350 mag mercruiser

[blackleytroy]

Re: 350 mag mercruiser

These figures were with 2 of us in the boat and a full fuel tank (about 65 gallons). I used a snap-on portable tach. I will check the timing and may do a thorough tune up this winter while it is in my shop for the winter. The recent trip at 5000 ft was an exception, we typically boat at much lower altitudes and so this may also make some difference. Thanks for all the help and I guess the prop isn't so bad and will check it again next spring after the winter tune up.

 

[Tail_Gunner]

Re: 350 mag mercruiser

I am sorry if this is frustrating but it can bge a adventure as well if you like to tinker that is. There is a very spefic method to timing your engine if it is a mefi 3 which is more that likely...There are manuals in the i/o forum i believe you need a shunt to short the base timing to set it properly

 

[QC]

Re: 350 mag mercruiser

The recent trip at 5000 ft was an exception, we typically boat at much lower altitudes and so this may also make some difference.

It is a HUGE difference depending on what your normal altitude is. Don't change anything based on your high altitude results unless you are tweaking for that altitude. Fuel mixture and prop both require high altitude changes.

 

[John_S]

Re: 350 mag mercruiser

I am sorry if this is frustrating but it can bge a adventure as well if you like to tinker that is. There is a very spefic method to timing your engine if it is a mefi 3 which is more that likely...There are manuals in the i/o forum i believe you need a shunt to short the base timing to set it properly

His '92 carbed 350 Magnum is probably thunderbolt IV ignition, unless it was changed. If so, no shunt or base mode to worry about.

While merc probably had carb jetting recommendations for high altitude, I wouldn't bother unless all or most of your boating is that. A lower pitch prop to better handle the high altitude vacations is simple enough to change. It could always double for the low altitude tear your arms out water ski prop.

 

[QC]

Re: 350 mag mercruiser

I agree ^^^^^ My post should've said "if you plan to stay at that altitude" or something like that . . .

 

[Tail_Gunner]

Re: 350 mag mercruiser

:facepalm: Smiles the mag threw me off thought it was a 03.... However i still believe the boat has a engine issue...22' cuddy 1.5 gearing 15 or 16" prop with a light load and 0% slip....Way to much going on there...A simple plug read would do a lot...AKA are they white brown or carmel...

 

[John_S]

Re: 350 mag mercruiser

Baring measurement errors, zero slip, I want some. OK, probably only if it takes me to higher wot speeds.

Given the large diameter for an I/O, I am thinking this is a specialized prop, like "big ear", made for larger, heavier cruisers. I have no experience in running that style, that would justify a zero slip number. But, maybe there is some form of cupping that would normally make it act like more pitch???

I would think, an established california prop shop should be able to determine what he has and have allot of experience with dealing with elevation change. While you won't get an iBoats online discount, buying the right one the 1st time, is probably of more value.

 

[blackleytroy]

Re: 350 mag mercruiser

Interestingly enough, we bought the boat out of Las Vegas and prior to that, it was in California. Perhaps I should contact a prop shop there? I will do some tuning over the winter and then try it again in our usual lake, at much less altitude.
Thanks