get the best performance out of what I got. Thing is I believe that with the proper tweaking in the right places and can make this combination crack 50 mph if for no other reason but to be a learning experience. Either it can be done or it can't this will help me learn what works and what don't. I believe if I get the right combination on the setup I will get the most speed, best handling and more fuel efficiency. Thats all I'm looking for, granted I didn't spend 10K on this used jewel. I've got a good boat with a decent running motor I just believe the setup is off.

 

[sschefer]

Re: Bass Boat with long shaft motor?

Got ya, well then keep tinkering. You can get that prop pretty close to the surface and still get really good bite. The thing you have to be very careful of is ventilation which might cause sudden over reving and also not enough of the water pickup in the water which will cause over heating. There is a sweet spot you just have to keep playing with it until you find it.

You also want to be mindful of how it acts in turns.

 

[steelespike]

Re: Bass Boat with long shaft motor?

You may be able to get your prop repitched and perhaps tweaked a little.
You might post in the prop section also in the chrysler force section.
You may find some tricks and perhaps some informed opinions on wheather
your motor is up to it.