2.5 efi pistons

scooby_hugh · 10-08-2009, 05:30 PM

Does anyone know how long a 2.5 efi would last if i had the pistons top pinned ? Would the rings need doing every 100 hours or less, also what else do you change when rebuilding? Reeds and clean injectors? Anything else? Im thinking of this for a phantom 18 so it wouldent be caned as hard as others and would only do a few basic races the rest leisure, im not scared of rebuilding/having it rebuilt i know its a race engine

Burty · 10-08-2009, 08:57 PM

by having them top pinned it doesn't make them last longer between rebuilds, it just means you would probably be able to replace the rings and go again without the expense of replacing pistons. I wouldn't risk going more than 50 hours between rebuilds as any longer and you are on borrowed time and likely to end up with a viewing window in your block

scooby_hugh · 10-08-2009, 11:52 PM

ah okay fair enough, and what does the rebuild consist of? have mercury stated a list of things to check/replace at certain hours or do you just do the rings until something else goes and fix it?

roofer · 11-08-2009, 08:16 AM

A respected American engine builder { not jsre } told me rings would last upto 150 hours between rebuilds depending on how hard you use your engine.
If nothing is damaged you will get away with just replacing the rings and a gasket set but I always get the injectors serviced .

scooby_hugh · 11-08-2009, 09:44 AM

Quote:

Originally Posted by roofer

A respected American engine builder { not jsre } told me rings would last upto 150 hours between rebuilds depending on how hard you use your engine.
If nothing is damaged you will get away with just replacing the rings and a gasket set but I always get the injectors serviced .

The engine wont be being used hard as the boat will only do a couple of basics and the rest leisure so for the sake of saving fuel it will not be ragged 24/7, are the merc pistons and rings the best to get or are there better aftermarket ones like wiesco or similar?

roofer · 11-08-2009, 09:58 AM

I always used the early Mahle pistons and gold rings, the Yanks reckon the pins come out but i've had 7 2.5 efi's and never lost a pin.... I learnt an expensive lesson with my first efi so always get the rings replaced before I run the engine unless I know the history. It seems if you don't rev over 7500 the engines last a long time but the higher you rev em the shorter they live.

scooby_hugh · 11-08-2009, 01:41 PM

cheers for the responses, 7500 rpm sounds a good place to start or just below as the boat would be quite overpowered anyway so wouldent be looking to get every last bit of power right away, are gold rings the most durable then? and where is a good place to get the parts and prices?
cheers

roofer · 11-08-2009, 04:15 PM

On my P18 with 2.5 efi I used to rev up to 8500k with a 26 Yam drag prop and it handled great ... Buy the rings in the States I think retail for the gold rings in the UK is around £750 a set, less than half in the States.

scooby_hugh · 11-08-2009, 10:58 PM

what was the top speed on your 18 with the 2.5? was it a 260 or 280hp model? cheers

roofer · 12-08-2009, 07:38 AM

It started life as a 2.5 260 but I spent a fortune having it modified to way over 300hp. I had the mad intake and mad adjustable ecu, ported , exhaust chest work, high compression heads etc.
Like I said earlier I learnt an expensive mistake, it was so unreliable and I ended up rodding it but it was so fast it was scary.

scooby_hugh · 12-08-2009, 01:22 PM

sounds awesome! would you reckon id be better off with a promax 225? or would that be abit slow compared to a 260 or 280? thanks for the good answers its really helpful!

roofer · 12-08-2009, 01:48 PM

Quote:

Originally Posted by scooby_hugh

sounds awesome! would you reckon id be better off with a promax 225? or would that be abit slow compared to a 260 or 280? thanks for the good answers its really helpful!

Never owned a Promax but believe they are a strong reliable motor. Send Hydrostream a pm he's just bought one .

Jay Smith · 12-08-2009, 06:09 PM

TiN faced piston rings on the Nicom bores usually last 120-140 hours according to the use and abuse. Quality lubricants can extend the life also...

Jay Smith @ JSRE

Jon Fuller · 12-08-2009, 06:12 PM

Welcome back to the forum Jay.

jf

Jay Smith · 12-08-2009, 06:13 PM

Glad to be here Jon ... I'm here to visit, help and learn...

Jay @ JSRE

scooby_hugh · 12-08-2009, 09:37 PM

cheers for that, where would i get some tin faced ones from and how much would a set cost? How come some people on here are saying rebuild every 25 hours and some are saying 100 etc? if i know i can get 100+ hours out of the 2.5 i would be happy to use that, otherwise i might have to look into a promax

Jay Smith · 12-08-2009, 10:45 PM

What is your bore make up ( Cast Iron, Nicom/Nik , or chrome )? What motor are you running and what type and or brand of piston are you running ?

If you are running cast iron bores I suggest a Chrome faced ring, if you are running Nicom/Nick over an aluminum bore I suggest TiN ( Titainum Nitrate ) if you are running chrome I'd suggest a Cast Iron ring... These suggestions are the industry standards and come in the engines with the bores I sited...
ALL the 260,280, Drag, and 245 HP engines I build ( 1 to 3 engines a week ) with good nicom/nik coating and the bores are round ( No egg , my target is 1/2 a thou. outta round any more I bend them straight ) honed properly and use the correct break in methods with petrol. oil for the first hours will yield 130 - 140 hours of service...Thats been my engines life spans...

25 hours life span on a set of rings is very short lived. Maybe a champ motor with single rings?????? A double ringed TiN faced ring will live longer than that if the above methods are followed..

Good luck,
Jay

scooby_hugh · 13-08-2009, 12:00 AM

cheers, thats some very helpful info, i havent got an engine yet im still deciding which one to get, what year and type of 2.5 will have which bore?
thanks

Jay Smith · 13-08-2009, 12:32 AM

99% of all 2.5 High Performance Engines are aluminum sleeved and Nic/Nicom plated and forged piston equipted. The Pro Max is the other 1% and is a steel sleeved engine with cast aluminum pistons. Steel sleeved bored engines will last 4 time longer on a set of rings than coated sleeved engines . BUT the friction or drag is more on steel and they are not the power house monsters the coated sleeved engine are stock...

Jay

scooby_hugh · 13-08-2009, 12:43 AM

so would a promax 225 be able to be tuned to 250hp or a 280 efi be detuned to 250hp (probably just by limiting rpms) which would last the most hours roughly?