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4.3l Not reaching full speed?

R

robertshep43

New member
Just bought a 89 Baja 190 with a 4.3l

HISTORY: previous owner said he got the boat to 50MPH last summer and hasn't changed anything on the boat besides the prop.

Took it out the first time and sat around 35mph at 4500rpm, no problem getting on plane or running.

Thought this was slow, and noticed the dip stick being pushed out a few inches a couple times when stopping and doing boat cleanup, so checked the compression and all cyl read 190-200psi with one reading 155psi. Took it back out having done nothing besides the compression test, raising the tabs (i have manual ones and someone said they were slowing the boat down), and switching to the original 21p prop from a new one the old owner put on. The boat struggles to get going. Only got up to 30 and then to 35 if a trimmed (still not good with this and how to do it). Overall the boat seemed like it ran worse and slower.

so many factors to look at I dont know where i should really be looking. I am doing a tuneup tonight with plugs, wires, cap, and checking fuel filter/ system maybe.
 
I would discount what the previous owner said unless you witness it...

First thing you need to do is to get the correct prop so the engine achieves its rated WOT RPM...and changing lots of things will only add to the 'so many factors' issue...

what pitch prop was on the boat when you did your tests...?

the one cylinder with the low compression may limit the engine's performance in the upper RPM range...it may warrant further investigation to get everything dialed in...
 
Ayuh,..... Did the tune up help,..??

Did you examine the Contents of the fuel filter, for anything but clean fresh gasoline,..??

I too, think the p/o's opinion is abit optimistic,...
 
I also doubt that will hit 50. to the OP are you getting these speeds on a GPS or in tach speedo? If the in dash speedo yes PO may have hit 50 on what many call the dreamometer. My boat often reads 55 mph when on GPS I have never seen more than 48
 
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