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b79 100hp V4 Evinrude acceleration problems

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leeknudsen

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"Hopefully I can find at least

"Hopefully I can find at least an idea to my problems, so here I go;

I have a 1979 100hp Evinrude V4, on a 1980 16.5 Wellcraft tri-hull, that I recently bought. Boat and motor sat up for just short of a year. However, Motor starts fast and idles smooth. I have good compression in all cylinders (about 105 in 3 and 110 in 1). when flushing, the boat runs fine, accelerates fine, but when I put the boat in the water, and it's under load, it seemed to be real slow to accelerate. So I took the carbs off to clean, and replaced some fuel lines and such. Next time I put it in the water I'd put the throttle forward, and the engine reved much quicker, but then "Bogg" and rev and bogg so forth. The water was very, very choppy(3-4 ft w/ whitecaps) But after a couple of minutes, it's like the propeller caught some water and the boat took off fast, faster than I've seen it move yet. I've been told everything from stator problems to propeller cavatation. There are also some after market hydrofoils mounted above the propeller. When the water is smooth the boat doesn't seem to have nearly as much trouble taking off. I haven't been able to try it on flat water since I cleaned the fuel system. Any ideas????"
 
Well I guess if it does get up

Well I guess if it does get up and run after awhile it must be running ok. I'd check that there is not to much pitch on the prop and check for water in the bottom of the boat if it has a false bottom. Sometimes water can get trapped under the floor and really make it hard for the boat to get on plane. If its on a trailer try lifting the trailer up and down and listen for water moving in the boat. Check that there is not to much weight in the back of the boat. Like batterys fuel tanks etc. If that fails try removing the hydrofoil. You are not real clear on just how it takes off in flat water. If it has some of the same bogg / slip and grab as you have in rough water or not. If it does not have the same problem in flat water the hydrofoil could be the problem by letting the prop grab air from under the hydrofoil in the rougher water. You may also want to check the spark plug condition and if they are the correct plugs for the engine and check the timing and carb adjustment. Just a thought or two but without seeing what is going on it is hard to tell. Best of luck.
 
Strange problems continue with

Strange problems continue with Starboard 150 Evinrude Ocean Pro 1997 (850 hours)- RPMs woould not lift above 4000 and it seemes the throttle was kind of tight as I would shift to forward -yesterday after hours of fishing started the engine no forward or reverse assumed a spun prop or something of that nature. Well back at the dock tried again lo and behold got some forward and reverse than a cable pops right out of the engine- looks like a screw (at the end of the cable) was sheared off- also looking at the thin cable there was a slight kink-assuming the cable is the answer can I replace just the fitting the screw at the end or is this an entire cable replacement. Question 2 since this has just occurred might this explain why my throttle to that engine seemd tighter than normal and restricted the rpms just curious if there was a link there regards Gary.
 
"Korbel:
You have 'stolen

"Korbel:
You have 'stolen' another post, could You please move to a new post by starting a new thread."
 
":::UPDATE:::

First, thanks

":::UPDATE:::

First, thanks to all those who replied!!

I finally was able to try it on flat water. The boat, however still real slow to accelerate, got on plane with no problems. No revving, or bogging. the boat begins to plane at about 2700 rpms, and get the best speed at around 4000. The info plate on the motor says that optimal operating rpms should be around 5500, strange the most I can get is 4300, any higher and I start loosing speed due to too much prop being out of the water. At WOT the motor runs very smooth and quite, and (if my depth/fish finder is correct)I'm moving about 29-31 MPH. Now, I'm not a outboard motor scientist, but I'd figure that a 100HP motor should be able to push a 16 foot boat a little faster than 30mph (tri-hull or no). Also My prop is currently a 13X19P(info engraved on outside of prop), but around the center of the prop it says 13 3/4X17. Leads me to think that the prop has been worked on, or is not the original prop. Guy at the local prop shop says that a 17P to 15P would "grab" more water, make me plane faster, giving me better hole-shot(not sure what that is), and somehow making my over all speed faster? Not sure how that works, but ok. So I'm going to try a couple of things (like taking a look at those cables that guy was talking about, mine look adjustable),maybe a new prop, then as a last resort...off to the shop.

Any thoughts?? At least when this is all said and done, I should be somewhat knowledgeable about my boat motor...LOL"
 
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