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Sunrunner 240 sb 151a aq 290

T

tlacey1

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"hi all i have been lurking fo

"hi all i have been lurking for a while now.have some questions,i have a sunrunner 240sb with a 151a/290 sp leg long hub.so far what i have done added a dowel fin hot spark ign,tuned the engine again and again the carbs are fine (twin solex).tried a 14x17 15x17 ended up with a 16x12 prop now hers my problem i cant go over 20 mph.with the 14x17 i got like 10 mph at 4600 rmp,the 15x17 18 4500-4700 rpm,the 16x12 20 at 4800-5000 rpm.and of coarse with these props i have only idle or wide open.when i fall from 4000 rpm the boat falls off from plane????? any help its out of the water for the season and i want to make it better for next year.i talked to the prior owner he says 30-35 mph he used to go ????"
 
"Tom, one thing I can tell you

"Tom, one thing I can tell you is that your boat is clearly underpowered and you cannot expect much from a 146 HP engine on a 24' boat. If you search the web, you wil see that most boats that size (including Sunrunners) do have 350 Chevs or 351 Fords installed; that is, power plants with 250-300HP output. Also, it is not uncommon for some previouos owners to fudge speed and other figures to make the sale more attractive; some of them even believe their own fantasies. In any case, in view of the figures you posted, I would try a 15 x 15 cupped, wide blade propeller; and if you reach about 5000 RPM with it, that's probably about as much speed as you are going to get. A set of trim tabs may only help if the boat is not correctly trimmed.

Sorry, but if you want more speed, the only thing I can advise you to do is to repower, and that won't be cheap."
 
"i do have trim tabs,i had my

"i do have trim tabs,i had my 16x12 cupped last year and it was bad no speed at all like 17 mph.i know its under powered but is it going to hurt the engine going 5000 rpm for like 3 hrs straight???"
 
"Tom, the only reason I can im

"Tom, the only reason I can imagine (and I admit in advance that I could be wrong) why the boat ran faster with the uncupped prop is because of an increase in engine RPM after the cup was removed.

And no, I don't think you will hurt the engine by running it for 3 hours at 5000 RPM as long as the coolant temperature remains constant and not over about 200ºF."
 
"You need 190 HP to go 30-35 m

"You need 190 HP to go 30-35 mph. This would be a Ford 302 or GM 305. Installing small engines became a customer sales point during the first oil crisis. From time to time, somebody still buys the idea that a very small engine will save gas on a planing boat. Don't work that way and results in some frustrations."
 
"ohhh btw i installed the hot

"ohhh btw i installed the hot spark ign earlier this season and it started and ran better with the old points.yes el i set the timing and rechecked it 3 times and yes it does advance (its not stuck) im going to try a replacement next season if that does not help im going back to points.and yes i love the boat its the perfect family cruiser even though it dose not go fast all my friends call it the big bathtub.well its out of the watter bottom cleaned winterized and covered for another year,did not have time this year to go to the thousand islands boy am i pissed this business sucks!!!"
 
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