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Evinrude 25hp top speed problems

Get a marine tach that runs off of your charging system. There should be a plug on your control box battery pos, neg and signal from the stator. Then you set the switch on the back of the tack to 6 poles. That is of course if you have the charging system on that engine. That would be a nice upgrade you said you connected controls and steering is it an electric start?
 
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Hi all thanks for all your reply's....

KevinJ.... The engine is actually to short, i measured it up quickly yesterday and the cavitation plate is around 3 inch's above the transom of the boat.. I know this is a problem but there is no way im chopping the transom for this little motor, i do intent to go larger in the future and will hopefully use this as a back up.
 
Keep an eye on craigslist for a 20-35 hp long shaft jonnyrude with a blown powerhead or gearbox. you will have all the parts necessary to convert to long shaft. You need the extension housing, drive shaft, upper shift shaft and water tube.
 
I do have a mercury 40 that I've been given that has a longer shaft so I'm going to attempt getting that running. I also live on a small island in Spain so parts are harder to come by here and if ordered take a lifetime to arrive

Thanks
 
antjacobs said:
Hi all thanks for all your reply's....

KevinJ.... The engine is actually to short, i measured it up quickly yesterday and the cavitation plate is around 3 inch's above the transom of the boat.. I know this is a problem but there is no way im chopping the transom for this little motor, i do intent to go larger in the future and will hopefully use this as a back up.
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Then it's quite possible the prop is cavitating which would explain the poor performance. A long shaft motor is definitely needed for your boat.
 
Hello everyone!

I have a similar problem as orginally in this thread. I have an old 13ft(4m) fiberglass hull with very slight v-chape bottom and an 1977 25hp Evinrude with 9x9" prop. Can't say much about the weight, but the boat is an console boat(very lightweight consol of 2mm aluminium) but has an quite heavy plywood floor, 80 amp battery(under the console), 25 liter(6.6gal) tank in the rear and an electric trolling motor also in the rear. Havn't tested the boat alone, always had an passenger with me, weight about 440lbs plus fishing gear and water. The boat lifts up on plane quite easily but the top speed seems little slow. Measured with GPS only 28.5km/h(17.7mph).

Here is an picture of the boat, as you see front seat is quite in the front.

boat_with_evinrude_25.jpg


What do you think, is it normal performance for this boat and load?
 
The speed seems to be an issue with the boat it self, not the motor. Testing now with an old Suzuki 60hp and top speed is only 47km/h(29mph) with two persons on board. Maybe the weight is just too much in the front and the hull is old design and doesn't glide very well..? Engine sits on a 5.9" setback plate, cavitation plate is 2.4" above the keel. Any thoughts?

fishing_boat_with_suzuki_outboard_testing.jpg
 
With the 60hp you should be hitting the high spots of the waves. Have you checked the double bottom for water? Tap on the deck with a hammer all over the place looking for dryrot. You will hear the tone difference if there is rot under the fiberglass. Have you tried different trim angles? That hull should plane just fine i suspect a water soaked doublebottom. Those older boats used crappy foam that gets water soaked. The only way to fix it is to cut the deck out and chip the foam out. Alot of fiberglass on those older boats also it is sitting pretty lpw in the stearn you possiblycan shof some weight forward to bring the bow down if you cannottrim the motor down far enough.
 
Thanks for the reply. In fact this boat is from the age before the foam was invented. It's a single shell bottom with just an .6" plywood as floor. All water that gets in also get out from the rear drain plug. The fiberglass bottom has been reinforced with few layers of fiberglass. The boat feels quite heavy though, but it's still easy to winch(hand winch) up on the trailer. The motor has electric trim so yes, it gains about 2-4mph of speed when trimmed up close to the level where the prop starts to cavitate. The hull is missing the strakes, can this be the reason?
 
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