7.5hp Gamefisher..........how fast?

[Warlord]

I have a 7.5hp 1979 Gamefisher on my 10ft. aluminum boat. I was wondering how fast it should go. The boat itself weighs probably about 200 lbs. And me at 240. According to my GPS it only goes about 5 mph, maybe just under 6 if I am lucky and thats if I sit in the middle.

 

[AuSable Junkie]

Re: 7.5hp Gamefisher..........how fast?

I had a 12' Sears gamefisher with a 6 hp Johnson on it. I weigh about 180.
I clocked it with the gps at about 15-16 mph.

 

[Lion hunter]

Re: 7.5hp Gamefisher..........how fast?

Had a 5hp on a 12' and it would move around 8-10. A 7.5 should be around 10-12.

 

[5150abf]

Re: 7.5hp Gamefisher..........how fast?

I would geuss your engine needs some attention, get a manual(OEM) and a carb kit and get to work.

 

[Warlord]

Re: 7.5hp Gamefisher..........how fast?

Well I guess there is definitely a problem since it sounds like I should be getting more out of the motor. I have taken the carb off and plan to go through it, but it seems to have run fine before. I am also raising the motor up on the transom to see if that will help. So as soon as the carb is done its back to the lake to try again. Any other suggestions?

 

[Warlord]

Re: 7.5hp Gamefisher..........how fast?

Okay so I cleaned out the carb, reset the float level, checked the reeds and everything is all clean and nice now. I put on a new gasket when I put the carb on and guess what?. It was running fine but still didn't seem ro be running quite right. It was running like it was a little rough. Sprayed some carb cleaner around the base of the carb and it died. So should I double up the gasket. Then with my usual luck it was running then died and I couldn't get it running again it was flooding out. I took off the carb to find out the fuel pump element was torn, it is one thing after another. I am starting to see why people don't keep these motors. I have a 5 HP Gamefisher but it is ten years newer than the 7.5, maybe I should just enjoy going slow,lol.

 

[Capt Ron]

Re: 7.5hp Gamefisher..........how fast?

I have a 4hp Sears and a 3hp Johnson that I use on my 9' Avon. The Sears will slowly plane the boat whereas the Johnson planes as soon as I move forward.

Having run several of these low dollar, entry level Sears type motors over the years I have found that they generally can't live up to the power claimed. Maybe as much as 1/3 less hp. Learned not to go farther from the landing than I could paddle back after the motor quits. These are the most tempermental motors ever sold.

One day I got crazy and put both motors on the Avon...It hauled azz but was a hand full since the Sears would cavitate if not lined up with the other motor. Also, the Sears has a throttle lever as opposed to the Johnson with the tiller throttle so I needed three hands, two to control the motors and one to hang on for dear life.

The best plan is to sell your 7.5 and 5 and put that money into a twin cylinder OMC motor with a 3 bladed prop. I'll bet that your boat would go a lot faster with a motor of like hp. Not only that but it would be more reliable, quieter, and use less fuel. Plus, repairs and parts willl be easier to obtain.

Once you get rid of that TW you will never go back!

Capt Ron

 

[Warlord]

Re: 7.5hp Gamefisher..........how fast?

Yeah I am really starting to think about getting rid of the motors and putting the money towards another one. The 5HP is is excellent shape and runs wonderfully but it is still a 5hp, but I got it from this guy who couldn't get it running for 30 bucks, and all I had to do was clean the points. The 7.5 is in really good shape too and has good compression and gears plus I have another one that is all beat up that I use for parts. It runs too, just ugly as sin, lol. I don't think I will try putting both on at once though.They both have tiller throttle, and a 3 blade prop, but I only have so many hands. Still I am going to finish fixing up the 7.5 and starting looking for something else, since it just sounds like these motors just don't have the power.

 

[fishrdan]

Re: 7.5hp Gamefisher..........how fast?

I had an 80's Sears 5HP and an early 70's Sears/Ted Williams 7.5HP outboard, they both performed the same. 7.5HP was a gutless piece of....

 

[lowkee]

Re: 7.5hp Gamefisher..........how fast?

You may need some ballast up front. Any chance of moving the fuel tank forward? For such a short boat your weight will cause some severe plowing with just a 7.5. I used to have that same motor on a 14' and with two people it would plane out nicely, but you could see where you were going with just me. Have a second person ride up front to see if you can plane out. I think it may simply be a big guy in a little boat. A 15hp would fair better for you, but I'm not sure a 10' can handle one.

 

[Capt Ron]

Re: 7.5hp Gamefisher..........how fast?

Let's see...I paid $10 for the Sears at the flea market. For less than $20 in parts it runs like a top, Well at least as good as it was designed. It's a 1967.

The Johnson cost me $50 the next week at the same flea market and I had to rebuild the lower unit which cost me $80. Then I find that the little fuel pump bladder in the carburator was bad so with shipping $18. Total $148.

Rats, now I gotta light the grill, it's too hot for that...

Capt Ron

 

[Warlord]

Re: 7.5hp Gamefisher..........how fast?

Well I have tried it with someone up front and it still really didn't have any power. Also using the GPS the speed between the 5 and the 7.5 was only like one mph different. Being that the 5 is ten years newer than the 7.5 I think it was made better, also by force and not eska. My friend has a 14 foot aluminum boat heavy as crap with a merc 20HP 4 stroke. With me and him in it the thing goes around 20 + mph. I am going to try raising it up on the transom, cause the measurement from the mount to the cavitation plate is 16 1/2 inches. When mounted on the boat the cav. plate is about 2 inches lower than the bottom of the boat. Oh and as far as moving the fuel forward I have tried it with just its internal tank and no difference.

 

[Capt Ron]

Re: 7.5hp Gamefisher..........how fast?

I figure that your pushing about 500# with 7.5hp and that's 66.666#/hp.
Given the wetted surface then you could actually do better with a boat of more length and/or beam. Right now the boat is in displacement and can't rise enough to get on a plane. The reason that you only got a mph difference between the to engines points out the beauty of a displacement hull, takes little hp to reach the design speed (which the 5hp did). Forcing the boat to go faster only wastes power and fuel. Adding more weight as bow ballast will not help in this situation.

I weigh 212# and I'm amazed that 3hp can plane me in a rubber boat, it is rated for 8hp...that's what I'm looking for now.

Capt Ron

 

[fishrdan]

Re: 7.5hp Gamefisher..........how fast?

using the GPS the speed between the 5 and the 7.5 was only like one mph different

That's the same experience I had, maybe a touch better, but not 50% more power.

I bought a 14' jon boat and tried both of those outboards, both would plane the 1436 jon boat, but nothing impressive. I sold both of them and bought a 7.5 Force (sears) and the 1436 jon boat flies, it will even plane me, another adult and all of our carp, max load, somewhere around 660#. With just me onboard it goes just fine, 20MPH+.

I do agree that it might be a problem with the hull design/size, weight and weight distribution. I used to have the 5HP Force (same as yours) on a Coleman Crawdad and it would plane and go fast, but weight distribution was very important. I sold the Crawdad and bought a WaterTender 9.4, that hull was a pig and wouldn't plane out, 5-7MPH tops. Had it for a year and bought the 1436 jon boat. The same 5 HP outboard would plane the long jon boats, but not the short cathedral hull (tri-hull) boat.

Have you checked to see if the keel of the boat is straight, not hooked or bowed out/down, and the bottom side is straight with no big dents?

 

[Warlord]

Re: 7.5hp Gamefisher..........how fast?

Wow there are so many variables to try to figure into this whole boat situation. As far as the size of the boat at its widest point is about 5 feet. When it sits in the water by itself the bow really sits on top of the water. The way it is shaped it really seems to float on the surface, but the transom when I am in it does get low. Take a look at this link and you will see what the boat looks like. It was a project and I still have never posted the final pics, but you can see what I am dealing with. Thanks for all the info so far from all of you. Also take a look at the pieces someone added to the back of the boat, what the heck is their purpose?

http://forums.iboats.com/showthread.php?t=225499&page=11

 

[Capt Ron]

Re: 7.5hp Gamefisher..........how fast?

The extra pieces are trim tabs, maybe some else was having the same problem and installed those to push the bow down. They also increase the surface area. You can try to lower the aft edge but be careful as tooo much can make the boat a little squirrely.

Capt Ron

 

[Warlord]

Re: 7.5hp Gamefisher..........how fast?

Somehow to me they don't seem to be trim tabs. They don't move at all and are flush and level with the bottom of the boat. Also the way they are empty inside, they just seem to create more drag. I figured there were steps to help get in the boat if you were in the water. Underneath they are reinforced along the entire length of the boat not just at the transom, and that would be pointless for a trim tab. Thats a lot of work riveting from transom to bow, for the 4 pieces of "L" angle that was put on. Thats why I think steps so it won't tweak the transom from the weight. I know they are not original so most likely I am chopping them off. I had even tried filling the cavity with styrofoam but that didn't help.

 

[Capt Ron]

Re: 7.5hp Gamefisher..........how fast?

There's all different kinds of trim tabs, not just the moveable or adjustable types. By bending the center of the horizontal section up and pushing down on the aft edge you should be able to lower the edge a little. Or better yet, do I see a strip extending aft on the bottom of the transome between the tabs? Tweak that down a little bit, getting more lift there could help get the stern up and the bow down enough to accelerate to a plane.

Capt Ron

 

[Warlord]

Re: 7.5hp Gamefisher..........how fast?

Well there used to be a strip between the tabs, but I removed that many months ago when I rebuilt everything. It was in the way of the motors. I have a minn kota on the back plus the 7.5 but with the way the motors mounted they hit the piece that was in the middle which is why it was all bent out of shape. Also there is no way to bend anything as the "L' angle that was put in comes all the way aft supporting the so called trim tabs or steps. Maybe I will just redo the trim tabs and make two long ones. At least then they will be adjustable I have some hinges and aluminum that I can do it with. From what you are saying though it sounds like it won't take a lot of down trim to maybe get the boat up on plane. Oh yeah, would it be easier to just put a Doel-Fin on the motor or would trim tabs be better.

 

[Lion hunter]

Re: 7.5hp Gamefisher..........how fast?

Now that I read the other post and seen what kind of boat you have, I think I know your problem. It's the boat. I have the same boat in a 12'. They are very particular about weight distribution, and very slow to get on plane if overloaded. I'm 185lbs and I run a 9.5 johnson. With just me in the boat I have to have about 50-60lbs in the front to jump on plane. If the weight is even in front and back it will plow. Short answer is that they are a great stable fishing boat, but not the most effecient hull design.
I don't think it matters what you do that gamefisher will not have the power to over come that hull design and plane that boat unless you have the weight perfect.