Losing rpm's+mph

[Dave Abrahamson]

Hey all 1st time poster here in i/o.
My BIL (up in NH, so too far away for me to be of much help except for you guys here on the forums),has a Trophy 2052 cuddy w/ a 4.3 merc that has lost about 6-800 rpm's wot. 45mph down to around 30ish mph.
His mech said to drop from a 19p to a 17p prop, but it has run fine for the last couple years with the 19p. I said to look for another mechanic.
I have never wrenched on an I/O so what are some of the obvious things I sould tell him to look for? Plug wire? Gas filter?Throttle cables? Why would his mechanic want him to change props when the current prop has been operating fine for a couple of seasons?
Sorry to be so long winded, but I told hm if I were able to find help anywhere.....it would be on Iboats.

Thanks guys...he'll be reading this I hope.

Dave

 

[JustJason]

Re: Losing rpm's+mph

Start with the basics, do a compression check and a spark check to make sure he hasn't lost a cylinder. Double check the advance timing (although if no ones touched it, it shouldn't change). If that all checks out then on to the fuel system. I'd put a vac gauge along with some clear line inline to check for restrictions and air.
Where abouts in NH is he? he could always call me

 

[Dave Abrahamson]

Re: Losing rpm's+mph

Hillsborough.....a good haul from you probably.
Betcha there's a good fishin' trip in it for ya if ya fix it though.

 

[ziggy]

Re: Losing rpm's+mph

here's a real good list to go through. check out post #2....

http://forums.iboats.com/showthread.php?t=208547

go through that, one by one, and i'll bet ya find the problem....

 

[JustJason]

Re: Losing rpm's+mph

Hillsborough is to far for me....
Now if it was in hillsborough county..... then he'd be my neighbor

 

[Dave Abrahamson]

Re: Losing rpm's+mph

Thanks anyway CaptJason, nice to know there are people out there willing to help out a stranger in need. Ziggy, good post, thanks for the link.
Hope he finds the problem....it fishin' season up there...if I remember correctly, it only lasts a couple weeks in NH

 

[Coors]

Re: Losing rpm's+mph

That Don's link will usually get you going.

 

[DDAADDYY]

Re: Losing rpm's+mph

If you checked out this post, it sounds exactly like my woes, I've just now settled them up so hope this helps.
http://forums.iboats.com/showthread.php?t=251255